Berkeley Lab

Leemans Laser Legacy (full version)


—Wim Leemans to move to DESY, lead Accelerator Division there

Advanced Accelerator R&D Pioneer Leaves a Laser Legacy at the Lab

By Glenn Roberts Jr., LBNL Strategic Communications, and Joe Chew, Accelerator Technology & Applied Physics Division

Wim LeemansATAP Division Director Wim Leemans — who built up Berkeley Lab’s laser-accelerator program from a modest office in a modular trailer into a world-class center for advanced accelerator R&D — is leaving the Lab after 27 years.

On Feb. 1, 2019, Leemans will take on a new role as director of the Accelerator Division at DESY in Hamburg, Germany. He will be responsible for the operation of the FLASH and XFEL free-electron lasers, the PETRA III light source, and the stewardship of a diverse Advanced Accelerator R&D program.

“DESY is one of the leading accelerator laboratories in the world,” noted Laboratory Director Mike Witherell. “This is an exceptional opportunity for Wim to apply his leadership skills to a major accelerator complex, encompassing all aspects of the field, including R&D, construction, and machine operations.”

Helmut Dosch, chairman of the DESY Board of Directors, said, “Wim Leemans is not only one of the most prominent leaders in accelerator research, but also a luminary in the development of pioneering laser plasma accelerators. We are proud and happy to have his creative spirit on board at DESY.”

Leemans, a native of Belgium, earned his Ph.D. in electrical engineering under Chan Joshi at the University of California, Los Angeles, and then joined Berkeley Lab in 1991 as a scientist in the Exploratory Studies Group, led by Swapan Chattopadhyay and Kwang-Je Kim, of the Accelerator and Fusion Research Division. Working with then-Lab Director Chuck Shank and others, Leemans developed a novel technique to produce ultrafast X-ray bunches by backscattering of an infrared laser off the ALS injector linac’s intense electron beam.

In 1994, he received a Laboratory Directed Research and Development award to start a program in laser-plasma acceleration, a new technology on which he had done his PhD dissertation during his time at UCLA.

 4.2 GeV laser capillary
BELLA holds the LPA energy record at 4.2 GeV, and a campaign toward 10 GeV is in progress.
“The breadth and depth of accomplishment of Wim’s program over the next 25 years were truly remarkable,” said Associate Laboratory Director for Physical Sciences James Symons. “Wim and his colleagues in the BELLA Center achieved many ‘firsts’ in laser- plasma acceleration: the first GeV electron beam, a world record acceleration of 4.2 GeV electrons in a single stage using the BELLA laser, and the demonstration of multiple-stage acceleration.”

“Wim has consistently been a strong advocate for the magnet program and for strong ties between ATAP and Engineering,” noted Soren Prestemon, who leads both the interdivisional Berkeley Center for Magnet Technology and the multi-institutional, Berkeley Lab-headquartered U.S. Magnet Development Program and has served as ATAP’s division deputy for technology.

Along the way, recognition for Wim’s work included the Department of Energy’s Ernest O. Lawrence Award, the American Physical Society’s J.M. Dawson Award for Excellence in Plasma Physics Research, the DOE Secretary’s Achievement Award for management of the BELLA Project, and the IEEE Particle Accelerator Science and Technology Award. He is a Fellow of the APS, the American Association for the Advancement of Science (AAAS), and the Institute of Electrical and Electronics Engineers (IEEE).

In addition to leading the BELLA Center, he has been the Director of the Accelerator Technology and Applied Physics Division since 2014. The renaming of the former Accelerator and Fusion Research Division reflected the broadening contributions of accelerators and related technologies to today’s science and technology challenges, while recognizing the core mission of the Division.

At DESY, Wim will be responsible for the operation of the FLASH and XFEL free- electron lasers, the PETRA III light source, and the stewardship of a diverse Advanced Accelerator R&D program. “I am sad to leave Berkeley Lab and especially my friends at BELLA Center after so many exciting years together,” he said, “but I am confident that the team is well-prepared to move ahead under new leadership, and I am looking forward to the challenges of my new position in Hamburg.”

Witherell said, “We are grateful for Wim’s lasting contributions to laser and accelerator science here, and look forward to continuing our work with him in ongoing and new collaborations with DESY.”

Toward new horizons for ATAP

Symons has designated Thomas Schenkel, ATAP Division Deputy for Technology and Head of the Fusion Science and Ion Beam Technology Program, to lead ATAP on an interim basis during the search for a permanent Division Director.

“There was something about this place – an energy here”

A hands-on experimentalist with a knack for resourcefulness, Leemans knew his calling as a scientist from a young age, when he transformed an attic space at his home among beet farms outside of Brussels, Belgium, into a lab and workshop, complete with a fume hood.

“I’ve always been a builder, even as a child,” Leemans said. This early start progressed into serious collegiate study. Irina Veretennicoff, a professor at Vrije Universeiteit Brussel, suggested that he follow his interest in plasma physics to the University of California, Los Angeles (UCLA).

There, under the mentorship of Professor Chan Joshi, Leemans learned about plasma-based acceleration techniques. Such techniques represent a new way to propel particles to incredible speeds over short distances, and have the potential to shrink the size and cost of large-scale accelerators.

Those were very early days for that acceleration paradigm (the concept had been proposed by Toshiki Tajima and John Myrick Dawson only a few years earlier, in 1979) and for Joshi’s lab. “I learned there how to make parts in the machine shop,” he said. Leemans received his master’s and Ph.D. degrees in electrical engineering at UCLA, and his Ph.D. dissertation work with carbon dioxide lasers helped win him a job at Berkeley Lab.

“I still remember my interview with Swapan Chattopadhyay and Kwang-Je Kim here in April 1991,” he said. “There was something about this place — an energy here.”

The Lab was seeking laser expertise for a proposed Chemical Dynamics Research Laboratory that would have been based on a free-electron laser, or FEL. To help prepare for this project, Leemans conducted experiments using an early FEL built at Stanford University.

At the time, the Advanced Light Source (ALS) was under construction at Berkeley Lab. Leemans worked with Shank, Robert Schoenlein and others on a Beam Test Facility that used intense beams from the ALS injector linac for a variety of experiments, including Thomson scattering. By aiming an infrared laser across the path of the electron beam, Leemans and others produced the first directed beams of hard-X-ray pulses lasting just hundreds of femtoseconds.

“I also wanted to get back into laser-plasma acceleration,” Leemans said. After winning approval for a Laboratory Directed Research and Development grant, he began to expand his lab space into areas that had previously been occupied by the SuperHILAC accelerator (which had been decommissioned in 1993) and the experimental facilities that had used its beams.

“There was a whole complex of ‘caves’ associated with the SuperHILAC, and there were magnets and cables everywhere,” Leemans said of moving into a space that was designed for a heavy-ion linear accelerator, which had been in operation since the late 1950s.


“Never bet against creativity. If you put smart people on a problem, they will come up with solutions”

When William Barletta came to Berkeley Lab in 1994 to serve as the Division Director, he further encouraged and supported these interests (and recognized Leemans’s knack for not only performing research but explaining the work and its significance). Leemans established Berkeley Lab’s Lasers, Optics, and Accelerator Systems Integrated Studies Program (LOASIS) in 1995; that program would evolve into the Berkeley Lab Laser Accelerator (BELLA) Center.

He helped to build a series of lasers (including one called Chihuahua, in a whimsical departure from the usually formidable names of high-power lasers, as well as Godzilla and TREX), which have all played roles in laser-driven plasma acceleration R&D at Berkeley Lab. Successes in experiments involving those lasers paved the way for the Lab’s BELLA laser, built with the help of American Recovery and Reinvestment Act stimulus funding.

Leemans with graduate students Joost Daniels (l.) and Kelly Swanson, ca. 2016
Leemans with graduate students Joost Daniels (l.) and Kelly Swanson, ca. 2016
“We started from scratch in the laser-plasma-acceleration field to become a world leader,” Leemans said. “We’ve mentored and hired and trained really top-notch people.” Leemans has served as BELLA Center director since 2009, growing it to some 30 people, and as ATAP Director since 2014. In a point of particular pride, he has served as a research advisor for more than 15 Ph.D. students. Laser-plasma acceleration and the BELLA facility were mentioned in the scientific background document for the 2018 Nobel Prize in Physics.

Today’s BELLA Center Center is a far cry from Leemans’ early days at Berkeley Lab, when he hung fliers in hallways on the University of California, Berkeley campus to find a research assistant.

“The first time we filled an upstairs room with (bare laser benches), a tech was with me. I was sitting on a bench and thinking, ‘How are we ever going to fill this whole lab?’ We filled up three-quarters of the building since then,” Leemans said. “It’s been quite a ride,” he added, with progress from electron beam energies of 200 MeV in 2004 to 1 GeV in 2006, then, with the BELLA laser, the current record of 4.2 GeV in 2014.

BELLA is now in a campaign toward 10 GeV, and has demonstrated coupling of one acceleration stage into another, a key technique for reaching high energies. Meanwhile ATAP researchers have been exploring several spinoff applications (such as an FEL; the ion-producing BELLA-i; and a Thomson-scattering source of monoenergetic gamma rays for nuclear security) and working to define next-generation high-intensity, high-average-power laser technologies that could drive future laser-plasma accelerators.

“It’s been a pleasure to work alongside Wim for these past 20 years,” said Eric Esarey, Senior Science Advisor for the ATAP Division and Deputy Head of the BELLA Center. “Helping to grow the center from just a few researchers when I joined Berkeley Lab in 1998 to a great team of over two dozen outstanding researchers has been very rewarding. It’s also been fascinating to see the laser technology evolve from an in-house-built multi-terawatt system in the late ’90s to the state-of-the-art petawatt system that we currently run.”

“I have definitely learned a great deal from Wim over the years and he has been an exceptional leader,” added Esarey. “I look forward to fruitful collaborations when he is at his new home in DESY.”

Leemans noted how there have been some twists and turns while pursuing high-energy laser-driven plasma acceleration, and solutions have been found that reversed some skeptics’ doubts.

“Never bet against creativity,” he said. “If you put smart people on a problem, you will come up with solutions.”

ATAP Division: a learning organization changes with the times
ATAP has been transformed under Leemans’s leadership, right down to the name. What had been the Accelerator and Fusion Research Division since the late ’70s was renamed in 2014 to better reflect the broadening contributions of accelerators and related technologies to today’s science and technology challenges while recognizing the core mission of the division.

The Center for Beam Physics (formerly the Exploratory Studies Group) gave rise to an Accelerator Modeling Program that takes advantage of the unique local synergy of accelerator and plasma simulation, computational research, and supercomputing. The experimental expertise of the Center for Beam Physics was refocused into the Berkeley Accelerator Controls and Instrumentation Program (BACI).

Additionally, in a pair of related efforts that have flourished in recent years, the Berkeley Center for Magnet Technology (BCMT) brought together the already intertwined ATAP and Engineering Division efforts on advanced magnets, and a multi-institutional U.S. Magnet Development Program (USMDP) was founded by DOE Office of High Energy Physics to pursue high-field accelerator magnet technology, with Berkeley Lab as the lead laboratory.

ATAP’s R&D programs, DOE projects, and business context continued to increase in complexity, addressed with the new position of Division Deputy, Operations. Asmita Patel, trained as a scientist, also brought an MBA and over 20 years of financial management, communications, and strategic-planning experience to this new position. “Wim saw that a unified operations team and a focus on efficiency and process streamlining had become a wise investment,” Patel observed.

These changes and strategies are aligned with agency and community needs and priorities. Notable high-level guidance included Building for Discovery: Strategic Plan for U.S. Particle Physics in the Global Context (the “P5 Report”) and Accelerating Discovery: A Strategic Plan for Accelerator R&D in the U.S. This strategic guidance has informed everything ATAP does, from the charter of the US-MDP to the roadmap toward k-BELLA, a next-level laser-plasma accelerator named for the kilohertz repetition rate / kilowatt average power of its laser.

Prestemon observed, “Wim has been a strong leader of ATAP’s strategic planning processes and of showing our agency stakeholders that we understand and respond to their needs.” The benefits are intramural as well; he added that “Wim has made sure that all stakeholders, the funding agencies and our own staff understand and embrace the vision of what we’re doing and the overall goals of our work. He has been an exemplar and mentor to me in defining and articulating our strategy.”

Seeking guidance from the scientific community through workshops has also emerged as a key part of ATAP’s decision-making processes. Recent workshops and panels have examined and re-defined the prospects for medical accelerators, surveyed potential laser technologies for k-BELLA and beyond; looked at the science that could be enabled by ion beams from BELLA-i, and prioritized fusion-energy-related research opportunities for quantum information systems — a fast-moving field with a very strong and growing Berkeley Lab presence in which ATAP programs also play a role.

The DOE Big Ideas Summit inspired us to bring together user and source experts to further our emphasis on “bringing the accelerator to the application,” and the Berkeley Lab Accelerator Simulation Toolkit effort recently held the first-ever meeting of its diverse user community. These planning processes continue; most recently, Thomas Schenkel, named as interim director of ATAP, co-chaired the Fusion Energy Sciences Roundtable on Quantum Information Sciences.

Schenkel’s own technical background in ion-beam science and applications has led him to closely work with Leemans on the BELLA-i initiative, which has expanded the science scope of BELLA: high-energy-density science and the acceleration of ions have been added to BELLA’s central mission in advanced accelerator science for high-energy physics with electrons. Schenkel also has a long history of working on enabling technologies for quantum information systems, which have now emerged as a Labwide emphasis. Having worked closely with Leemans as Division Deputy for Technology, Schenkel acknowledged a debt of gratitude to Wim for his executive skills and his deep scientific expertise.

“I’ve very much enjoyed our time working together on the BELLA-i initiative – from early ideas through proposals, and now with our first science results and new funding. It’s one example of the process of innovation and the manifestation of opportunities that we strive for in ATAP and Berkeley Lab.”

Back to the December 2018 ATAP Newsletter