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Latest ATAP News


Director’s Corner

Cameron Geddes, ATAP Division Director

The advanced hardware that is foundational to accelerators is highlighted by our two research features this month. Parlaying our accelerator controls and instrumentation expertise into advances in quantum information systems, a team of ATAP Division physicists and engineers at Berkeley Lab has demonstrated the feasibility of low-cost and high-performance radio frequency modules for qubit controls at room temperature. Meanwhile, our laser researchers continue to advance in their efforts to coherently combine pulses from fiber lasers, with the goal of producing high-energy, high-repetition-rate beams for future laser-plasma accelerators (LPAs). This is a frontrunning candidate for kBELLA, the proposed next-generation laser that will enable practical applications of LPAs. We had an opportunity to brief Deputy Secretary of Energy David Turk on these matters during his recent visit to Berkeley Lab.

Theory and computational modeling have always gone hand in hand in ATAP. Our Accelerator Modeling Program had the honor of authoring a paper and co-authoring another in the latest issue of the ICFA Beam Dynamics Newsletter.

Helping plan the future of high-energy physics, our staff are participating extensively in the Snowmass process, now taking place.

The Berkeley Lab Director’s Award for Scientific Achievement went to Chad Mitchell of the Accelerator Modeling Program, and Soren Prestemon, Deputy Division Director for Technology and head of our superconducting-magnet programs, joined the ranks of our Fellows of the American Physical Society.

As the year comes to a close, I would like to thank everyone for continuing to make progress under the difficult circumstances of the pandemic. I wish you a safe, restful, healthy, and happy holiday break, and look forward to another year of exciting research and development in 2022.



—Researchers build an open source room-temperature control system for superconducting quantum processors

By Monica Hernandez, Quantum Communications Lead, Computing Research Division

RF mixing modules

RF mixing modules for electronic controls of superconducting quantum processors. (Credit: Gang Huang and Yilun Xu/Berkeley Lab)

A team of ATAP Division physicists and engineers at Berkeley Lab have successfully demonstrated the feasibility of low-cost and high-performance radio frequency modules for qubit controls at room temperature. They built a series of compact radio frequency (RF) modules that mix signals to improve the reliability of control systems for superconducting quantum processors. Their tests proved that using modular design methods reduces the cost and size of traditional RF control systems while still delivering superior or comparable performance levels to those commercially available.

Their research, featured as noteworthy in the Review of Scientific Instruments and selected as a Scilight by the American Institute of Physics, is open source and has been adopted by other quantum information science (QIS) groups. The team expects the RF modules’ compact design is suitable for adaptation to the other qubit technologies as well. The research was conducted at the Advanced Quantum Testbed (AQT) at Berkeley Lab, a collaborative research program funded by the U.S. Department of Energy’s Office of Science.

“This is an outstanding example of how expertise built up for one area of science, such as instrumentation and control of particle accelerators, can have benefits reaching across disciplines,” said ATAP Division Director Cameron Geddes.

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A Question of Scale

Despite significant advances in building processors with more qubits, which will ultimately be needed to demonstrate a quantum advantage over classical computers, quantum computers continue to be noisy and error-prone. Each additional qubit introduces new layers of complexity and possibilities for electrical failure, especially at room temperature. This growth in complexity and computing power requires a rethinking of certain core control elements.

Traditional RF control systems use analog circuits to control superconducting qubits, but they can become bulky and overwhelmingly complex, thus serving as a potential point of failure and increasing the costs for hardware control. AQT researchers Gang Huang and Yilun Xu from Berkeley Lab’s Accelerator Technology and Applied Physics Division (ATAP) demonstrated a new way to control qubits that is already enhancing other quantum computing projects at the testbed’s user program. The team substituted the larger, more costly traditional RF control systems for one built at Berkeley Lab, which uses smaller interactive mixing modules.

A key aspect of this modular system is delivering high-resolution, low-noise RF signals needed to manipulate and measure the superconducting qubit at room temperature. To do so, it’s important to shift the qubit manipulation and measurement signal frequency between the electronics baseband and the quantum system.

“The new module exhibits low-noise, high-reliability operation and is now becoming our laboratory standard for microwave frequency modulation/demodulation across many different experimental configurations in AQT,” Huang explained.

Using the team’s low-noise RF mixing module to shift the bandwidth with a limited intermediate frequency between the electronics baseband and the quantum system intrinsic band allows researchers to utilize less noisy converters for better performance and at a lower cost.

Huang and Xu said that while their system was designed for superconducting systems, it could be expanded to other quantum information science platforms. “In general, the architecture of RF mixing can be expanded to higher frequencies,” they noted. “Therefore, if we replace some electronic components with appropriate frequency, this kind of compact design should be able to adapt to the other qubit platforms, i.e., semiconductor qubit systems.”

Researchers also designed electromagnetic interference shielding to eliminate undesired perturbations, which reduce signal integrity and limit overall performance. This shielding aims to prevent the signal from leaking out and interfering with surrounding electronics – a common problem for quantum computers.

RF mixing modules

Left: AQT cryogenic dilution refrigerator. Right: Two kinds of RF mixing modules: the up and the down converter. (Credit: Gang Huang and Yilun Xu/Berkeley Lab)

Open Source, Open Hardware

With the release of a control system that is open source, the team hopes that the broader community uses and contributes to the repository, improving the hardware. By replacing a few electronic components with appropriate frequency, this kind of compact design may adapt to a variety of quantum computing facilities.

“This is one of our first efforts to develop an open source control system for superconducting quantum processors,” explained Huang. “We will continue to optimize the physical size and cost of the module and further integrate with our FPGA-based controller to improve the extensibility of the qubit control system.”

Looking ahead, the researchers are already building on these efforts to create new possibilities in quantum computing and offer a new technology to control qubits.

“Such integration and optimization will help room-temperature-based control systems keep pace with advancements in the complexity of quantum processors,” noted Xu.






—Gordon and Betty Moore foundation grant is latest impetus to program in high-average-power lasers

By William Schulz

The next phase in the development of laser-plasma particle accelerators (LPAs) — potentially game-changing tools for research and practical applications — is underway in ATAP. A new approach to high-power lasers — combining the pulses from many fast-acting but lower-energy optical fiber lasers — will energize these super-compact accelerators.

Berkeley Lab researchers have zeroed in on the limitations of today’s LPAs and believe that high-repetition-rate systems using optical fiber lasers are the path to increased stability and performance as well as higher pulse rate.

Tong Zhou at a beam combining experiment

ATAP Division research scientist Tong Zhou conducting fiber laser combination experiments. An ongoing multi-institutional project to coherently combine the output of fast-pulsing but low-energy fiber lasers could be the secret to having both high energy and high repetition rate — key to the next steps in laser-plasma accelerators. (Credit: Marilyn Sargent/Berkeley Lab)

Cameron Geddes, ATAP Division Director, said, “Based on recent technological breakthroughs in fiber lasers and laser-plasma accelerators, it’s time to bring these together—to develop a next generation of compact and precision-controlled accelerators that can bring new capabilities to a wide range of applications.”

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LPAs: Small is the new big

LPAs, in which ATAP’s Berkeley Lab Laser Accelerator (BELLA) Center is among the leaders, are a radically compact approach to particle acceleration, notable for achieving particle energies in centimeters that would require tens of meters with conventional technologies.

Conventional accelerators use microwaves in resonant metallic cavities to impart high energies to beams of subatomic particles. This mature technology, which can take several circular or linear forms, makes accelerators powerful engines of scientific discovery, in addition to numerous practical applications in medicine, industrial processing, and national security. Many of them are, however, large and costly.

LPAs offer an alternative way to accelerate and boost the energies of the particles. Rather than using microwaves, an intense beam of laser light fired through a gas will generate a plasma wave that charged particles can ride like a surfer.

Radically smaller than present-day means of achieving the same beam energy, LPAs would be attractive in many applications, ranging from biomedical treatment to free-electron-lasers research centers to nuclear nonproliferation. Ultimately they might even be the basis for a new generation of colliders, orders of magnitude smaller than today’s, for high-energy physics.

LPAs have been successfully demonstrated (BELLA Center holds the record, having accelerated electrons to an energy of 7.8 billion electron-volts in just 20 cm), but they require high laser power. A laser like the BELLA Petawatt produces output greater than to the entire output of the world’s electrical grid for an extremely brief instant, focused into a pulse the diameter of a human hair. However, it can only muster a pulse every second or so. Useful applications will require high laser power delivered in much more frequent pulses. That’s where the new fiber laser project comes in.

Laser teamwork means powerful pulses

Fiber lasers (based on optical fibers that are like those familiar from telecommunications and computer networking, but designed for optimal laser emission) are fast, but small. Each optical fiber provides a channel no wider than a human hair, and can only emit so much power. The project now getting underway—building upon several years of groundwork at Berkeley Lab, the University of Michigan, and Lawrence Livermore National Laboratory—will further develop a scheme called “coherent beam combining.” The goal is pulses energetic enough to drive an LPA, but delivered a thousand times a second.

The new project is led by ATAP Division researcher Tong Zhou. Berkeley Lab team members working on fiber laser development also include Russell Wilcox, Qiang Du, Thorsten Stezelberger, and Jeroen van Tilborg. Almantas Galvanauskas and his students at the University of Michigan and Leily Kiani at Lawrence Livermore National Laboratory also play important roles in the program.

The overall effort, continuing to build upon several years of progress, involves spatial, temporal, and spectral combining in a way that preserves “coherence” (a distinctive quality of laser beams, necessary for LPAs). It aims to bundle the relatively low-powered pulses from many fibers into 30-50 femtosecond long, 200-millijoule pulses with peak power much greater than one terawatt. This would be the highest energy and peak power ever obtained from a fiber laser, and more than sufficient for demonstrations of laser-plasma acceleration.

“Their power consumption would be improved compared to conventional lasers, and their ability to dissipate heat is excellent, addressing other challenges in building high-power lasers,” Zhou said.

Schematic of beam combining experiment

Combining laser beams so that they truly resemble one powerful beam is challenging. The next steps being taken by the project that recently commenced, headed by Tong Zhou and supported in part by the Gordon and Betty Moore Foundation, will build upon existing work on spatial combining, as well as amplification in doped fibers. Spectral beam combining (the subject of Zhou’s prestigious Early Career Research Program award from the Department of Energy’s Office of High Energy Physics) and temporal stacking are other ongoing aspects of the overall effort to produce a high-power kilohertz beam from fiber lasers. (Credit: Russell Wilcox, Tong Zhou, Cameron Geddes (Berkeley Lab); Almantas Galvanauskas (University of Michigan).

The long-term goal is a collider for high-energy physics. For those purposes, an LPA would need laser energy on the order of 10 joules in short pulses (30 to 100 femtoseconds each), with a repetition rate greater than 10,000 pulses per second — specifications far beyond existing laser technology. Fiber lasers are a promising candidate for solving this problem, and could in the meanwhile power the many spinoff applications of LPAs.

Power isn’t the only important thing in a system that has to deliver a hair-thin beam into a capillary with an inside diameter just a few times larger than that. Measurement and active feedback for precision control of such attributes as pointing angle and position are the subjects of complementary work at BELLA Center. Machine learning is emerging as an important control technique, as highlighted in a recent article by Dan Wang of the Berkeley Accelerator Controls and Instrumentation (BACI) Program. Wang is pioneering new techniques important to both particle accelerators and fiber lasers, as part of a program with Qiang Du and others.

“We want to not only build a laser system that sets power and energy records, but also state-of-the-art controls, then use it to realize the first high-average-power, high-repetition-rate, laser-driven accelerator in the world,” Geddes said.

Such a system, coherently combining ultrashort pulses from many fiber lasers at a kilohertz repetition rate, is a frontrunner for the laser technology of kBELLA, the proposed next generation of the Berkeley Lab Laser Accelerator (BELLA) Center’s LPA drivers, as well as a broad variety of other applications ranging from accelerators to material processing.

A newly awarded $2.4 million grant from the Gordon and Betty Moore Foundation, by way of the Berkeley Lab Foundation, will aid the coherent-combining work. The Gordon and Betty Moore Foundation fosters path-breaking scientific discovery, environmental conservation, patient care improvements and preservation of the special character of the Bay Area. Additional support is provided by the U.S. Department of Energy, Office of High Energy Physics Early Career Research Program and Accelerator Stewardship Program.




Deputy Secretary of Energy David Turk Visits BELLA Center

David Turk, second-ranking official at the Department of Energy, toured ATAP’s Berkeley Lab Laser Accelerator (BELLA) Center during his November 3, 2021 visit to Berkeley Lab. ATAP staff briefed him on the BELLA Center’s work to create a new generation of particle accelerators that are much more compact than conventional ones by using ultra-intense lasers to drive plasma waves. Topics included kBELLA, a proposed next-generation laser facility, and coherent beam combining, a candidate for one of kBELLA’s key enabling technologies. kBELLA would help make laser-plasma accelerators useful for applications.

Photography by Thor Swift/Berkeley Lab.

Michael Witherell, Natalie Roe, David Turk, Cameron Geddes view historic photos in BELLA hallway

L-R: Visiting the BELLA Center were Berkeley Lab Director Michael Witherell; Environment, Safety, and Health Division liaison to the Physical Sciences Directorate Herb Toor; ATAP researcher Tong Zhou; Senior Advisor for Nuclear Security Captain Sean M. Muth, USN; Special Assistant to the DOE Deputy Secretary Sandie Raines; Associate Laboratory Director for Physical Sciences Natalie Roe; DOE Deputy Secretary David Turk; and ATAP Division Director Cameron Geddes. They are looking at a photo of Laboratory founder Ernest O. Lawrence at the 37-Inch Cyclotron, part of a display of historical photographs in this area depicting our accelerator heritage.


“It was an honor to showcase our facilities and explain how the Division’s research benefits society,” said ATAP Director Cameron Geddes.

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Supplying high average power at the eponymous repetition rate of a thousand pulses per second, or a kilohertz (compared to present-day high-power lasers like the BELLA Petawatt, which fire a pulse per second), kBELLA will be able to drive the next generation of laser- plasma accelerators. This will open up their many applications, ranging from biomedical treatment to light sources for fundamental research and national security. Such lasers will also enable new industrial processes that create and measure the properties of materials needed for advanced manufacturing, energy storage, and carbon management.

David Turk and Cameron Geddes in BELLA laser control room

ATAP Director Cameron Geddes (right) shows Deputy Secretary Turk around the BELLA laser control room.


David Turk and Cameron Geddes look at capillary

In the BELLA Petawatt amplifier bay, ATAP Director Cameron Geddes (center) shows Deputy Secretary Turk (right) and Special Assistant Sandie Raines (left) one of the plasma capillaries in which laser-plasma accelerators can achieve energies in centimeters that typically require hundreds of meters in conventional accelerators. At right, the plasma capillary in use,
creating a plasma that can guide ultra-intense lasers, enabling plasma acceleration.

David Turk and Tong Zhou

ATAP Research Scientist Tong Zhou (r.) briefs Deputy Secretary Turk on coherent beam combining — a technique, being developed at BELLA Center together with colleagues from Lawrence Livermore National Laboratory and the University of Michigan, to assemble a high repetition rate, high average power laser beam from the fast-pulsing but low-powered beams of numerous fiber lasers. Such a laser is a frontrunner for kBELLA, a proposed shovel-ready project that could power the next generation of ultracompact laser-plasma particle accelerators.

To learn more…

See more of the Berkeley Lab endeavors that Deputy Secretary Turk visited.

Visit the kBELLA pages on the BELLA Center website.



AMP Researchers Featured in ICFA Beam Dynamics Newsletter

Pictures of ICFA Beam Dynamics Newsletter authors from ATAP: Jean-Luc Vay, Axel Huebl, Remi Lehe, Chad Mitchell, Ji Qiang, and Rob Ryne

AMP ICFA authors

The latest issue of the ICFA Beam Dynamics Newsletter has a thematic focus on advanced accelerator modeling. Of the six articles, one has a lead author (and two co-authors) from ATAP’s Accelerator Modeling Program (AMP); another has three AMP co-authors.

AMP head Jean-Luc Vay was lead author of “Modeling of advanced accelerator concepts.” Co-authors included AMP’s Axel Huebl and Remi Lehe.

Huebl and AMP colleagues Chad Mitchell, Ji Qiang, and Rob Ryne were among the co-authors of David Sagan (Cornell) et al., “Simulations of future particle accelerators: issues and mitigations.”

The newsletters, which appear a few times a year, are published by the International Committee on Future Accelerators Beam Dynamics Panel. ICFA was created in 1976 by the Particle and Fields Division of the International Union of Pure and Applied Physics (IUPAP) to promote international collaboration towards construction and use of accelerators for high energy physics. The newsletter series began in 1984 and appears in IOPScience’s Journal of Instrumentation. Yunhai Cai of SLAC was editor for this issue.




ATAP Leadership in Snowmass

Major ATAP Snowmass participants

ATAP researchers have several leadership roles in the Snowmass process

The “Snowmass process,” the community-input phase of long-term strategic planning in US high-energy physics, has extensive ATAP technical participation, with many ATAP and other Berkeley Lab co-authors of Letters of Interest and whitepapers. As the meetings themselves got underway beginning September 24, ongoing leadership roles came to the fore.

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Stephen Gourlay, former director of the division and now an active affiliate in retirement, is one of three co-conveners for the overall Accelerator Frontier. ATAP Director Cameron Geddes is a co-convener of the Advanced Accelerator Concepts topical group on the Accelerator Frontier.

GianLuca Sabbi of the Superconducting Magnet Program is a co-convener of the Magnets subgroup in the Accelerator Technology topical group, and Ji Qiang of the Accelerator Modeling Program is a co-convener for Theoretical Calculations and Simulation on the Computational Frontier.

Bringing early-career researchers into the planning process is an important part of Snowmass. BELLA Center’s Marlene Turner represents early-career researchers in the Multi-TeV Colliders topical group, and recently gave a talk on increasing the physics reach of future particle colliders by decreasing their energy consumption by implementing energy recovery methods, which are made practical by the high gradients of plasma based accelerators. Tianhuan Luo of the Berkeley Accelerator Controls and Instrumentation Program is on the Early Career Survey Team, and Axel Huebl of the Accelerator Modeling Program is Early Career Manager.

Liaisons from one topic to another are a key aspect of communication throughout the large, complex Snowmass process. Accelerator Modeling Program head Jean-Luc Vay serves as the liaison from the Computational Frontier to the Accelerator Frontier, and BELLA Center Deputy Director for Experiments is liaison from Community Engagement to the Accelerator Frontier. Berkeley Accelerator Controls and Instrumentation (BACI) Program head Derun Li is one of the representatives of the Accelerator Frontier in a new Muon Collider forum that combines the interests of the Accelerator, Energy, and Theory Frontiers.

The Snowmass process (named after its origins with summer studies in Snowmass, Colorado) is organized by the American Physical Society’s Division of Particles and Fields approximately every eight years. Delayed by the pandemic but persevering in virtual fashion, the process restarted in earnest September 24 and is now holding meetings that are expected to result in Topical Group reports early in 2022, then Frontier Reports, and finally, in autumn 2022, a summary report.

The resulting summary of the community’s views on the key questions of high-energy physics, and the technology possibilities for addressing them, will be taken into consideration by “P5” — the Particle Physics Project Prioritization Panel. P5 is a temporary subcommittee (reconstituted as needed on an approximately decadal basis) of the DOE’s High Energy Physics Advisory Panel, a standing committee that provides input to both the DOE and the National Science Foundation.




Recent highlights, in case you missed it…

A Tantalizing Look at Tantalum Telluride in HiRES

Schematic of UED TaTe2 experiment

Illustration of the optically pumped (with near-infrared femtosecond pulses), and ultrafast electron diffraction probed experiment.

Diagram of how the HiRES movie was made

An illustration of how researchers made a movie of the ultrafast melting process in TaTe2 using ultrafast electron diffraction at HiRES.

The High Repetition Rate Electron Scattering facility, developed by ATAP’s Berkeley Accelerator Controls and Instrumentation (BACI) Program and located at the Advanced Light Source (ALS), was used to perform the first-ever ultrafast electron diffraction studies of optical melting of tantalum ditelluride (TaTe2). Tantalum ditelluride is one of a class of materials called transition-metal dichalcogenides, studied increasingly over the last several years, that have interesting and potentially useful properties when formed into atomically thin monolayers.

The achievement, summarized in a Research Highlight by Berkeley Lab’s Molecular Foundry, also helps validate the scientific usefulness of this one-of-a-kind instrument, enabled by research that began with advanced photoinjectors for light sources. ATAP’s Daniele Filippetto, principal investigator of the HiRES UED beamline, is corresponding author of the paper in the Nature journal Communications Physics describing the experiment.

To learn more…
Seeing Atoms and Molecules in Motion with an Electron ‘Eye,’ a Berkeley Lab news release, described HiRES and the technologies that made it possible.

Khalid Siddiqui and Daniel Durham are the two lead authors of the Communications Physics paper. Khalid explains his research in this video from the 2020 Berkeley Lab Research Slam competition. Now with Aarhus University in Denmark, he performed this work as a postdoctoral scholar in Berkeley Lab’s Materials Sciences Division. Daniel is a UC-Berkeley graduate student, and he continues to work at HiRES, performing ultrafast experiments on novel materials.



How AMReX is Influencing the Exascale Landscape

— A Q&A with Andrew Myers, core development team member

Editor’s Note: The WarpX “code” (scientific computing program) from ATAP’s Accelerator Modeling Program has become invaluable for advanced accelerator simulations. This interview, from an article by Kathy Kincade of Berkeley Lab Computing Sciences, describes how the AMReX software framework for high-performance computing co-evolved with WarpX.

Andrew Myers

Andrew Myers

While the hardware components of exascale are key, so too are the software packages and frameworks that will support the demanding scientific applications that run on these next-generation computing systems, and beyond.

Since first coming onto the exascale scene in recent years, AMReX has blossomed into one of the key software ecosystems for many Exascale Computing Project (ECP) efforts, from WarpX and MFiX-Exa to ExaWind, ExaStar, and ExaSky, among others.

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AMReX — an open-source framework for performing block-structured adaptive mesh refinement calculations — is the result of a collaboration between Lawrence Berkeley National Laboratory (Berkeley Lab), the National Renewable Energy Laboratory, and Argonne National Laboratory, with development centered at Berkeley Lab. All three labs are part of the Exascale Computing Project’s (ECP) Block-Structured AMR Co-Design Center.

In this Q&A, Andrew Myers — a computer systems engineer in Berkeley Lab’s Center for Computational Sciences and Engineering and a member of the AMReX core development team — looks at how this unique HPC software framework has influenced and continues to influence, a broad spectrum of scientific applications, both within ECP and outside the ECP program.

How does the AMReX code help researchers at the exascale level, and what makes it unique among adaptive mesh refinement codes?

AMReX is a framework for performing block-structured adaptive mesh refinement calculations. It provides a set of multi-level, distributed data containers for mesh and particle data and handles things like parallel communication, GPU offloading, and inter-level operations so that applications don’t have to. It also has support for complex geometry through embedded boundaries and a variety of linear solvers.

I think a strength of AMReX is our readiness to adapt and to add functionality to support the needs of applications. We are always interested in growing our user base by supporting cool new application codes, and if there is functionality that doesn’t exist right now that would be generally useful, we are interested in helping you build it.

What applications is it most widely used for at present, and why?

AMReX (and its predecessor, BoxLib) have a long history with reacting flows in both the low-Mach-number and highly-compressible limits, and it supports a lot of research along those lines in combustion applications and in astrophysics. We also have a lot of experience with particle-mesh techniques in various contexts, going back to the Nyx code, which uses particles to model parcels of dark matter in an expanding background. Aside from those staples, there is a growing body of other application areas both inside and outside of ECP, ranging from fluctuating hydrodynamics to multi-phase flow problems, electromagnetics for microelectronic circuit design, wind farm modeling, and more.

What ECP projects currently utilize AMReX? Are some of these projects also part of NERSC’s Exascale Science Applications Program (NESAP)?

There are currently codes in six ECP application projects that “fully” use AMReX: Nyx in the ExaSky project, Castro in the ExaStar project, WarpX, MFiX-Exa, AMR-Wind in the ExaWind project, and PeleLM and PeleC in the combustion project. There is also a seventh project that has an additive manufacturing code called Truchas-AM, that we partially support; they only use the linear solvers in AMReX. Of these, WarpX is also a part of NESAP, and it has benefited greatly from the collaboration, particularly in regards to a load-balancing project led by former NERSC postdoc Michael Rowan.

With the advent of Perlmutter and the first exascale systems, how is AMReX adapting to these new GPU-dominant platforms?

At the start of the project, we knew GPUs were important, but we also figured that one of the eventual exascale machines would be a many-core CPU architecture, kind of like Cori KNL or the ARM-based Fugaku machine in Japan. Events unfolded differently, and we ended up needing to accelerate our GPU efforts to prepare for machines like Summit, Perlmutter, and Frontier. Much of the core AMReX framework has been redesigned to work well on GPU-based machines.

A big part of this process was the decision to move away from Fortran towards a pure C++ codebase. We resisted this at first – most of us were big Fortran fans, and in many ways, it is an ideal language for technical computing. But the tools for adding GPU support to a complex framework like AMReX, in our opinion, were better in C++, and with modern compilers that support the __restrict__ keyword the performance edge that Fortran enjoyed for CPU execution was eliminated, so we made the transition.

Compared to the work needed to prepare for Summit, gearing up for Perlmutter and Frontier has been relatively pain-free. Part of that has certainly been due to the expertise and computing——— resources made available to us through NERSC and the NESAP program.

How has AMReX influenced the development of WarpX?

AMReX and WarpX have really grown up alongside each other. We have a tightly-coupled development model (I personally split my time 50-50 between both codes), where the needs of WarpX drive AMReX development, and things we develop for WarpX that we think will be useful for other applications end up getting migrated to AMReX. For example, there is a function parser that was developed for WarpX by Weiqun Zhang, another AMReX developer, that performs the run-time evaluation of mathematical expressions written in plain text by WarpX users on both CPUs and GPUs, without any need to recompile either WarpX or AMReX. This is really hard to do well, especially with GPUs (my advice on this, by the way, was “don’t do that” — I guess I was wrong!) This was recently migrated from WarpX to AMReX so that other application codes can take advantage of it.

What are some tangible benefits that have come out of the push to exascale?

I think an under-rated success story of the ECP has been the way the technical advances made to the DOE’s scientific software stack have had spin-off benefits for smaller-scale scientific computing. The exascale-driven push towards GPU computing has benefited AMReX users who have no intention of ever running on a large fraction of Perlmutter or Summit. A number of academic groups contact us wanting to re-factor their existing simulation codes to use AMReX, both for its ability to support adaptive mesh refinement and for its performance portability across architectures. More locally, this past summer two undergraduate interns, Amanda Harkleroad and Emily Bogle, working with recent UC Berkeley graduate Victor Zendejas Lopez, helped build an AMReX-based code to model the growth of cancer cells. Due to improvements made to AMReX as part of the ECP, they can write code once and it will run on both commodity CPU and GPU hardware. I think that’s pretty cool.




Soren Prestemon Elected as APS Fellow

Soren Prestemon

Soren Prestemon. Credit: Berkeley Lab/Paul Mueller

Soren Prestemon, ATAP’s Deputy Division Director for Technology, has been elected a Fellow of the American Physical Society.

He was nominated by the APS Division of Physics of Beams “for multiple, significant contributions to the research and development of high performance resistive, permanent magnet, and superconducting magnet systems for science applications from light-sources to high-energy physics.”

Prestemon heads our Superconducting Magnet Program. He also serves as Director of the multi-institutional U.S. Magnet Development Program and of the ATAP-Engineering Division Berkeley Center for Magnet Technology.

“I appreciate Soren’s leadership over many years in the Laboratory and community, establishing advanced magnets as a key driver of future HEP capabilities and also of the FES long range plan for fusion,” said ATAP Division Director Cameron Geddes.

Prestemon is the 30th member of ATAP and its predecessor organizations to receive this honor.

He is one of five Berkeley Lab researchers elected to APS Fellowship this year. Wanli Yang of the Advanced Light Source was also honored, and Naomi Ginsberg, Lane Martin, and Kristin Persson were nominated through UC-Berkeley. The honor recognizes exceptional contributions to the physics enterprise.



Chad Mitchell Receives Berkeley Lab Director’s Award

Chad Mitchell

Chad Mitchell

Chad Mitchell, a staff scientist in ATAP’s Accelerator Modeling Program, was presented the Berkeley Lab Director’s Award in the category of Scientific Achievement in a virtual ceremony November 18, 2021.

He leads a team that developed novel beam dynamics methods to significantly extend the reach of future intensity-frontier particle accelerators for high energy physics discovery science, as well as for practical applications of high-intensity (multi-megawatt) proton beams.

A Zoom recording of the awards ceremony is available online (Berkeley Lab login credentials required); Mitchell is presented with the award by Natalie Roe, Associate Laboratory Director for Physical Sciences, beginning at 54:36.




Get Outside! And Other Tips to Stay Healthy and Well

Sunset over Golden Gate Bridge

Working late? Why not make time for a sunset. (Photo courtesy Asmita Patel)

The Lab’s Bay Area location includes an unparalleled abundance and variety of outdoor recreation opportunities. Even spending some time in your front yard or at a neighborhood park can be great for your physical health and your state of mind.

Suggestions for this and much more can be found on a new website, “Healthy and Well at LBNL.” Three Berkeley Lab organizations — the Health Services Group, the Human Resources Division, and the Inclusion, Diversity, Equity, and Accountability (IDEA) Office — have joined forces to bring us tips, links, and pointers to resources on physical well-being, work-life balance, and much more.



A Season for Sharing through the Food Bank Challenge

Bag of apples from food bank

Sharing our good fortune

With Federal pandemic benefits expired and the cost of living on the rise, food banks in our area have seen a remarkable rise in already-high demand. We can help.

Through Friday, January 7, Berkeley Lab is holding the 2021 Winter Food Bank Challenge, benefitting the Alameda County Community Food Bank and the Food Bank of Contra Costa and Solano Counties. To inspire a little friendly competition, the Lab is organized into six teams. The Physical Sciences Area, which includes ATAP, is teamed up with the Projects and Infrastructure Modernization Division.

You can help the less fortunate by donating to either or both of these food banks through our team’s links by January 7, or by volunteering at those food banks and reporting your time. Visit the 2021 Winter Food Bank Challenge website for more information. Let’s beat last year’s $135,000 total



Lactation Accommodations

Standard breastfeeding icon

A room is available on request in B71

Berkeley Lab recently rolled out a new policy on lactation accommodations. It was drafted by Human Resources and improved based on feedback from the Lab’s Women Scientists and Engineers Council (WSEC) policy subcommittee.

A number of dedicated lactation rooms at the Lab can be reserved through Google Calendar. All these official lactation rooms are equipped with a hospital-grade pump. For more information (and a site with a great deal of other helpful information for parents), visit

In Building 71, we will make arrangements for an office as an unofficial lactation room. To obtain a key and directions, please contact ATAP Division Administrator Wes Tabler or Outreach/IDEA coordinator Ina Reichel. We will provide door hanger signs to show that the assigned office is in use for this purpose.




CDC collage of people with disabilities

Our communication choices can help make the 60 million adult Americans who report having one or more disabiities feel respected and included. (Illustration courtesy CDC)


Our choice of words, and of the ideas we express with them, can either uplift others or cause hurt and reinforce stereotypes. Disability, a widespread aspect of the human condition, is no exception to this principle. The Centers for Disease Control and Prevention have developed guidelines for understanding, dignity, and respect when Communicating With and About People with Disabilities.

Key takeaways

•   People-first language is the best place to start when talking to or about a person with a disability.
•   If you are unsure, ask the person how they would like to be described.
•   It is important to remember that preferences can vary.





Advanced Light Source Accelerator Physics

M. Ehrlichman, T. Hellert, S.C. Leemann, G. Penn, C. Steier, C. Sun, M. Venturini, and D. Wang, “Three-dipole kicker injection scheme for the Advanced Light Source upgrade accumulator ring,” accepted by Physical Review Accelerators and Beams, preprint online 29 November 2021.

Accelerator Modeling Program

Olga Shapoval, Remi Lehe, Maxence Thévenet, Edoardo Zoni, Yinjian Zhao, and Jean-Luc Vay, “Overcoming timestep limitations in boosted-frame particle-in-cell simulations of plasma-based acceleration”, Physical Review E 104, 055311 (29 November 2021),

D. A. Bizzozero, J. Qiang (LBNL); L. Ge, Z. Li, C. Ng, L. Xiao (SLAC), “Multi-objective optimization with an integrated electromagnetics and beam dynamics workflow,” Nuclear Instruments & Methods in Physics Research A 1020, 165844 (21 December 2021),

J.-L. Vay, A. Huebl, R.Lehe (LBNL); N.M. Cook (RadiaSoft LLC); R.J. England (SLAC); U. Niedermayer (TU Darmstadt); P. Piot (Northern Illinois University and ANL); F. Tsung (UCLA); D. Winklehner (MIT), “Modeling of Advanced Accelerator Concepts,” ICFA Beam Dynamics Newsletter, Journal of Instrumentation 16, T10003 (11 October 2021),

D. Sagan (Cornell University); M. Berz (Michigan State University); N.M. Cook (RadiaSoft LLC); Y. Hao (BNL); G. Hoffstaetter (Cornell University); A. Huebl (LBNL); C.-K. Huang (LANL); M.H. Langston (Reservoir Labs Inc.), C.E. Mayes (SLAC); C.E. Mitchell (LBNL); C.-K. Ng (SLAC); J. Qiang, R.D. Ryne (LBNL); A. Scheinker (LANL); E. Stern (FNAL); J.-L. Vay (LBNL); D. Winklehner (MIT); H. Zhang (TJNAF); “Simulations of Future Particle Accelerators: Issues and Mitigations”, ICFA Beam Dynamics Newsletter, Journal of Instrumentation 16, T10002 (11 October 2021),

A. Myers, A. Almgren, L. D. Amorim, J. Bell (LBNL); L. Fedeli (CEA Saclay); L. Ge (SLAC and LBNL); K. Gott (LBNL); D.P. Grote (LLNL); M. Hogan (SLAC); A. Huebl, R. Jambunathan, R. Lehe (LBNL); C. Ng (SLAC); M. Rowan, O. Shapoval (LBNL); M. Thévenet (DESY); J.-L. Vay (LBNL); H. Vincenti (CEA Saclay); E. Yang (LBNL); N. Zaim (CEA Saclay); W. Zhang, Y. Zhao and E. Zoni (LBNL), “Porting WarpX to GPU-accelerated platforms”, Parallel Computing 108, 102833 (14 September 2021)

Lipeng Wan (ORNL); Axel Huebl, Junmin Gu (LBNL); Franz Poeschel, CAUSUS);
Ana Gainaru, Ruonan Wang, Jieyang Chen (ORNL); Xin Liang (Missouri University of Science and Technology); Dmitry Ganyushin (ORNL); Todd Munson, Ian Foster (ANL); Jean-Luc Vay (LBNL); Norbert Podhorszki (ORNL); Kesheng Wu (LBNL); Scott Klasky (ORNL), “Improving I/O Performance for Exascale Applications through Online Data Layout Reorganization,” IEEE Transactions on Parallel & Distributed Systems 33, 878-890 (April 2022), early access (December 2021),

L. Fedeli, A. Sainte-Marie, N. Zaim (CEA Saclay); M. Thévenet (LBNL, now DESY); J.L. Vay, A. Myers (LBNL); F. Quéré, and H. Vincenti (CEA Saclay), “Probing strong-field QED with Doppler-boosted petawatt-class lasers”, Physical Review Letters 127, 114801 (10 September 2021,)

Invited talks without publication opportunity

A. Huebl, “Computational Frontier Status”, 2021 AF1 Community Meeting, Nov. 22-23, 2021.

J. Qiang, “Envelope instabilities and their mitigation in high intensity hadron beams” 64th ICFA beam dynamics workshop on High Intensity and High Brightness Hadron Beams, Fermilab, Chicago, Oct. 3-8, 2021.

A. Huebl, “openPMD – Scientific, Community Meta-Data Standard”, Workshop on SAXS@XFELs and HI & HE laser driven matter, Nov 4-5, Dresden, Germany.

BELLA Center

D.P. Grote, A. Friedman, C.G.R. Geddes, R. Lehe, C. Benedetti, T. M. Ostermayr, H-E Tsai, J.-L. Vay, C.B. Schroeder, E. Esarey, “Reduced bandwidth Compton photons from a laser-plasma accelerator using tailored plasma channels,” Physics of Plasmas (accepted).

A. Zingale, N. Czapla, D.M. Nasir (The Ohio State University); S.K. Barber, J.H. Bin, A.J. Gonsalves, F. Isono, J. van Tilborg, S. Steinke, K. Nakamura (LBNL); G.E. Cochran (LLNL); J. Purcell (The Ohio State University); W.P. Leemans (LBNL, now at DESY); C.G.R. Geddes, C.B. Schroeder, E. Esarey (LBNL); D.W. Schumacher (The Ohio State University), “Emittance preserving thin film plasma mirrors for GeV scale laser plasma accelerators,” Physical Review Accelerators and Beams 24, 121301 (2 December 2021);





Safety Week Awards Honor Top Performers

The success of Physical Sciences Area Safety Week is built on an all-hands effort, but each year, some stand out for exceptional dedication and the quality of their contributions.To promote ongoing safety-culture awareness and maintain the momentum of Safety Week, we honor an outstanding individual worker and the top-performing self-assessment team for outstanding safety and organization effort.

Individual Award: Wes Tabler

Wes Tabler

Wes Tabler

Individual Award certificate

“Most helpful to others”

ATAP Division Administrator Wes Tabler received the individual award, honoring the person most helpful to others in Safety Week efforts. He went the extra mile in contributions throughout the entire Safety Week cycle, from helping make logistics arrangements and assignments beforehand, through ensuring good stewardship of tagged property during the event, to helping with follow-up on the matters that required additional planning and resources.

Team Award: HL-LHC AUP

Team Award certificateTeam honors go to the assessment team for the High-Luminosity LHC Accelerator Upgrade Project for their performance in work-area cleanup and assessment and their commitment to workplace safety. Their task involved Building 77A, where a wide variety of magnet structure and assembly and cable winding tasks are underway. They were selected for this honor by division management, after final walkthroughs and reports from all the teams. Team members included Ahmet Pekedis, Al Baskys, Andy Lin, Carlos Perez, Elizabeth Lee, Josh Herrera, Katherine Ray, Matt Reynolds, Juan Rodriguez, Mike Naus, and Mike Solis, led by Dan Cheng and Ian Pong.

Montage of individual pictures of the HiLumi-LHC Safety Week team

Team members included Ahmet Pekedis, Al Baskys, Andy Lin, Carlos Perez, Elizabeth Lee, Josh Herrera, Katherine Ray, Matt Reynolds, Juan Rodriguez, Mike Naus, and Mike Solis, led by Dan Cheng and Ian Pong.

These honors were the result of pleasantly difficult decisions in assessing the excellent contributions of so many people across the Division. Let’s maintain the momentum on Safety Week’s themes of clean and well-organized workspaces, diligent chemical stewardship, and up-to-date training, and have another year of doing great science safely.


Safety Week Photostory

The Physical Sciences Area held Safety Week September 27 – October 1, 2021. The popular tradition began as Safety Day, an ATAP initiative spearheaded by Deputy Division Director Asmita Patel and Safety Coordinator Pat Thomas. The Engineering Division soon joined with us, and the Physics Division and the ALS-U Project followed suit.

Cameron Geddes in a screen shot of Safety Week
Asmita Patel on Safety Week Zoom call
Goat grazing is one of the Lab's favorite wildfire prevention methods

To see more highlights, visit our Safety Week photostory.



Integrated Safety Management and the Hidden Dangers of Quotidian Risks

Integrated Safety Management Circle of Safety infographic

The circle of safety

“ISM 101,” a 20-minute online course, was developed by the Engineering Division to help us all understand the core principles of Integrated Safety Management (ISM) and how its five steps help ensure our own safety — and the safety of those around us.

The course emphasizes the normalized risks that hide beneath a cloak of familiarity and complacency in routine work, and how the principles of ISM apply to everything we do. It is a good refresher for everyone and especially recommended for those new to the Lab.



Putting Out the Unwelcome Mat for Four- and Six-Legged Holiday Guests

mouse climbing some computer wiresAt this time of year, mice and rats often try to come indoors. Rodents can leave messes and spread diseases… and they are notorious for gnawing on electrical wiring. Ants, too, can invade over the holidays; interior and upper-storey offices are not safe. Here are some tips on how to be a less inviting holiday host as we leave the Lab for the year-end shutdown.
 • Keep nonperishable snack foods and earthquake supplies in a closed container they cannot easily gnaw though, not loose in a desk drawer or backpack.
 • Remove any food items at the end of each day, and be sure that your under-desk trash can (if you use one) is free of food scraps.
 • Don’t leave perishables in breakroom refrigerators during the break. Bacteria and mold won’t be taking a holiday!
 • Wipe down desktops, tables, and counter tops after food has been consumed. Mere scraps and crumbs by our standards can be a feast for something the size of a mouse, never mind an ant.
 • Be sure that the last of the trash bags go to outside dumpsters before a building is left unoccupied over the break.

If you do see rodents or other pests, contact your Building Manager or the Work Request Center to request Pest Control services.

Do not attempt to clean up dead rodents or droppings. Contact your custodians. They are trained in how to clean up safely.



Let’s Think On Our Feet This Winter

Slips, trips, and falls prevention poster

Don’t let a happy holiday slip away! Movie courtesy Horst Simon, emeritus LBNL Deputy Director for Research, and Sponsor, Berkeley Lab Safety Culture Work Group. Poster by Lucky Cortez, UCSF, formerly of the ATAP Operations Team.

As we approach the longest night of the year here in the Northern Hemisphere, with rain often in the picture, leaves on the sidewalks and stairways, and holiday decorations almost within easy reach, this is a crucial time for slip, trip, and fall prevention both at the Lab and at home.

Let’s walk (and drive and bike) mindfully, which includes paying attention to the physical world around us rather than the virtual world in handheld devices.

Use handrails on stairways and steep walkways, and clean up slippery spills before others come upon them unawares.

Using ladders properly is important at any time of year. For more information on safe use of ladders and stepstools, contact Alyssa Brand, ext. 7246.

Further tips to keep easily prevented accidents from spoiling the festivities are available from the National Safety Council and the US Fire Administration.

Here’s wishing you and yours a happy holiday season and a safe return in the new year!



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Director’s Corner

Cameron Geddes, ATAP Division Director

Teamwork and collaboration are common themes of the achievements that we report this month. The BELLA Center has published experimental results that show excellent quality and reproducibility in plasma lensing and transport of laser pulses within long capillaries. The results are a vote of confidence in the technology base for scaling up laser-plasma accelerators to higher energies. Marlene Turner, one of the many strong postdoctoral scholars throughout ATAP, played a key role in the R&D team and is lead author of the paper in the Oxford University Press journal High Power Laser Science and Technology.

A collaboration led by CEA, with strong participation by our Accelerator Modeling Program, has published a Physical Review Letter showing how high-power lasers and plasma mirrors can be combined into a new way of experimentally probing strong-field quantum electrodynamics. It is a remarkable demonstration of the power of simulation and modeling as tools of discovery, and a fine example of team science — a bedrock attribute of Berkeley Lab, often reaching across institutional and even international borders.

ATAP’s researchers have been recognized with several honors recently. Chad Mitchell of the Accelerator Modeling Program won the Berkeley Lab Director’s Award for Scientific Achievement. Simon Leemann, Yuping Lu, Hiroshi Nishimura, and Changchun Sun were members of a multi-divisional team honored with the Klaus Halbach Award for Innovative Instrumentation by the Advanced Light Source for their work on applying machine learning to improve beam stability and thus performance at that facility. Arun Persaud of the Fusion Science & Ion Beam Technology Program received the Outstanding Mentor Award from the Lab’s Workforce Development & Education Office.

Working safely is a fundamental requirement of doing business throughout Berkeley Lab, and as September draws to a close, the Physical Sciences Area is holding Safety Week — the traditional Safety Day distributed across a workweek in the name of social distancing. A special feature this year is a series of midday seminars, including a seminar on Inclusion, Diversity, Equity, and Accountability (IDEA)—which we can think of as adding psychological safety to our traditional emphasis on physical safety.

Speaking of safety, October will bring the anniversary of both the Loma Prieta earthquake in 1989 and the Oakland/Berkeley Hills conflagration of 1991. It’s a good reminder of the importance of planning and some simple physical preparation in surviving and recovering when (not if) another such crisis affects the Bay Area.



—Important confirmation that scale-up will work

A 20-centimeter-long capillary discharge waveguide, used at BELLA Center to guide high-intensity laser pulses, and applied to set their record thus far for accelerating electrons: 8 billion electron volts (GeV). (Credit: Thor Swift/Berkeley Lab)

High-power laser pulses focused to small spots to reach incredible intensities enable a variety of applications, ranging from scientific research to industry and medicine. At the Berkeley Lab Laser Accelerator (BELLA) Center, for instance, intensity is key to building particle accelerators thousands of times shorter than conventional ones that reach the same energy. However, laser-plasma accelerators (LPAs) require sustained intensity over many centimeters, not just a spot focus that rapidly expands because of diffraction.

To achieve sustained intensity, the BELLA Center, at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), uses thin hollow structures, or “capillaries,” containing a plasma to transport the pulses of light. BELLA Center scientists have been pushing toward longer and longer capillaries as they strive for higher beam energies with their LPAs.

Their latest work shows, with higher precision than ever before, that these plasma waveguides are extremely stable and of reproducibly high quality, and that these characteristics can be maintained over distances as long as 40 centimeters. It confirms that this key technology for LPAs can be scaled up as the BELLA Center pushes toward higher energies, benefitting potential applications that range from biomedical research and treatment to free-electron-laser light sources for research facilities.

The work – led by postdoctoral scholar Marlene Turner, working with staff scientist Anthony Gonsalves – is described in a study published in the journal High Power Laser Science and Engineering.

More …

“This work shows that capillaries can produce extremely stable plasma targets for acceleration, indicating that observed variations in accelerator performance are likely primarily laser fluctuation driven, which indicates the need for active laser feedback control,” said Cameron Geddes, director of the Accelerator Technology and Applied Physics Division, parent organization of the BELLA Center.

Plasma channels give consistent guidance to powerful pulses

Fiber optics can transport laser beam pulses over thousands of kilometers, a principle familiar in modern computer networks. However, with the high laser intensities used at BELLA Center (20 orders of magnitude more intense than the sunlight on the Earth’s surface), electrons would be near-instantaneously removed from their parent atoms by the laser field, destroying solid materials such as glass fibers. The solution is to use plasma, a state of matter in which electrons have already been removed from their atoms, as a “fiber.”

Marlene Turner (right) collaborating under COVID precautions with Anthony Gonsalves. (Credit: Thor Swift/Berkeley Lab)

The BELLA Center has used plasmas to guide laser pulses over distances as long as 20 centimeters to achieve the highest laser-driven particle energies to date. The plasma is created by an electrical discharge inside the capillary. This is where electrons “surf” a wave of ultrahigh electric field set up by the laser pulse. The longer the sustained focus, the faster they are going at the end of the ride.

However, the gas breakdown in an electrical discharge is a violent and largely uncontrolled event (imagine a tiny, confined lightning strike). Charting a path forward to ever higher energies and precision control at the BELLA Center, researchers needed to know how reproducible the wave-guiding characteristics are from one laser pulse to another, and how well each laser pulse can be guided.

In order to give wave-guiding results analogous to a fiber optic, the plasma density should be lowest in the center, with a profile mathematically described as parabolic. “We showed, with unprecedented precision, that the plasma profiles are indeed very parabolic over the laser pulse spot size they are designed to guide,” said Gonsalves. “This allows for pulse propagation in the waveguide without quality degradation.”

Other types of plasma waveguides (there are several ways to create them) can also be measured with high precision using these methods.

The measurement precision was also ideal for investigating how much the density profile changes from one laser shot to another, since although the capillary is durable, the wave-guiding plasma within it is formed anew each time. The team found outstanding stability and reproducibility.

“These results, along with our ongoing work on active feedback aided by machine learning techniques, are a big step to improving the stability and usability of laser-plasma accelerators,” said Eric Esarey, director of the BELLA Center. (Active feedback to stabilize laser fluctuations is also the subject of research and development at the BELLA Center.)

Guided laser pulses illuminate a path toward progress

Laser-plasma acceleration technology could reduce the size and cost of particle accelerators –increasing their availability for hospitals and universities, for instance, and ultimately bringing these benefits to a next-generation particle collider for high-energy physics. One of the keys to increasing their particle-beam energy beyond the present record of 8 billion electron volts (GeV) is the use of longer accelerating channels; another is “staging,” or the use of the output of one acceleration module as the input to another. Verifying the quality of the plasma channel where the acceleration takes place — and the consistency and reproducibility of that quality — gives a vote of confidence in the technology basis of these plans.

Marlene Turner inspects a 40-centimeter-long capillary. (Credit: Thor Swift/Berkeley Lab)

Aside from showing that this capillary-based waveguide is of high and consistent quality, this work involved waveguides twice as long as the one used for achieving record-breaking energy. “The precision 40-centimeter-long waveguides we have now developed could push those energies even higher,” said Turner.

The work was supported by the DOE Office of Science, Office of High Energy Physics.

To learn more…

Marlene Turner et al., “Radial density profile and stability of capillary discharge plasma waveguides of lengths up to 40 cm,” High Power Laser Science and Engineering 9, e17 (26 April 2021).




— Berkeley Lab’s researchers, unique capabilities aided international effort to probe fundamental questions in physics
By William Schulz

The successive interaction of a high-power laser pulse (red and blue) with a plasma mirror (not shown) and a secondary target (translucent light grey) could create the conditions to probe Strong Field Quantum Electrodynamics effects that are far beyond current experimental capabilities. (Credit: Luca Fedeli/CEA).

A newly published theoretical and computer modeling study suggests that the world’s most powerful lasers might finally crack the elusive physics behind some of the most extreme phenomena in the universe – gamma ray bursts, pulsar magnetospheres, and more.

The international research team behind the study includes researchers from Lawrence Berkeley National Laboratory (Berkeley Lab) and France’s Alternative Energies and Atomic Energy Commission (CEA-LIDYL). They report their findings in the prestigious journal Physical Review Letters.

“A powerful demonstration of how advanced simulation of complex systems can enable new paths for discovery.”
— ATAP Division Director Cameron Geddes

The research team was led by CEA’s Henri Vincenti, who proposed the main physical concept. Jean-Luc Vay and Andrew Myers, of Berkeley Lab’s Accelerator Technology and Applied Physics (ATAP) Division and Computational Research Division, respectively, led development of the simulation code used for the research. (Vincenti previously worked at Berkeley Lab as a Marie Curie Research Fellow and remains an ATAP affiliate and frequent collaborator.) The theoretical and numerical work was led by Luca Fedeli from Vincenti’s team at CEA.

The team’s modeling study shows that petawatt (PW)-class lasers – juiced to even higher intensities via light-matter interactions – might provide a key to unlock the mysteries of the strong-field (SF) regime of quantum electrodynamics (QED). A petawatt is 1 times ten to the fifteenth power (that is, followed by 15 zeroes), or a quadrillion watts. The output of today’s most powerful lasers is measured in petawatts.

“This is a powerful demonstration of how advanced simulation of complex systems can enable new paths for discovery science by integrating multiple physics processes – in this case, the laser interaction with a target and subsequent production of particles in a second target,” said ATAP Division Director Cameron Geddes.

Lasers probe some of nature’s most jealously guarded secrets

More …

While QED is a cornerstone of modern physics that has withstood the rigor of experiment over many decades, probing SF-QED requires electromagnetic fields of an intensity many orders of magnitude beyond those normally available on Earth.

Researchers have tried side routes to SF-QED, such as using powerful particle beams from accelerators to observe particle interactions with the strong fields that are naturally present in some aligned crystals.

For a more direct approach, the highest electromagnetic fields available in a laboratory are delivered by PW-class lasers. A 10-PW laser (the world’s most powerful at this time), focused down to a few microns, can reach intensities close to 1023 watts per square centimeter. The associated electric field values can be as high as 1014volts per meter. Yet studying SF-QED requires even higher field amplitudes than that – orders of magnitude beyond what can be achieved with those lasers.

To break this barrier, researchers have planned to call on powerful electron beams, accessible at large accelerator or laser facilities. When a high-power laser pulse collides with a relativistic electron beam, the laser field amplitude seen by electrons in their rest frame can be increased by orders of magnitude, giving access to new SF-QED regimes.

Though such methods are challenging experimentally, as they call for the synchronization in space and time of a high-power laser pulse and a relativistic electron beam at femtosecond and micron scales, a few such experiments have been successfully conducted, and several more are planned around the world at PW-class laser facilities.

Using a moving, curved plasma mirror for a direct look

The research team proposed a complementary method: a compact scheme that can directly boost the intensity of existing high-power laser beams. It is based on a well-known concept of light intensification and on their theoretical and computer modeling studies.

The scheme consists of boosting the intensity of a PW laser pulse with a relativistic plasma mirror. Such a mirror can be formed when an ultrahigh intensity laser beam hits an optically polished solid target. Due to the high laser amplitude, the solid target is fully ionized, forming a dense plasma that reflects the incident light. At the same time the reflecting surface is actually moved by the intense laser field. As a result of that motion, part of the reflected laser pulse is temporally compressed and converted to a shorter wavelength by the Doppler effect.

Radiation pressure from the laser gives this plasma mirror a natural curvature. This focuses the Doppler-boosted beam to much smaller spots, which can lead to extreme intensity gains – more than three orders of magnitude – where the Doppler-boosted laser beam is focused. The simulations indicate that a secondary target at this focus would give clear SF-QED signatures in actual experiments.

Strongfield QED probe explanation

Left: In the proposed scheme for probing SF-QED with present-day or near-future lasers, a plasma mirror shaped by radiation pressure converts an intense laser pulse (red) into Doppler-boosted harmonics (purple) and focuses them on a secondary target, reaching extreme intensities. The dimensions involved are tens to hundreds of microns (millionths of a meter); the diameter of a human hair is a few to several tens of microns. (Credit: Luca Fedeli/CEA)
Right: Berkeley Lab’s key contribution was leading the development of the simulation code used for the research. In this simulation image, the intense Doppler-boosted light pulses (red and blue) plow through the solid target (gray), generating high-energy photons (orange) that decay into pairs of electrons (green) and positrons (purple) after further interaction with the incoming light pulses. The electrons and positrons are separated due to the strong laser field. Only photons that have not yet decayed into pairs are shown. (Credit: Luca Fedeli/CEA)


Berkeley Lab integral to international team-science effort

The study drew upon Berkeley Lab’s diverse scientific resources, including its WarpX simulation code, which was developed for modeling advanced particle accelerators under the auspices of the U.S. Department of Energy’s Exascale Computing Project. The novel capabilities of WarpX allowed the modeling of the intensity boost and the interaction of the boosted pulse with the target. All previous simulation studies had only been able to explore proof-of-principle configurations.

Experimental verification of the research team’s methodology for probing SF-QED might come from the Berkeley Lab Laser Accelerator (BELLA), a petawatt-class laser with a repetition rate, unprecedented at that power, of a pulse per second. Now under construction is a second beamline that might also contribute to experimental studies of SF-QED by Berkeley Lab researchers. A proposed new laser, kBELLA, could enable future high rate studies by bringing high intensity at a kilohertz repetition rate to the facility.

The discovery via WarpX of novel high-intensity laser-plasma interaction regimes could have benefits far beyond ideas for exploring SF-QED. These include the better understanding and design of plasma-based accelerators such as those being developed at BELLA. More compact and less expensive than conventional accelerators of similar energy, they could eventually be game-changers in applications that range from extending the reach of high-energy physics and of penetrating photon sources for precision imaging, to implanting ions in semiconductors, treating cancer, developing new pharmaceuticals, and more.

“It is gratifying to be able to contribute to the validation of new, potentially very impactful ideas via the use of our novel algorithms and codes,” Vay said of the Berkeley Lab team’s contributions to the study. “This is part of the beauty of collaborative team science.”

This work was supported by the French National Research Agency (ANR) T-ERC program, the European Union’s Horizon 2020 research and innovation program, and the Cross-Disciplinary Program on Numerical Simulation of CEA, the French Alternative Energies and Atomic Energy Commission. Berkeley Lab’s participation was supported by the Exascale Computing Project, a collaborative effort of DOE’s Office of Science and National Nuclear Security Administration. The simulations were run on the Summit supercomputer at Oak Ridge National Laboratory, using computer time awarded to “Plasma Mirrors ‘in Silico’: Extreme Intensity Light Sources and Compact Particle Accelerators” by the Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program.

To Learn More…

Reaching Remarkable States of Matter with Laser Simulations,” by Rachel McDowell, Oak Ridge Leadership Computing Facility.

L. Fideli et al., “Probing Strong-Field QED with Doppler-Boosted Petawatt-Class Lasers,” Physical Review Letters 127, 114801 (10 September 2021).





— Finale of Lab’s 90th Anniversary celebrations

The Laboratory has been celebrating its 90th anniversary throughout 2021. In a very real sense, this is ATAP’s 90th anniversary as well. The Division carries forward E.O. Lawrence’s two great contributions to the world of science: advanced particle accelerators and the “team science” approach to designing, building, and operating them.

As the finale of the Laboratory’s Next 90 series, Berkeley Lab Strategic Communications focused on this founding legacy of Lawrence and his laboratory. We welcome you to look at accelerator breakthroughs of the past 90 years and a glimpse of what the next 90 might hold, and get perspective from conversations with ATAP Director Cameron Geddes and early-career scientist Antoine Wojdyla.

Photostory: Particle Accelerators at Berkeley Lab

Credit: Joe Chew/Berkeley Lab

The first version of E.O. Lawrence’s invention could fit in the palm of your hand, but this tiny thing would go on to change the world.

Ninety years after the invention of the cyclotron, accelerators of many kinds are a vital part of many disciplines of modern science and are used in industry and medicine as well. Learn more in Particle Accelerators at Berkeley Lab: Writing The Next Chapters of a 90-Year Story.

Video: Excellence in Accelerators

Watch as E.O. Lawrence’s original sketch on a paper napkin evolves into the many types of accelerators in use around the world today. This companion article goes into more detail. Credit: Video by Marilyn Chung of the Berkeley Lab Creative Services Office, with writing and production assistance by Glenn Roberts, Jr., of Berkeley Lab Strategic Communications, and Asmita Patel and Joe Chew, ATAP. Originally published October 2019.

90th Anniversary Accelerator Week: A Conversation with Cameron Geddes

Cameron Geddes

Cameron Geddes

Scientists in the Accelerator Technology and Applied Physics (ATAP) Division, part of the Lab’s Physical Sciences Area, support the DOE and Laboratory missions by inventing, developing, and deploying particle accelerators, adjacent technologies including fusion energy, and photon sources to explore and control matter and energy. Often associated with their origins in particle physics, accelerators have become vital infrastructure throughout modern science, and have many industrial, medical, and national-security applications as well. ATAP Division Director Cameron Geddes discusses how they design and build these engines of discovery and the exciting future prospects for this founding legacy of the Laboratory.

More …

How do the Lab’s accelerators support the Lab’s mission?
The Laboratory’s leadership in these areas is based on the twin central legacies of E.O. Lawrence. One is the accelerators themselves; he of course invented the cyclotrons that started modern accelerator science. His other legacy—comparable to particle accelerators in its revolutionary nature and breadth of influence—is team science, which is foundational to our own workstyle and our numerous intramural and extramural partnerships, and is fundamentally necessary for the scale of much of the research we perform today. We invite you to watch the Berkeley Lab video Excellence in Accelerators to learn more about what we do, why, and how.

Particle accelerators and accelerator-based photon sources are indispensable engines of scientific discovery and are used in applications across industry, national security, and medicine. Here at Berkeley Lab, the Advanced Light Source (ALS) is a shining example. It accelerates electrons and uses precise control of electron beams to create soft x-rays to probe matter. Thousands of users a year explore materials, improve batteries, advance biosciences, and more with these x-ray beams. We are also extensively involved in designing the next-generation version of this user facility, the ALS Upgrade.

Extending the capabilities and reducing the size and cost of accelerators hold the key to several grand challenges of science, including better understanding the structure of the universe through high energy particle physics; creating brilliant photon sources for basic energy sciences and materials; and exploring new states of matter. These and related systems are also crucial to fusion energy sciences. ATAP is driving the extension of existing particle accelerators using advanced magnets, controls, simulations, and beam physics. For example, new high-field magnets are being used to upgrade the Large Hadron Collider in its search for new particles, as well as in compact fusion-energy concepts.

At the same time, we are creating new compact accelerator technologies and the lasers that drive them, with the potential to greatly extend the reach of fundamental science and also to make the advanced capabilities developed in leading-edge large scientific facilities such as the Advanced Light Source available to applications from medicine to security. For example, advanced laser-driven accelerators may form the basis for the next generation of very high-energy colliders. In addition, making high-performance accelerators compact enough to fit in a clinic or factory could support improved cancer detection and treatment, precision nondestructive measurements required for advanced manufacturing and nuclear security, and environmental carbon sensing for understanding global climate.

What are the top 3 or 4 areas of interest or areas of growth for the accelerators today?
The top drivers for the next generation of accelerators include: enabling new advances in fundamental physics; advancing medical and security measurements and treatments; creating clean fusion energy; and enabling tools for a carbon economy and quantum information science. Developing the required performance requires drawing on a wide variety of technologies and areas of scientific research. The Laboratory is uniquely positioned to do this through our interlinked programs in superconducting magnets and advanced precision controls that are the key to next-generation accelerators and fusion devices, laser-driven particle accelerators that offer transformative compactness and the lasers that drive them, accelerator physics for light sources (including ALS and ALS-U) and particle colliders, and accelerator and fusion applications. Computing is a vital tool throughout, and we both use and advance the state of the art in high-performance simulations and tools leading the push toward the exascale, and apply artificial intelligence and machine learning feedback concepts that enable understanding and control of the complexity required for high performance. Key directions include:

•  Extending the capabilities of accelerators for high energy particle physics at the energy and intensity frontiers, as well as next-generation photon sources. New high strength magnets are extending the reach of discovery at machines like the Large Hadron Collider that probe fundamental particle physics and expand our understanding of the basic physical laws that are at the root of the physical sciences. Feedback controls (including AI/ML) and advanced simulations allow us to better understand and control complex systems, extending performance both for photon sources like ALS-U and for colliders.

•  Pioneering a new generation of radically more compact accelerators, which achieve in centimeters what takes current technologies hundreds of meters. Using intense lasers to drive waves in ionized plasma, we circumvent the limits on how much acceleration present-day machines, based on radiofrequency power in resonant metallic cavities, can impart to particles. This has the potential to enable much higher energy systems at a physically and financially practical size, extending the reach of basic science in understanding fundamental physical laws and the structure of the universe through high-energy particle physics. These fundamental interactions are at the heart of physics and the physical sciences. En route to this long-term goal of a collider, this line of research could enable a new generation of laboratory-scale free-electron lasers and other photon sources.

•  Creating capabilities to bring the power of Berkeley Lab science to the world. To take a few examples: A compact neutron source and detector system could enable sensing of the amount and distribution of carbon in the soil, a key to moving toward a low-carbon economy to protect the global climate. Compact charged particle sources are being used to research new methods of radiotherapy for cancer treatment. Compact accelerators creating precision photon sources allow X-ray images to be taken with much greater resolution and reduced radiation dose, improving medical screening and security applications. High field magnets would make a potential fusion energy source more compact and affordable. And high-intensity beams create new states of matter, including unique ways to form qubits for quantum information science.

•  Building a new generation of lasers that combine high average power and high peak power in short pulses. Nearly-continuous lasers have already transformed many industrial processes, such as welding, by delivering kilowatts of average power with precision. Short-pulse lasers, lasting less than a trillionth of a second but with peak powers of hundreds of trillions of watts, unlock new physics interactions, including the keys to new laser-driven accelerators, tailoring material surfaces to create hydrophobicity or other properties, and more. We are pioneering the coherent combination of many ultrafast fiber lasers to create the short pulses at high repetition rates and average powers that are required for these and other applications.

These endeavors are made possible by our people. ATAP emphasizes mentorship to develop the national scientific workforce and educate the next generation – from students and postdoctoral researchers to career staff. ATAP’s strong divisional operations team is key to our success with complex projects, multi-agency engagement, and collaboration across the Laboratory. We place great emphasis on the Lab’s IDEA goals, including an active IDEA committee and participation in employee resource groups (I am an active member of the Lambda Alliance Employee Resource Group). We want ATAP to be a place where everyone feels that they are valued and that they can reach their full potential—a place where we don’t just accept differences, but celebrate them, which improves both the work environment and the results.

Who do you partner with at the Lab to be successful?
Because accelerators are essential tools across the sciences and for society, we partner broadly across the Laboratory. To give just a few examples, we are conducting experiments with the BioSciences Area on how the short pulses of ions produced by new plasma accelerators could improve cancer therapy. Together with the Nuclear Science Division, we are developing and testing sources of mono-energetic X-rays that could revolutionize sensitivity and reduce the radiation dose required for imaging needs across medicine, security, and industry. We partner with the Physics Division on combinations of accelerators and detectors that will advance our understanding of the structure of the universe through high energy particle physics. We create computer simulation codes and methods to understand and control complex systems in coordination with Computing Sciences and NERSC. We support Advanced Light Source operations and the Advanced Light Source Upgrade project with beam physics, diagnostics, and controls that push the facility beyond the state of the art; the result benefits soft-x-ray users throughout the physical and life sciences.

Developing new accelerators and new experiments means new configurations and capabilities, so we collaborate with the Environment, Health and Safety Division to bring those on line safely, even including testing of radiation detectors in new regimes of very short pulses. ATAP’s activities are based on a vital partnership with the Engineering Division, which provides advanced design work, dedicated mechanical and electrical shops working hand in hand with experiments, and specialized expertise and collaboration supporting our ability to execute major projects. The Laboratory’s and ATAP’s excellent support staff — including administrative services, finance management, facilities, human resources, communications and lab operations functions — are also essential to our ability to do these things. As Newton put it, we stand on the shoulders of giants. We are grateful to the many people who help us make the climb.

90th Anniversary Accelerator Week: A Conversation with Antoine Wojdyla

Antoine Wojdyla

A Caribbean childhood, a battery, bulb, and wires sparked a curiosity journey that led Antoine Wojdyla to the Advanced Light Source Upgrade Project. The improved capabilities of the upgraded ALS will enable transformative science that cannot be performed on any existing or planned light source in the world. Learn about Antoine’s remarkable path to Berkeley Lab and one of the many ways we are advancing particle accelerators into the next 90 years.

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Antoine Wojdyla grew up in the Caribbean, on the French islands of Guadeloupe and Saint-Martin. He had no scientists in his family as role models, but his interest in the wonders of science were set in motion from his grandfather who was a woodworker. His grandfather built him a toy cart and he added a bulb, battery, and wires. Antoine was amazed at what happened when touching the wires turned the light on and deemed his grandfather a magician. He was informed that it was not magic, but science, that could be learned. He was encouraged to be curious not only by family members, but from teachers and professors.

He moved to mainland France and received his Ph.D. from Ecole Polytechnique, a school near Paris, where he studied terahertz radiation, a kind of electromagnetic wave that sits between infrared and microwaves.

He was interested in terahertz radiation since it can see through materials while producing acceptable resolutions for imaging. This technology is used in body scanners in airports and 5G telecommunications. While this work is not related to his current work at the Lab, his early experience and ideas are transferable to his current work.

One of Antoine’s favorite quotes comes from his colleague and mentor Ken Goldberg. “There are only two kinds of people who really enjoy doing their jobs, baseball players and physicists.” Antoine says he doesn’t know much about baseball, but physics sure is a great occupation.

When did you come to the Lab?
I came to the lab about nine years ago, where I started as a postdoc at the Center for X-Ray Optics, studying extreme ultraviolet (EUV) lithography, which is the latest technology in semiconductor manufacturing. iPhone 12 chips are made using this technology, and the Lab and the ALS have been at the forefront of research in this area. For a while I thought I would bring my scientific expertise to industry, but I realized that the environment at Berkeley Lab was quite unique and would allow me to conduct research better than anywhere else. Plus, we undoubtedly have the best view from our offices, and a community which truly believes in improving the fabric of academia.

Around the same time in 2016, the Advanced Light Source was starting the conceptual design for an upgrade, and I was asked if I wanted to join. It wasn’t a very hard decision to make.

What are you currently working on?
I am currently working on the upgrade of the Advanced Light Source (ALS-U), which is a large-scale DOE project. The goal is to turn the facility from a very fancy flashlight to a laser-like source of x-rays, the so-called “4th generation” of synchrotrons (diffraction-limited storage rings) where we eventually reach the limits of what is permitted by physics.

The project is roughly divided between the accelerator systems and the beamline and optical systems, which I’m part of. My role is to design the new beamlines that will operate on day one after the upgrade, taking advantage of the unique properties of the source. We work with beamline scientist to understand what they want to be able to conduct experiments with what will be the most coherent synchrotron radiation in the world, and together with engineers we define tolerances to provide them what they need based on the state of the art of mechanical and optical engineering: everything has to be very precise – aberration measured in pico-feet and not allowed to move by more than a nano-inch.)

It’s also great to work with colleagues from the accelerator side, learn how they handle electrons and see how we can adapt these techniques to measure our bright photons. We develop new enabling technologies such as x-ray wavefront sensing and adaptive optics, and sometimes borrow ideas, such as using machine learning to compensate for minute deformations caused by every residual drift and non-linearities.

I’m also learning a lot from colleagues from other U.S. light source facilities: there is a great spirit of collaboration at the national level.

What big challenge(s) are you hoping to solve with your work in the next 20 years?
Lately, I’ve been very excited by newly found links between superconductors and knots in the magnetic field called skyrmions and other strange topological effects. Soft x-ray light sources are ideal to look at these topics, and if we can understand how this all works, maybe we could manufacture superconductors working at room temperature.

If we can harness superconductivity, not only could you move energy from sunny to darker places, but you could also have flying cars. The internet brought a nearly frictionless flow of information and changed the world. Imagine what would happen if it was the same for green energy.

I think with laser-like properties of the upgraded ALS, there are many challenges we could tackle beyond better resolution and faster experiments. Things like adaptive optics, which means you literally change the surface of mirrors by a few atoms, could be possible. You could potentially use the light as a tweezer, create phase vortices to twist crystal lattices or, or 3D-print at the nanoscale.

Who from the past, present, or future would you like to collaborate with? And on what?

I want to collaborate with scientists from today! There is such an amazing pool of young scientists, and their make up is more diverse now than ever before. If we can harness the expected boost in science funding, we could change the face of academia. The current global health situation has been difficult for many, but particularly so for young scientists, and I sincerely hope we can make up for the crucial interactions that didn’t happen over the last 20 months.

Events such as the Lab Slam or area-wide seminars are ideal to start such conversation, and I think dissemination of knowledge through communication is very good overall. Thanks to that, I feel that there’s a great soil for collaboration among scientists from various fields, and many times I went on hike with colleagues working in biology or chemistry telling me about their research, and the next month see this kind of research featured in leading journals – understanding why it was relevant, but more importantly how I could help. With the end of Moore’s law, we have also become able to manipulate matter in exquisite ways, and I am very interested in learning more about the latest trends in material sciences.

On a different note, the current climate of information around global warming or public health measures worries me, and it’s inspiring to see scientists from the Lab taking a public role disseminating science ideas. That’s somewhere we can all learn from our colleagues.



Jeroen van Tilborg To Speak at ALS Colloquium Wednesday, Sept. 29

Jeroen van Tilborg

Jeroen van Tilborg

Jeroen van Tilborg, BELLA Center Deputy Director for Experiments, will present “Plasma-Based Accelerators for Future Light Sources: From High-Brightness Injectors to Driving Compact Free-Electron Lasers”  today, Sept. 29, 3-4 p.m. Pacific time. His talk kicks off the Fall 2021 Advanced Light Source Colloquium Series. The talk will be presented via Zoom.






ATAP’s Mitchell Wins Berkeley Lab Director’s Award

Chad Mitchell

Chad Mitchell

Chad Mitchell, a staff scientist in ATAP’s Accelerator Modeling Program, has been honored with the Berkeley Lab Director’s Award in the category of Scientific Achievement.

He leads a team that developed novel beam dynamics methods to significantly extend the reach of future intensity-frontier particle accelerators for high energy physics discovery science, as well as for practical applications of high-intensity (multi-megawatt) proton beams.

To meet the challenges of accelerator facilities at the intensity frontier, it is essential to investigate novel and reliable strategies for controlling space-charge-related beam loss in intense hadron beams. A strategy that stands out for its innovation and far-reaching impact on accelerator design uses nonlinear integrable lattices that introduce large beam tune spread to suppress coherent instabilities that drive the development of beam halo. The team contributed important theoretical and computational tools needed to understand the beam dynamics in accelerators based on this relatively new concept.

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Frontiers in the performance of particle accelerators include not only the energy of their beams, but also the intensity. Both discovery science (e.g., neutrino experiments in high energy physics, and the many applications of beams from spallation neutron sources) and practical applications in nuclear energy are calling for megawatt-plus proton beams. This requires beam intensities that pose dynamics difficulties for the “optics” — the lattice of magnets that bend and shape the beam — used in present-day accelerators.

The proposed solutions include a radical change of paradigm: from the linear focusing beam optics (used in all present circular particle accelerators) to nonlinear “integrable” beam optics. The integrability ensures that particle trajectories are bounded, while the nonlinearity can be tuned to suppress the effect of resonances and the resulting development of beam halo, both of which plague existing accelerators.

The new concept was put forth by V. Danilov (ORNL) and S. Nagaitsev (FNAL) in 2010. Chad proposed a research plan to explore it further and was funded by the prestigious and competitive DOE Early Career Research Program on first submission in 2016. He and his team collaborated with people already investigating collective dynamics of intense beams at Fermilab and RadiaSoft. Much of the Berkeley Lab work involved understanding aspects of the single-particle dynamics that had not previously been explored. This better understanding of the single-particle dynamics allowed them to make sense of aspects of the collective dynamics that they were seeing in simulations. They then led the expansion of this research from previous studies of single particle dynamics into the much more complex area of collective dynamics.

One theme of their work was to understand the interplay between space charge and integrability. In particular, they explored what happens when the integrability is broken in the presence of space charge, both through simulation and by developing a simple model, and we examined these effects in a realistic accelerator lattice (the IOTA ring at Fermilab) using high-fidelity simulation. Both analytical and computational approaches played important roles. As a testament to the quality of their work, in 2020, predictions of phase space bifurcation were borne out by the IOTA experimental team’s observations.

Their work has had major impact on the Fermilab IOTA experimental program and has fostered a new line of research in ATAP, with follow-up work planned that will bring the power of artificial intelligence and machine learning tools to bear and push forward methods to expand the performance envelope of future accelerators.




Machine Learning Team Wins Halbach Award

Preface: ATAP’s long partnership with the Advanced Light Source Division includes accelerator-physics support for that user facility. Co-leader Simon Leemann, postdoctoral scholar Yuping Lu, retiree affiliate Hiroshi Nishimura, and staff scientist Changchun Sun were the ATAP members on a multi-divisional, interdisciplinary research team that the ALS honored this year with the Klaus Halbach Award for Innovative Instrumentation.

“This innovative work exemplifies cross-cutting tools that extend the performance of current systems, and have the power to enable new light sources as well as other accelerator applications of precision beams such as colliders by harnessing increasing complexity,” said Cameron Geddes, director of the ATAP Division.

By Lori Tamura, ALS Communications

Top row: Simon Leemann, Alex Hexemer, Shuai Liu, and Yuping Lu. Bottom row: C. Nathan Melton, Hiroshi Nishimura, Changchun Sun, and Dani Ushizima.

Top row: Simon Leemann, Alex Hexemer, Shuai Liu, and Yuping Lu.
Bottom row: C. Nathan Melton, Hiroshi Nishimura, Changchun Sun, and Dani Ushizima.

The topic of machine learning has been getting a lot of buzz lately — with good reason. At the Advanced Light Source (ALS), a team of accelerator physicists and computer scientists were able to use machine-learning techniques to solve a problem that has plagued third-generation light sources for a long time: fluctuations in beam size due to the motion of insertion devices.

“You look at the data and you realize, holy cow, this thing really just managed to reduce fluctuations by almost an order of magnitude!” said team leader Simon Leemann, deputy of the ALS Accelerator Physics Group. “That was the moment it really kicked in. That was quite special.” Alex Hexemer, a senior scientist who leads the Computing Program at the ALS, served as the co-lead in developing the new tool.

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By improving the stability of the electron beam, the project successfully enhanced the performance of the ALS. As a result, Leemann, Hexemer, and fellow team members Shuai Liu, Yuping Lu, C. Nathan Melton, Hiroshi Nishimura, Changchun Sun, and Daniela Ushizima received the 2021 Klaus Halbach Award for Innovative Instrumentation at the ALS.

“Truly stunning results were achieved after just a few months of effort, and the approach is now codified and embedded in ALS accelerator operation,” wrote ALS Director Steve Kevan in support of the nomination. The experimental results have been described in a study published in Physical Review Letters and in a Berkeley Lab news release.

“Synchrotron facilities such as the ALS deliver light over a broad spectrum to dozens of simultaneous experiments,” said ALS Deputy for Accelerator Operations Fernando Sannibale, who nominated the team for the award. “Each straight-section beamline independently tunes the energy of the photons it delivers by adjusting the magnetic field generated by its insertion-device source.”

Three grayscale panels with decreasing amounts of noise, from left to right; left-most panel shows significant banding
With the machine-learning system off and undulators moving, STXM scans show significant fluctuations of intensity, which can cause artifacts in images of samples. (Credit: Matthew Marcus/ALS)

Such adjustments perturb the electron beam stored in the ALS ring and can affect the overall light-beam performance across the entire facility. In particular, the perturbations strongly and directly affect several classes of beamline experiments that extract the coherent fraction of photons emitted by the source, such as scanning transmission x-ray microscopy (STXM) at Beamline

“Simply put, this will dramatically improve the quality of science our users can do,” said David Shapiro, who leads the Microscopy Program at the ALS. “I have no doubt that these methods will be implemented at all synchrotrons.”

Headshot photos of David Shapiro and Matthew Marcus.
David Shapiro and Matthew Marcus.

From the very beginning, Shapiro and ALS Staff Scientist Matthew Marcus were instrumental to the success of the project. They described the problem from the user perspective, devised measurement protocols, and gathered data during accelerator physics shifts, coordinating measurements with the control room. “None of this work would have been possible without their efforts and commitment,” said Leemann.

Changchun Sun, a staff scientist in the ALS Accelerator Physics Group, was also a key player on the team. “His measurement setup was absolutely critical to the success of this work,” said Leemann. “Without his expertise in imaging our beam and ability to tweak the instrument specifically for this application, we would not have been able to realize the project.”

Initially, Sun was skeptical that this scheme could really work. There are so many parameters to account for, and so many insertion devices, how could an algorithm accurately predict the beam’s fluctuations and then compensate for them in real time? It was Hiroshi Nishimura, an accelerator physicist at the ALS (now semi-retired), who helped turn the corner.

Red line flattens when stabilization is on; blue line fluctuates during the same interval.
Even more impressive than early simulations “in silico,” real-world application of the machine-learning tool yielded impressive improvements in vertical beam size (yellow area). The blue trace is the parameter that is tuned to cancel out fluctuations.

“When something got too complex for traditional methods to work with a reasonable amount of effort, I knew it was time to try machine learning,” said Nishimura. “Many textbook examples were demonstrating the usefulness of machine learning. There was no reason for it not to work like any other accelerator project on paper.”

Nishimura performed some preliminary tests, running historical data through a machine-learning program. The method’s predictive power astonished both Sun and Leemann. “Hiroshi made it work,” said Sun. “Hiroshi and the data, using machine learning, predicted the beam size! That was my turning point, when I knew that machine learning was going to be very useful.”

Nishimura’s interest in applying computer technology to accelerator physics led him to connect, through Hexemer, to Daniela (Dani) Ushizima, a data scientist in the Machine Learning and Analytics Group of Berkeley Lab’s Computational Research Division (CRD). In succession, CRD graduate student Shuai Liu (now at Facebook), ALS postdoc C. Nathan Melton (now at Lawrence Livermore National Laboratory), and postdoc Yuping Lu (currently wrapping up an appointment with the Accelerator Technology and Applied Physics Division) all contributed machine-learning and data-analysis expertise to the effort.

“This sort of work is emblematic of what is needed,” said Ushizima, “close cooperation between domain experts and data scientists, customizing and tailoring techniques to take advantage of scientific information to bring new levels of sophistication to machine-learning methods.”

Left panel shows horizontally wide beam spot. Right panel shows small, round spot.
Comparison of the beam profiles of ALS (left) and ALS-U (right).

As the ALS Upgrade (ALS-U) project moves forward, such collaborations will continue to be crucial. The ALS-U beam will be very different—a point-like vs. a “flat” beam. A flat beam is naturally very stable in the horizontal direction, but after the upgrade, stabilization will be needed in that direction as well. Team leader Leemann is already thinking about how to get it done.

“I’m convinced you can get it to work, but the way you implement the correction and the way you train this machine-learning model has to be adapted to work in both transverse planes,” he said. “It’s not going to be copy-and-paste. We’re going to actually have to develop it. It’s one of the things we want to do in a follow-on project—start developing those ideas.”

Klaus Halbach was a senior staff scientist at LBNL who pioneered the development of undulators using permanent magnets, and other innovations in accelerator physics. Even though he retired from LBNL in 1991, he remained active in lab projects and student training until his death in 2000.




Arun Persaud Recognized as One of Lab’s Outstanding Mentors

Arun Persaud in lab

Looking toward the future of the scientific workforce. (Photo courtesy Arun Persaud)

Arun Persaud, a staff scientist in ATAP’s Fusion Science & Ion Beam Technology (FS&IBT) Program, has been recognized with the Outstanding Mentor Award. The honor, bestowed by the Lab’s Workforce Development & Education Office, recognizes those going above and beyond in 2019 and 2020 to teach technical and professional skills to Berkeley Lab’s undergraduate interns.

In an article on the WD&E website, Persaud noted, “The WD&E program has been a great resource for our group to be able to find highly motivated students.”

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His interns have praised him for being a good listener, taking the time to learn about their technical backgrounds, and helping them build a firm foundation in practical skills. One of his mentees cited his “extraordinary commitment to the success of his interns.” Many come away from the internship experience with publication credits to their name as well — most recently Tanay Tak, who participated in the development of a system for measuring and imaging carbon in soil.

Persaud has had only one intern, who worked remotely, during the Lab’s time of COVID precautions, but said, “We are looking forward to have more students join us when the pandemic is over and it is easier to host them onsite.”

Arun Persaud with recent Summer Undergraduate Laboratory Internship students Tanay Tak (l.) and Lindsey Gordon (Credit: Thor Swift/Berkeley Lab)

Arun Persaud with recent Summer Undergraduate Laboratory Internship students: Left: Tanay Tak. Right: Lindsey Gordon, who he co-mentored.. (Credit: Thor Swift/Berkeley Lab)

“Arun has exemplary talent and enthusiasm for fostering the careers of future scientists.” said ATAP Director Cameron Geddes. “We appreciate his work in mentoring the next generation and in enabling their contributions to science, which are important parts of our mission.”

Success indicator

These are some of the students Arun has mentored in recent years, making further progress toward bright careers in science and technology. (He co-mentored many of them with FS&IBT Program colleagues Peter Seidl, an active retiree, and staff scientist Qing Ji.) Most of these students came to us through the DOE Office of Science Summer Undergraduate Laboratory Internship (SULI) Program. Brian Wynne, William Larsen, and Grant Giesbrecht are recent SULI students who went on to serve as research assistants in the FS&IBT Program.

•  Brian Wynne (Summer 2020, virtually): Incoming PhD student, Princeton University.
•  Danielle Curtis (Spring 2020): Law student, University of Oregon, and Law Clerk, Cascadia Wildlands.
•  Tanay Tak (fall 2019): Entering a PhD program in materials at the University of California-Santa Barbara.
•  Lindsey Gordon (fall 2019; co-mentor): Entering a PhD program in astrophysics at the University of Minnesota.
•  Madeline (Wells) Garske (2019; co-mentor): Accelerator Systems Operator, SLAC.
•  Casey Christian (2019), Post-baccalaureate Research Fellow, Physics Division, Berkeley Lab.
•  Madeline (Wells) Garske (2019): Accelerator Systems Operator, SLAC.
•  Grant Giesbrecht (2019; co-mentor): Accelerator Systems Operator, SLAC.
•  William Larsen (2019): Graduate student, Rice University.
•  Grace Woods (2018): PhD candidate, applied physics, Stanford University.
•  Will Mixter (2018), Product Reliability Engineer, Hunter Industries.
•  Zachary Croft (2018): Graduate student, applied physics, University of Michigan.
•  David Raftrey (2017): PhD student, physics, UC-Santa Cruz and Berkeley Lab.
•  Evan Dowling (2017): Graduate student, physics, University of Maryland.
•  Maya Silverman (2016): PhD student, physics and astronomy, UC-Irvine.
•  Franziska Treffert (2016): PhD candidate, TU-Darmstadt, and Visiting Research Scientist, SLAC.




APS-DPP Launches Pride Committee

DPP Pride Logo

First LGBT+ affinity group in APS

The American Physical Society Division of Plasma Physics Pride Committee is the first affinity group within APS focused on supporting the LGBT+ community, and is working towards a scientific community supportive of scientists in the gender and sexual orientation minority communities. ATAP’s Cameron Geddes — also a member of Lambda Alliance, an Employee Resource Group at Berkeley Lab — was influential in the creation and recognition of the Pride Committee.




Women of the 2010s Features ATAP

The Lab’s 90th anniversary has brought several celebrations of the contributions of women through the decades. The 2010s photostory included a gathering of ATAP’s women scientists and staff members in November 2019.

L-R: Qing Ji, Hangi Feng, Dan Wang, Tianhuan Luo, Asmita Patel, Ina Reichel, Martha Condon, and Laura Desiree Geulig.

L-R: staff scientist Qing Ji, graduate student Hanqi Feng, postdoctoral scholar Dan Wang, research scientist Tianhuan Luo, Deputy Division Director for Operations Asmita Patel, Outreach and Education Coordinator Ina Reichel, Senior Division Administrator Martha Condon, and PhD student Laura Desiree Geulig, November 2019.




In IDEA, words matter. Our choice of words, and of the ideas we express with them, can either uplift others or cause hurt and reinforce stereotypes. In this issue we bring a pair of tools for improving our performance in these matters.

Puncturing Stereotypes and their Impact on Identity

Claude Steele

Stereotypes have a powerful effect and can take on a damaging reality. The result is a distracting kind of pressure to overcome that stock image, which often negatively influence a person’s ability to succeed. So how do we puncture a stereotype? What can be done to get past stereotype threat? Claude Steele, who coined the term “stereotype threat” and who has researched this phenomenon extensively, joins us to answer these and other provocative and important questions. The recorded presentation is part of the Science & Information Exchange, a service of the National Academy of Sciences.

Writing About People With Dignity

Symmetry Magazine, a joint Fermilab-SLAC magazine, has a thought-provoking and useful style guide specifically addressing IDEA topics. Useful for speakers as well as writers, it offers tips to help us communicate in ways that

•   Avoid replicating patterns that have caused harm to the people we write about and to the people who read our writing,
•   Are accurate and avoid inviting readers to make assumptions about individuals and groups, and
•   Uplift in particular individuals and groups who are most affected by the words used to describe them, and who have not always had agency over how they are described.





Recent highlights, in case you missed it…

Successful Tests Pave the Way for Fermilab’s Next-Generation Particle Accelerator

From an article by Diana Kwon in Fermilab Frontiers. A Berkeley Lab radiofrequency quadrupole linac, or RFQ, is a key element of the project.


Looking into the nature of matter involves an intricately shaped accelerating structure called an RFQ. (Credit: Berkeley Lab/Roy Kaltschmidt)

A highly anticipated particle accelerator project at the U.S. Department of Energy’s Fermilab is one step closer to becoming a reality. This spring, amidst the pandemic, testing wrapped up at the PIP-II Injector Test Facility, or PIP2IT. The successful outcome paves the way for the construction of a new particle accelerator that will power record-breaking neutrino beams and drive a broad physics research program at Fermilab over the next 50 years.

The feat was a culmination of over eight years of work on the Proton Improvement Plan-II, or PIP-II, by a dedicated group of scientists, technicians and engineers.
To learn more, visit the Fermilab website…




Ion Beams Enable Developments in Quantum Technology

The article by Joanne Liou of the International Atomic Energy Agency draws upon “Ion Beams Mean Quantum Leap for Color-Center Qubits” and mentions the IAEA Training Workshop on Ion Beam Driven Materials Engineering: New Roles for Accelerators in Quantum Technology, a virtual event May 4-7, 2021, at which ATAP’s Thomas Schenkel was among the lecturers.

Illustration of ion beam treatment of diamond to form qubits

Ion beams can create chains of closely coupled quantum bits (qubits) based on nitrogen-vacancy “color centers” in diamond for use in quantum computing hardware. The honeycomb pattern in the photo shows the difference between areas exposed to the beam (darker) and masked-off areas. Results indicate it should be possible to create 10,000 coupled qubits over a distance of about the width of a human hair, an unrivaled number and density of qubits. (Credit: Susan Brand/Berkeley Lab).

Quantum technology has opened a whole new world of potential advances in secure communications, information technology and high precision sensors. This technology is poised to provide solutions to some of the most pressing challenges in health care, industry and security. Ion beams find application in developing the innovative materials needed for new quantum technologies.

“The IAEA is fully engaged with worldwide initiatives in quantum technology,” said Aliz Simon, a nuclear physicist at the IAEA. “Ion beam accelerator techniques offer emerging opportunities to further explore and develop research in quantum technology.”
“Quantum technology is going through a transformation and time of rapid progress,” Schenkel said. “There is the question of how we will use it; it has the potential to be used for the betterment of humankind and the advancement of our civilization.”

To learn more, visit the IAEA website…



Berkeley Lab, UC Berkeley, Caltech To Build Quantum Network Testbed

— Five-year, $12.5 million U.S. Department of Energy project will help pave the way for a nationwide quantum Internet
From an article by Kathy Kincade of Berkeley Lab Computing Sciences. ATAP’s Thomas Schenkel is a co-investigator on the project, known as QUANT-NET.

Abstract rendering meant to evoke quantum network

QUANT-NET to entangle Lab, Cal

Berkeley Lab and UC-Berkeley will be home to a cutting-edge quantum network testbed, thanks to a new five-year, $12.5 million funding award from the U.S. Department of Energy (DOE).

Led by personnel from Berkeley Lab’s Scientific Networking Division/ESnet, UC Berkeley, and Caltech, the R&D collaboration will also leverage quantum development efforts at Berkeley Lab and beyond.





Welcome to 3Q4, in which a few questions help us get to know the people behind the science. In this issue we meet Ina Reichel, Outreach and Education Coordinator on ATAP’s Operations team.

Detail of Ina wearing Bohus Stickning sweater

Yarn with a tale to tell

In this detail from the “Women of the 2010s” photostory on the Berkeley Lab 90th Anniversary website, Reichel, a knitting enthusiast, wears a favorite sweater — a classic design from Bohus Stickning cooperative, a cottage industry that empowered impoverished women in Sweden’s Bohüslan province. A 1995 book led to a revival of interest in their distinctive style, and now kits are available for many of their designs. Hers is made from one of those kits and she has another kit waiting at home.

Reichel earned a PhD from Aachen based on work at CERN, came to the US as a postdoctoral fellow at SLAC, then joined Berkeley Lab to work in ATAP’s Center for Beam Physics. Now (among many endeavors) she furthers both K-12 outreach and IDEA advancement in the workplace, and is a member of the Division’s social-media team.

Since this is Safety Week in the Physical Sciences Area, we will start with one of the many interests of the self-described “physicist, mom, wife, knitter, backpacker, EMT”: emergency preparedness.

You’ve carried altruism to a high degree by training as an EMT and in
Wilderness First Aid and volunteering on the Lab’s (since discontinued) Medical Emergency Response Team. What suggestions would you have for someone who wants to be prepared to help themselves and others in an emergency?

I think a good way to start is joining your local Community Emergency Response Team (CERT). It’s a free 16 hour training usually run by the local fire department plus an all-day Saturday drill where you get to practice some of the things you learned. It’s also a good way to meet other people living in your neighborhood. After a big earthquake, professional emergency responders will likely be overwhelmed. CERT teams can jump in and help their neighbors doing triage and first aid as well as some light search and rescue. There is also a CERT team at the Lab.

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If you are willing to spend more time on volunteering, joining a county’s Medical Reserve Corps (MRC) is a good option. The minimum requirement for people without a medical licence is a Basic Life Support CPR card. It requires a three hour class with a written test or an online class/test with a 30 minute in-person skills verification. The card is good for two years.

I volunteer with the Contra Costa MRC. In normal times they do some flu shot clinics in fall, and teach “Stop the Bleed” classes (mostly at high schools). During fire season they provide medical staff to emergency evacuation shelters all across northern California (and sometimes even southern California). In normal years they provide between 1500 and 2000 volunteer hours, most of that being at the evacuation shelters.

During the pandemic, their nurses taught courses on the proper use (including donning and doffing) of PPE for staff members in the county’s residential elder care facilities. Additionally, they ran (and are still running) COVID vaccine clinics. They ran clinics in most of the county’s residential elder care facilities to get residents and staff vaccinated, and they are still running equity clinics in underserved parts of the county to reach as many people as possible.

For anyone enjoying hiking or backpacking in areas with no cell phone signal, I highly recommend taking a Wilderness First Aid class. They are 16 hours long and are usually taught in a single weekend. They can be hard to find on a regular basis for the general public, but REI offers them in the Bay Area monthly, rotating among locations (including one close to Berkeley).

As both an accelerator physicist and the mother of someone now in his sophomore year in college, you bring an interesting set of experiences to your job as our Outreach and Education Coordinator. What are the opportunities and
challenges you see in that role?

When our son was younger, the Lab didn’t yet have its back-up care program, so my husband (also a Berkeley Lab physicist) and I had to sort out who works from home that day. He usually had more meetings than me, and that was before Zoom was a thing, so I was often the one staying home. Try programming some difficult code while sitting in an armchair with a sick toddler on your lap who wants to snuggle, balancing your laptop on the armrest! As a result, I really understand the challenges of parents of younger children during the pandemic. I am so grateful that my son did not really need much supervision or help while attending his last few months of high school from home during the pandemic. But I do feel for the parents of younger children who suddenly have many more caregiving and/or teaching duties than they did pre-pandemic.

Ina Reichel, youngsters at Daughters and Sons to Work Day

Reichel is a regular at the Lab’s educational outreach events. Here she demonstrates cryogenics using a balloon that had been frozen in liquid nitrogen.

Because my job has me plugged into the science education network in the Bay Area, I have a good overview of what programs are around, both for families and for schools. This allowed me to hook up my son’s school to enrichment programs and exciting field trips the teachers might otherwise not have known about.

You’ve been very active in our IDEA programs, notably the Women Scientists and Engineers Council (WSEC). What advice would you give to young women considering a career in these fields, and what can the rest of us do to foster their success and help make this a better workplace for all?

Awareness of imposter syndrome, microaggressions, and implicit bias are three important things.

A few years ago WSEC had a workshop on imposter syndrome, although that expression was not in the title or description. Once the instructor had explained imposter syndrome to the group, a large number of attendees (and not just the young ones) were like, “wait, I am not the only one who is feeling that way? This is so common it actually has a name?”. So one of my recommendations is to learn about imposter syndrome and how to recognize it when it is happening to you.

I sometimes still struggle with it after more than a quarter century as a physicist. Interestingly, as an EMT, I started out with a really bad case of it, but there I can actually recognize it now. I can realize, “this is just my imposter syndrome talking,” and in most cases I can tell it, “I am a competent EMT, I can handle this.” (Or, to use a German saying, die anderen kochen auch nur mit Wasser, which approximately translates to, “the others only use water for boiling as well”).

Another thing to learn about is microaggression (not just against women but against other minorities as well). Learn not to perpetrate microaggressions, and be an upstander if you see them happening. And learn about implicit bias. We all have it, but if we know about it, we can try to counteract it.





Refereed literature

A. Myers, A. Almgren, L.D. Amorim, J. Bell (LBNL); L. Fedeli (CEA); L. Ge (LBNL and SLAC); K. Gott (LBNL); D.P. Grote (LLNL); M. Hogan (SLAC); A. Huebl, R. Jambunathan, R. Lehe (LBNL); C. Ng (SLAC); M. Rowan, O. Shapoval (LBNL); M. Thévenet (DESY); J.-L. Vay (LBNL); H. Vincenti (CEA); E. Yang (LBNL); N. Zaim (CEA); W. Zhang, Y. Zhao and E. Zoni (LBNL), “Porting WarpX to GPU-accelerated platforms,” Parallel Computing (in press), pre-proof available 14 September 2021.

Lipeng Wan (ORNL); Axel Huebl, Junmin Gu (LBNL); Franz Poeschel (HZDR); Ana Gainaru, Ruonan Wang, Jieyang Chen (ORNL); Xin Liang (Missouri University of Science and Technology); Dmitry Ganyushin (ORNL); Todd Munson (ANL); Ian Foster (University of Chicago); Jean-Luc Vay (LBNL); Norbert Podhorszki (ORNL); Kesheng Wu (LBNL); and Scott Klasky (ORNL), “Improving I/O Performance for Exascale Applications through Online Data Layout Reorganization,” IEEE Transactions on Parallel & Distributed Systems, early access (29 July 2021).

L. Fedeli, A. Sainte-Marie, N. Zaim, M. Thévenet, J. L. Vay, A. Myers, F. Quéré, and H. Vincenti, “Probing strong-field QED with Doppler-boosted petawatt-class lasers,” Physical Review Letters 127, 114801 (10 September 2021), .
See feature article in this issue of ATAP News

R. Teyber, L. Brouwer, J. Qiang, and S. Prestemon, “Inverse Biot-Savart Optimization for Superconducting Accelerator Magnets,” IEEE Transactions on Magnetics 57, 9 (Sept. 2021),

M. Turner, A. J. Gonsalves, S. S. Bulanov, C. Benedetti, N. A. Bobrova, V. A. Gasilov, P. V. Sasorov, G. Korn, K. Nakamura, C.G.R. Geddes, C.B. Schroeder, E. Esarey, “Radial density profile and stability of capillary discharge plasma waveguides of lengths up to 40 cm,” High Power Laser Science and Engineering, 9, 2:02000e17 (28 April 2021)

V. Ranjan, B. Albanese, E. Albertinale, E. Billaud, D. Flanigan (CEA Saclay); J.J. Pla (University of New South Wales); T. Schenkel (LBNL); D. Vion, D. Esteve, E. Flurin (CEA Saclay); J.J.L. Morton (University College London); Y.M. Niquet (Université Grenoble Alpes) and P. Bertet (CEA Saclay), “Spatially Resolved Decoherence of Donor Spins in Silicon Strained by a Metallic Electrode,” Physical Review X 11, 031036 (16 August 2021),


Amit Lal (Cornell University); Thomas Schenkel, Arun Persaud, Qing Ji, Peter Seidl, Will Waldron (LBNL); Serhan Ardanuc, Vinaya Kumar Kadayra Basavarajappa (Cornell University), “Wafer-based charged particle accelerator, wafer components, methods, and applications,” publication date 2021/2/2, US Patent Number 10912184 (application number 16538563)

Unrefereed Proceedings

K. Hwang, “Analysis of the Chromatic Vertical Focusing Effect of Dipole Fringe Fields,” in Proceedings of the 2021 International Particle Accelerator Conference (virtual; hosted by LNLS/CNPEM, Campinas, Brazil, 24-28 May 2021), MOPAB234 (JACoW, August 2021).

K. Hwang, “Transverse 2D Phase Space Tomography Using Beam Position Monitor Data of Kicked Beams,” in Proceedings of the 2021 International Particle Accelerator Conference (virtual; hosted by LNLS/CNPEM, Campinas, Brazil, 24-28 May 2021), MOPAB235 (JACoW, August 2021).

C. Mitchell, K. Hwang, and R. Ryne, “Model of Curvature Effects Associated with Space Charge for Long Beams in Dipoles,” in Proceedings of the 2021 International Particle Accelerator Conference (virtual; hosted by LNLS/CNPEM, Campinas, Brazil, 24-28 May 2021), WEPAB249 (JACoW, August 2021).

C. Mitchell, K. Hwang, and R. Ryne, “Kurth Vlasov-Poisson Solution for a Beam in the Presence of Time-Dependent Isotropic Focusing,” in Proceedings of the 2021 International Particle Accelerator Conference (virtual; hosted by LNLS/CNPEM, Campinas, Brazil, 24-28 May 2021), WEPAB248 (JACoW, August 2021).

M.P. Ehrlichman, S. De Santis, T. Hellert, S.C. Leemann, G. Penn, C. Steier, C. Sun, M. Venturini, D. Wang, “Multi-Bunch Resistive Wall Wake Field Tracking via Pseudomodes in the ALS-U Accumulator Ring,” in Proceedings of the 2021 International Particle Accelerator Conference (virtual; hosted by LNLS/CNPEM, Campinas, Brazil, 24-28 May 2021), WEPAB123 (JACoW, August 2021).

M.P. Ehrlichman, T. Hellert, S.C. Leemann, G. Penn, C. Steier, C. Sun, M. Venturini, D. Wang, “The Three Dipole Kicker Injection Scheme for the ALS-U Accumulator Ring,” in Proceedings of the 2021 International Particle Accelerator Conference (virtual; hosted by LNLS/CNPEM, Campinas, Brazil, 24-28 May 2021), WEPAB124

Y. Lu, M.P. Ehrlichman, T. Hellert, S.C. Leemann, H. Nishimura, C. Sun, M. Venturini
G. Penn, M.P. Ehrlichman, T. Hellert, C. Steier, C. Sun, M. Venturini, and D. Wang, “The Impact of Short-Range Wakes on Injection Into the ALS-U Accumulator Ring,” in Proceedings of the 2021 International Particle Accelerator Conference (virtual; hosted by LNLS/CNPEM, Campinas, Brazil, 24-28 May 2021), MOPAB118 (JACoW, August 2021).

D. Wang, K.L.F. Bane, R. Bereguer, T. Cui, S. De Santis, P. Gach, D. Li, T.H. Luo, T. Miller, T. Oliver, O. Omolayo, C. Steier, T.L. Swain, M. Venturini, G. Wang, “The Broad-Band Impedance Budget in the Storage Ring of the ALS-U Project,” in Proceedings of the 2021 International Particle Accelerator Conference (virtual; hosted by LNLS/CNPEM, Campinas, Brazil, 24-28 May 2021), WEPAB081 (JACoW, August 2021).

D. Wang, K.L.F. Bane, S. De Santis, M.P. Ehrlichman, D. Li, T.H. Luo, O. Omolayo, G. Penn, C. Steier, M. Venturini, “Single Bunch Instability Simulations in the Storage Ring of the ALS-U Project,” in Proceedings of the 2021 International Particle Accelerator Conference (virtual; hosted by LNLS/CNPEM, Campinas, Brazil, 24-28 May 2021), WEPAB082 (JACoW, August 2021).

Rohan Sanghvi, Di Ni, Ved Gund (Cornell University); Qing Ji, Thomas Schenkel (LBNL); Khurram K. Afridi, Amit Lal and Elaine Petro (Cornell University), “Application of Microelectromechanical-system based RF Linear Accelerators for Ultra-High Specific Impulse Ion Micropropulsion,” American Institute of Aeronautics and Astronautics Propulsion and Energy 2021 Forum (virtual event, 9-11 August 2021), IAA 2021-3246 (28 July 2021),





Physical Sciences Area and ALS-U Safety Week Features Seminars, Cleanup, Training

ATAP’s traditional Safety Day is Safety Week this year — a day’s effort distributed over the final week of September this year to give the flexibility needed to work in a socially distanced manner. The ATAP, Engineering, and Physics Divisions and the ALS-U Project will be participating in this year’s event.

The investment of about 0.5% of the work year brings the benefits of cleanliness, organization and up-to-date training to our labs, shops, and offices.

Safety Week will feature midday Zoom seminars to enhance our understanding and keep the momentum going.

Kelly Perce

Kelly Perce

Janie Pinterits

Janie Pinterits

Aditi Chakravarty

Aditi Chakravarty

Tuesday, September 28th, 11:00 AM to noon: IDEA Focus

In support of the Lab’s strategic priority of Inclusion, Diversity, Equity, and Accountability, we had a discussion featuring Moving from Bystander to Upstander with Aditi Chakravarty, Janie Pinterits, and Kelly Perce.

Wednesday, September 29th, 11:00 AM to noon: Special seminar for Chemical Owners and Satellite Accumulation Area (SAA) Owners

Presented by EHS subject-matter experts.

Blair Edwards

Blair Edwards

James Nunez

James Nunez

Wednesday, September 29th, 12 noon to 1:00 PM: Security & Emergency Preparedness

Featuring Berkeley Lab Protective Force Manager Blair Edwards and Emergency Manager James Nunez. Zoom link

Dr. Timur Durrani, MD

Timur Durrani, MD

Maria Nappi

Maria Nappi

Paul Blodgett

Paul Blodgett

Brandon DeFrancisci

Brandon DeFrancisci

Thursday, September 30th, 12 noon to 1 PM: COVID-19 Q&A

Panel discussion with subject-matter experts.

Zoom link

Picture of Pat Thomas

Pat Thomas

Asmita Patel

Asmita Patel

Friday, October 1st, 1:00 to 2:00 PM: Safety Week NOT-Jeopardy Game

What is a fun close-out event hosted by Asmita Patel and Pat Thomas? Test your safety and trivia knowledge! Zoom link



On the Anniversary of Loma Prieta, Let’s Shake Out Our Quake Preparedness

October brings the anniversary of the 1989 Loma Prieta earthquake. Beyond the in-the-moment essentials of “duck, cover, and hold on,” it’s a great opportunity to review all our measures to prepare before, survive during, and recover after.

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Earthquakes: Not If — When

The Hayward Fault runs between the Lab and campus (it actually goes through Memorial Stadium). Seismologists estimate that there is more than a 70% chance of a damaging earthquake striking our region in the next 20 years. The Lab takes extensive quake-preparedness measures, and prudent employees may choose to keep individual supplies in their work areas and cars as well as at home.

In the event of a quake, drop, cover, and hold on. When the shaking stops, grab essential personal items and find a safe route to the evacuation area outside your building. Do not re-enter the building until cleared to do so by safety officials. Hazardous conditions might exist, and there could be aftershocks.

Please take a moment to view this LBNL video about how to prepare for and respond to a real earthquake.

To help you be prepared at work, at home, and in the car, resources are available from the Earthquake Country Alliance (a suggested first thing to read is Putting Down Roots in Earthquake Country, which they repost from the US Geological Survey).

Another useful source of readiness tips for all kinds of disasters and setbacks is 72 Hours, named after the bare minimum amount of time you should be prepared to survive any form of widespread disaster, anywhere, before help arrives. A full week would be even better.

Observing how people coped with the recent Public Safety Power Shutoffs is an excellent guide as well. A way to charge cell phones, a full tank of gas in the car, a stash of nonperishable food and potable water… this is a good basis for any emergency.


Wildlands Fire: Be Aware and Prepared

helicopter over a forest fire

After this summer, and in fact the last few years, surely we’re all painfully aware of the risk of wildfire in California. However, it isn’t just a threat off in the mountains and wilderness — the inner Bay Area, including the vicinity of the Lab, is at risk.

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Although October is the heart of the classic California fire season (it is when the the Oakland/Berkeley Hills wildfire of 1991 occurred), Lab Fire Marshall Todd LaBerge, PE, points out that the risk is tantamount to year-round now. A video of a presentation by LaBerge is a great way to get started learning more about wildfire risks and mitigations.

The Berkeley Lab site is in a vulnerable area (in 1923, a conflagration swept down what was then an empty hillside where the Lab now stands, and was stopped just short of the campus — not by the puny hands of humans so much as by the Diablo winds’ giving way to onshore flow). Many of us also live in or commute through the urban/wildlands interface and have to be aware and prepared for the risk of wildfire.

Know Where You’ll Be SAFE

SAFE Buildings shown in dark blue offer best wildfire shelter

In a call that experts will make depending on circumstances, our Protective Action in case of wildfire might be to shelter in place (as opposed to a managed zone-by-zone or complete evacuation).

Certain structures (at least one in each zone) have been analyzed and designated as Safety Areas For Emergencies (SAFE) buildings. Shown in blue on this map, they are preferred locations for hunkering down until wildfire danger has passed.

Learn to Prepare and Survive

homewildfire_150x143yIf you live in a vulnerable area, clear defensible space and remove light fuels.

Cal Fire’s Ready, Set Go program is an excellent resource, as is the National Fire Protection Associations Firewise USA. The University of California has peer-reviewed advice on how to prepare your home and its landscape for greater fire safety.