Following two years of installation, researchers successfully commissioned iP2 and produced high-energy ion beams this fall. The upgrade expands opportunities for scientists who use DOE’s LaserNetUS, a collection of laser facilities across the United States.

“We’re ushering in a new era of high-intensity laser experiments,” said Cameron Geddes, director of Berkeley Lab’s Accelerator Technology and Applied Physics (ATAP) Division, which manages the BELLA Center. “This is a great milestone that broadens the whole science reach of the facility and the possibilities for our field.”

The upgrade, funded through DOE’s Fusion Energy Sciences program, is the second completed at BELLA in 2022. This summer, teams also finished adding a second beamline where researchers plan to stack laser-powered modules to make small, high-energy electron accelerators.

Postdoctoral researcher Sahel Hakimi and graduate student Jared De Chant (from left) make adjustments to iP2 at BELLA. The new facility will expand research capabilities for Berkeley Lab and the LaserNetUS community. (Credit: Marilyn Sargent/Berkeley Lab)

Cancer cells, qubits, and magnetic tornadoes

Researchers already have a number of experiments lined up at iP2 that will take advantage of the laser’s high-energy and its ability to fire quickly (about once per second), delivering particle blasts that last femtoseconds (quadrillionths of a second). The system at iP2 can also focus the laser down to a minuscule size: about 3 microns, a fraction of the width of a human hair.

One of the first experiments will explore what’s known as the FLASH effect, a phenomenon where radiation delivered by protons in an intense, short burst can kill cancer cells while sparing the healthy tissue nearby. In 2020, researchers at BELLA’s original interaction point (iP1) saw promising results looking at thin layers of cells in Petri dishes. They now plan to use protons with more energy to study the FLASH effect in thicker skin and tumor tissue.

“We are investigating the potential of using these laser-accelerated protons for radiotherapy, which would require significantly higher proton energies to penetrate deep into the human body,” said Lieselotte Obst-Huebl, a research scientist in ATAP at Berkeley Lab who led the installation work at iP2. “This is basic research and is in its infancy, but it could potentially someday be a powerful tool in our toolkit.”

Other groups are interested in using the facility to create and test new materials. These could be useful in making qubits, the building blocks of quantum computers, or in high-temperature superconductors, which would carry electricity efficiently without needing to operate in extreme cold. Researchers plan to fire the laser into thin sheets of material such as boron or gold, accelerating the resulting ions and embedding them in targets like silicon wafers or synthetic diamonds. They can then study how these doped materials respond and see whether they have any helpful properties.

Teams are also planning to explore an area known as high energy density science: the study of matter under extreme pressure or density. Among them are certain plasmas, gas-like collections of electrically charged particles. Understanding these incredibly hot (relativistic) plasmas made in the lab could help advance fusion energy sciences, studies in astrophysics (like how stars are born), and the next generation of particle accelerators.

Scientists at BELLA are already combining lasers and plasmas to reduce the size of particle accelerators for lightweight particles such as electrons. New techniques could further improve their power. Researchers will set up experiments at iP2 to study one method called magnetic vortex acceleration (MVA), which could produce more energetic proton and ion beams. They’ll test out special thin, foam-like targets that will interact with the laser to generate rotating magnetic fields that swirl through the plasma like a tornado.

“With MVA, the idea is to absorb as much laser energy as possible into the electrons to create this magnetic vortex through the target that then accelerates the ions with it,” Obst-Huebl said. Boosting particles to higher energies in a shorter distance means new applications and potentially lower-cost ways to explore the fundamental workings of our universe.

Simulations and expansions

Most of the processes studied at BELLA take place over incredibly short periods: around one millionth of one millionth of a second. As a result, it can be difficult to physically measure every aspect, so scientists need to pair their experiments with simulations on some of the most powerful computers in the world to better understand what’s happening.

“It’s complicated physics, and 3D simulations of this type of experiment are relatively new,” said Jean-Luc Vay, head of the ATAP Accelerator Modeling Program at Berkeley Lab. “We’re ready to do the simulations on new exascale computers in support of iP2 experiments.”

Computer modeling was also key to successfully installing the iP2 upgrade during the pandemic, when fewer people were on site. Simulations helped the team plan the experimental setup to measure key plasma and beam properties, and can be used to prepare for future experiments at iP2.

“We have this nice setup, but we don’t yet have all the diagnostic tools,” said Axel Huebl, a computational physicist in ATAP at Berkeley Lab. “So, in parallel with the experiments, we’re getting ourselves ready to build a fully digital twin so that we can measure as many virtual diagnostics in the simulations as possible.”

The simulations will let researchers look at detailed plasma behaviors at any timescale, which they can then compare with measurements from experiments. The results will prove or improve scientists’ best models and feed into other areas of science.

Researchers can submit proposals through LaserNetUS to conduct research at the BELLA Center and take advantage of the expansion at iP2.

“People can bring detectors and new targets and get supported by our team here,” said Kei Nakamura, the associate deputy director for experiments at the BELLA Center. “They can propose pure acceleration experiments or applications of accelerated particle beams. Topics we don’t even know now will be happening in the future.”

Scientists will use the upgraded ALS for research spanning biology; chemistry; physics; and materials, energy, and environmental sciences. The brighter, more laser-like light will help experts better understand what’s happening at extremely small scales as reactions and processes take place. These insights can have a huge array of applications, such as improving batteries and clean energy technologies, creating new materials for sensors and computing, and investigating biological matter to develop better medicines.

“That’s the wonderful thing about the ALS: The applications are so broad and the impact is so profound,” said Dave Robin, the project director for the ALS upgrade. “What really excites me every day is knowing that, when it’s complete, the ALS upgrade will enable researchers to make scientific advances in many different areas for the next 30 to 40 years.”

The DOE approval, known as Critical Decision 3 (CD-3), formally releases funds for purchasing, building, and installing upgrades to the ALS. This includes constructing an entirely new storage ring and accumulator ring, building four feature (two new and two upgraded) beamlines, and installing seismic and shielding upgrades for the concrete structure housing the equipment. The $590 million project is the biggest investment at Berkeley Lab since the ALS was built in 1993.

“Our team has spent years designing every single magnet, vacuum system component, RF [radio-frequency] cavity, power supply, and the rest of the custom design,” said Robbie Leftwich-Vann, Berkeley Lab’s project manager for the upgrade. “It’s exciting to get off the paper and into the world of installing things and making it real.”

Brighter beams, better science

The ALS generates X-rays by circulating electrons through a 600-foot-circumference storage ring. As the electrons travel through this series of magnets, they radiate light along beamlines to stations where researchers conduct experiments. The light comes in many wavelengths, but the ALS specializes in “soft” X-rays that reveal the electronic, magnetic, and chemical properties of materials.

The upgraded ALS will use a new storage ring with more advanced magnets that can better steer and focus the electrons, in turn creating brighter, tighter beams of light. This will squeeze the X-ray beams from about 100 microns (thousandths of a millimeter) to only a few microns wide, meaning researchers can image their samples with even finer resolution and over shorter timescales. It’s like switching from a cell phone camera in dim light to a top-of-the-line high-speed camera in vivid daylight.

The beam profile of Berkeley Lab’s Advanced Light Source today (left), compared to the highly focused beam (right) that will be available after the upgrade. (Credit: Berkeley Lab)

“With the upgrade, we’ll be able to routinely study how samples change in 3D – something that is currently very difficult to do,” said Andreas Scholl, a physicist at Berkeley Lab and the interim division director for the ALS. “One of our goals is to find and develop the materials that will be essential for the next generation of technologies in areas like energy storage and computing.”

With 40 beamlines and more than 1,600 users per year, the ALS supports a variety of research. For example, researchers can look at how microbes break down toxins, study how substances interact to produce better solar cells or biofuels, and test magnetic materials that could have applications in microelectronics. Teams will build two new beamlines optimized to take advantage of the improved light, and realign and upgrade several existing beamlines.

The ALS will use a technique called “on-axis swap-out injection” developed by scientists at Berkeley Lab. It will enable the accumulator and storage rings to work together to create incredibly bright, ordered beams for research that can reveal nanoscale details in materials and reactions.

One crucial element of the upgrade already underway is a second ring known as the accumulator, which will take electrons made by the accelerator complex and prepare them for the new storage ring. Construction began on the accumulator in 2020 with a special advance approval known as CD-3a. By installing and testing the accumulator first, teams can minimize how long ALS operations will be paused to complete the upgrade.

Building a ship in a bottle

If you’ve ever tried to maneuver large furniture into a second-floor apartment, you understand a taste of what installing the new ALS storage ring will involve.“The biggest challenge for ALS-U is space,” said Daniela Leitner, who leads the removal and installation team for the project. “We are literally measuring whether we can put a hand into a particular area.”Many elements in the accelerator tunnel can’t be moved, including the new accumulator ring that will run along the inner tunnel wall. Experts have used extensive modeling and simulations to make sure that the current storage ring can be safely removed along designated access paths and replaced with the new rafts of magnets.

This animation shows a section of storage ring traveling through the accelerator tunnel. The accumulator ring is visible at the bottom. Simulations ensure all the different pieces of the upgrade will be able to travel in and out of the cramped space. (Credit: Christopher Bullock/Berkeley Lab)

Over the next three years, teams will procure and build all of the pieces for the new storage ring and other improvements. With everything prepared, the ALS will enter roughly one year of “dark time” for installation and initial commissioning.

“When the accelerator shuts down, the clock starts,” Leitner said. “Things need to run like a choreographed ballet.”Four teams working in parallel will strip out the current ALS storage ring. That means moving almost 500 tons of equipment, including magnets, cables, and support girders (which will need to be plasma cut into three pieces before they can be extracted). Then they’ll move in 500 tons of state-of-the-art equipment, carefully connect all the components, and bring an improved ALS back to life. It will then be the most intense source of coherent (laser-like) soft x-rays in the world.

“Preparing for this upgrade has been a lab-wide effort that is going to have a great impact on the scientific community,” Witherell said. “I congratulate the entire ALS-U team on their commitment and hard work.”

Use your mouse to navigate the tunnels of the ALS. (Credit: Matterport for Berkeley Lab) 
The Advanced Light Source is a DOE Office of Science User Facility.To learn more about ALS-U:

 • Overview: The Advanced Light Source Upgrade (ALS-U) project

 • Video: Toward a New Light: ALS Upgrade Project Moves Forward

Pushing the boundaries of laser-based electron accelerators… and of codes

The team led by Jean-Luc Vay, head of ATAP’s Accelerator Modeling Program, collaborated with the team of Henri Vincenti, physicist and research director at CEA (the French Alternative Energies and Atomic Energy Commission) and other key organizations.

Vay said the research, which builds on and extends earlier work by his and Vincenti’s teams, presents a first-of-kind mesh-refined massively parallel particle-in-cell (PIC) code for kinetic plasma simulations, optimized on a quartet of supercomputers that includes Frontier, Fugaku, Summit, and Berkeley Lab’s Perlmutter. “In addition to melding mesh refinement with PIC codes, developing such a simulation code that runs efficiently at scale is completely new.”

“We’re really pushing here – in three directions,” Vay added. Those directions are improving the state of the art in particle accelerators, notably including laser-driven machines like those being developed at ATAP’s BELLA Center, while at the same time operating on the cutting edge of algorithms and developing a versatile code that is compatible with different types of supercomputers.

WarpX “enabled 3D simulations of laser-matter interactions on Frontier, Fugaku, and Summit, which have so far been out of the reach of standard codes,” the researchers write in the paper’s abstract. “These simulations helped remove a major limitation of compact laser-based electron accelerators, which are promising candidates for next-generation high-energy physics experiments, ultra-high dose rate FLASH radiotherapy, and other applications.”

Improved radiotherapy in a FLASH

In FLASH radiotherapy, a therapeutic dose is delivered in a very short time (a few seconds) at a much higher dose-rate than in conventional treatment protocols. After decades of anecdotal reports on the FLASH radiotherapy effect, more recent experiments have demonstrated a strong difference in sensitivity of healthy and unhealthy tissues to ionizing radiation delivered within short and bright pulses. However, to date, mechanisms behind the benefits of ultra-high dose rate radiotherapy have not been elucidated. This understanding requires a deeper insight into the basis of radiation toxicity on biological samples at disparate timescales, ranging from the femtoseconds (molecule excitation) to the hour (cellular response) and beyond.

Toward this end, the teams led by Vay and Vincenti used complex WarpX simulations to model a novel conceptual design of a laser-based electron injector and accelerator. This design can produce highly charged and very short particle electron beams of high quality that have the potential to deposit a large enough therapeutic dose at ultra-high peak dose rates in tumor cells without damaging other cells.

By using plasma mirrors, the team’s accelerators can deliver a much larger dose of energy in a much shorter time than current conventional methods. Moreover, in order to penetrate deeper into the human body and treat tumors, very large and costly accelerating structures are currently necessary.

“With laser plasma accelerators,” Vincenti said, “we can shrink the distance and enable very high-energy electrons to … democratize, let’s say, FLASH radiotherapy in medical centers at a cheaper cost and at a smaller scale.”

Other potential applications include the building of miniature x-ray free electron lasers for the science of ultrafast phenomena, as well as the development of particle colliders that could be more compact and — the hope is — cheaper than the current generation. To be sure, putting the HEP applications into practice may still take decades.

“This is, I would say, really at the research level of maturity, and computer simulations are key to establishing that it can be done,” Vay said. “It’s very promising.”

Labwide and international synergy of expertise for better modeling

Modeling the project presented a challenge. The main obstacle in modeling the plasma mirror design stemmed from the huge interval of spatial and temporal scales, the scientists noted. To help overcome that hurdle, the team used WarpX, a code developed via their ECP project, Vay noted. WarpX combines the adaptive mesh refinement (AMR) framework AMReX, developed at Berkeley Lab, with novel computational techniques. AMR is akin to a computational microscope, allowing researchers to zoom in on specific regions of space. Berkeley Lab’s Andrew Myers and Weiqun Zhang, both key members of the AMReX development team, are co-authors on the WarpX paper.

This short video celebrating the unveiling of the National Energy Research Supercomputing Center’s Perlmutter system features Axel Huebl and WarpX simulations of particle accelerators. The Accelerator Modeling Program’s WarpX code had the honor of being among the first batch of jobs in the inaugural run of Perlmutter at its May 27, 2021 dedication.

“AMReX is a numerical library that helps us implement physical block-structured mesh refinement algorithms,” said Axel Huebl, a computational physicist at Berkeley Lab who is now a lead developer of WarpX and co-lead author of the Gordon Bell paper. “Mesh refinement enables us to focus the computational power on the most interesting parts of a simulation, while staying effective for the larger, macroscopic evolution of, for instance, the plasma physics we model.”

Though work on this paper began in the spring of last year, its foundation was laid through the group’s affiliation with the ECP. “It’s really years of hard work from many people,” Vay said, adding that the team recently also had to pull long shifts to make efficient use of the various supercomputers when they gained access for brief windows of time.

Thanks to the ongoing collaboration through CEA and RIKEN, the researchers had full access to Fugaku, located in Japan, for 12-hour spans. “We had to stay connected on the machine to follow our simulations,” said lead author Luca Fedeli, a plasma physicist, WarpX developer, and currently a post-doc at CEA. “So we had like 12-hour Zoom calls at weird times.”

A broad spectrum of emerging and potential applications

WarpX is a cutting-edge software platform developed under Vay’s leadership within DOE’s Exascale Computing Project (ECP) for the modeling of plasma accelerators. It is now being leveraged by the Collaboration for Advanced Modeling of Particle Accelerators (CAMPA)—also led by Vay, and part of DOE’s Scientific Discovery through Advanced Computing (SciDAC) research program—to speed up the modeling of all types of accelerators. Ongoing support of the capabilities developed in WarpX, and its wider ecosystem beyond the ECP project, will be vital to the research and development of future accelerators. According to Vay, the list of research areas that could benefit from WarpX is growing rapidly.

“It is already being used by our collaborators in the computational physics division to simulate the physics of pulsars,” he said.

There is also a spin-off of WarpX, called the Adaptive mesh Refinement Time-domain ElectrodynaMIcs Solver), or ARTEMIS, he noted, which couples the Maxwell’s equations implementation in WarpX with classical equations to simulate the behavior of quantum materials behavior and could lead to next-generation microelectronics.

ATAP researchers are working with AMReX to build a software stack called Beam, Plasma & Accelerator Simulation Toolkit (BLAST) comprising flexible modules that can be used for different applications, said Huebl. “Some of these modules, for example, are now leveraged in the ImpactX project.” The project is part of the Laboratory Directed Research and Development program and aims to improve the performance of linear accelerators and accelerator rings.

The team plans to investigate how WarpX could be used in simulations involving 20 to 50 consecutive laser plasma accelerators stages. The work will aim to create better electron beams for applications in radiotherapy and the new colliders.

“We also are also looking to extend the method beyond laser plasma accelerators to investigate ion acceleration and solid target interaction, for example, as used in fusion research,” said Rémi Lehe, a researcher at Berkeley Lab and a co-author of the Gordon Bell Prize winning paper.

Mesh refinement, he continued, would be “extremely useful not only in conventional accelerators but also in nuclear fusion technologies,” which is a key area of research for the DOE and “for which WarpX is also well positioned.”

The paper’s other co-authors include France Boillod-Cerneux, deputy at the CEA’s Fundamental Research Department regarding numerical simulations; Thomas Clark, a Ph.D. student at CEA; Kevin Gott, a NERSC staff member working in the User Engagement Group; Conrad Hillairet, with ARM; Stephan Jaure, with Atos; Adrien Leblanc, with ENSTA Paris; Myers, a member of the Center for Computational Sciences and Engineering at Berkeley Lab; Christelle Piechurski, the Chief HPC project officer for GENCI; Mitsuhisa Sato, deputy director of RIKEN Center for Computational Science; Neil Zaïm, a postdoc at CEA; and Weiqun Zhang, a senior computer systems engineer at Berkeley Lab.

To explore further…

• Berkeley Lab’s Physical Sciences Area has published a news article on the achievement.
• Read the technical paper on the prizewinning work.
• The Exascale Computing Project podcast Let’s Talk Exascale devoted a recent episode to WarpX, interviewing Vay, Huebl, Vincenti, and Fedeli.

Soren Prestemon

Soren Prestemon

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

Prestemon says as DPB Vice-Chair, he will work “to support the advancement of the field, work to enhance the broader communities’ recognition of its importance to society, and support a strong educational foundation to foster the next generation of physicists and engineers who can rapidly advance the field.”

“Advancing this field can open new windows into the fundamental nature of the universe and can support society in innumerable ways, from medical therapy to energy and environment solutions,” he says.

Marlene Turner

Marlene Turner

A research scientist in ATAP, Marlene Turner works on high-energy electron acceleration in laser-driven plasma wakefields and the next generation of particle colliders.

“I am honored to be part of the APS DPB,” she says, “and am excited to help reinforce and continue to enable strong scientific communication within the community by, for example, helping with the organization of conferences or the writing of the DPB newsletter and adapting them to meet the challenges of the current environment.”

Earlier this year, Turner was also one of three Berkeley Lab scientists selected by the U.S. Department of Energy’s Office of Science to receive funding through the Early Career Research Program (ECRP). Her ECRP project, “Energy Recycling for a Green Plasma Based Collider,” seeks to develop a path toward significantly decreasing future colliders’ energy consumption and operating costs.

“I understand how important passionate engagement of early-career scientists is for the future of our field, and I would work to ensure that we are diversely represented, given the right opportunities to grow, and included in important processes,” she says.

Cameron Geddes

Cameron Geddes

Geddes leads a wide range of plasma and related activities and collaborations, from accelerator physics to high energy density science to low-temperature plasmas and quantum information science, as well as supporting technologies such as superconducting magnets, exascale simulations, and lasers and diagnostics.

“This an exciting time for plasma physics, with renewed interest in fusion both public and private, a new understanding of fundamental processes and how they shape the cosmos, and the emergence of new accelerators and low-temperature plasma methods with strong social applications,” he says. The DPP appointment, says Geddes, will allow him “to further ATAPs role in planning and communication with funding agencies and the scientific world, and to ensure that our whole community has opportunities to contribute.”

The DPP’s meetings and activities will be “crucial in helping us learn from each other’s subareas and build a strong plasma physics field,” he says, adding that he “will strive to adapt the DPP’s programs to expand access, especially for early career researchers and others facing challenges participating, while looking for ways to build the personal connections that are a key part of meetings.”

Geddes also acknowledged the vital role that the APS plays “in growing our field into a more diverse population, which is crucial both to equity and to scientific progress.”

Empowerment in STEM Day: Friday, January 20, 2023

On Friday, January 20, 2023, the Women’s Support and Empowerment Council (WSEC) and K-12 Programs will host an Empowerment in STEM Day at Berkeley Lab.

This one-day event for public high school students will provide an opportunity to see Berkeley Lab up close, learn about summer opportunities, and speak directly to Berkeley Lab employees. This is an exciting opportunity to speak with students as they are deciding for themselves what it means to be a STEM and/or STEM adjacent professional.

Organizers of Empowerment in STEM Day are seeking volunteers from all genders and all STEM and STEM-adjacent Lab positions. Available opportunities include Job Shadow Host, Speed Networking Host, and Lunch Chats with Students participant.

Science en Acción (SeA) Bilingual STEM Camp

Berkeley Lab K-12 is seeking volunteers for Science en Acción (SeA), a spring break camp (April 5-8, 2023) for English learning/Spanish-English bilingual students who are interested in learning more about STEM and career opportunities at Berkeley Lab. Activities include tours of Berkeley Lab facilities, career talks with scientists, and workshops at Berkeley Lab and UC Berkeley. These events will be in English and Spanish.

A wide range of volunteer slots are available throughout the duration of camp, including document translators, workshop facilitators and workshop translators, application readers, and volunteers to meet and greet students/families as part of the welcoming committee.

Volunteers from all careers at Berkeley Lab are welcome, and there are roles for those who do not know Spanish.