ATAP News, September 2021

“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.”

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.

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).

Lasers probe some of nature’s most jealously guarded secrets

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.

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).

“How AMReX is Influencing the Exascale Landscape,” an interview with Andrew Myers of Berkeley Lab’s Center for Computational Sciences and Engineering, discusses how that high-performance-computing software framework co-evolved with WarpX.

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.

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.

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.

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.”

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 5.3.2.2.

“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.”

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.

“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.”

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.

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: 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.

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.

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.

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.

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
If 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.