Above: Assistant Professors Siqi Li (left) and Niels Bidault installing a cathode in the electron gun and checking its alignment
DEEP WITHIN THE CONCRETE VAULTS OF WATANABE HALL on the University of Hawai‘i at Mānoa (UH Mānoa) campus, an ambitious scientific renaissance is underway. What once sat dormant for nearly a decade— a powerful, highly specialized instrument known as a Free-Electron Laser (FEL)— is now sparking back to life, thanks to a new generation of accelerator physicists at UH Mānoa, determined to restore the FEL’s brilliance and redefine its potential.
Why the FEL Matters
Unlike conventional lasers, the FEL produces tunable light by accelerating electrons through alternating magnetic fields. This unique mechanism makes it a versatile tool, allowing researchers to probe matter at the molecular and atomic scale, making it a vital tool in physics and chemistry to biology and materials science.
At UH Mānoa, the FEL facility engages in:
- Biological research including studies on DNA damage and advanced cancer treatments like FLASH-Radiotherapy, which delivers ultra-short, high-dose radiation pulses that target tumors while minimizing side effects;
- Materials science research, analyzing how radiation affects everything from spacecraft materials and microelectronics to biological tissues;
- Nanostructure wake research, a new frontier in exploring how energy and information propagate at the nanoscale, potentially critical in transforming future electronics and sensor technologies;
- Fundamental physics in studying particle interactions, synchrotron radiation and investigating phenomena like Inverse Compton scattering— a process when fast-moving electrons collide with low-energy photons, producing high-energy radiation such as X-rays. With this capability, the lab can also help simulate and explore astrophysical phenomena, such as those involving extreme energy transfer near black holes and other cosmic environments; and
- Advanced light source development, including free-electron laser and Inverse Compton scattering in a controlled lab setting to create tunable, radiation beams. These sources are compact and versatile, with applications in imaging, materials research, and nuclear physics.
Since its invention, the FEL has enabled major breakthroughs in advancing scientific understanding, such as capturing ultrafast chemical reactions, determining the structure of complex proteins for drug development, and probing materials at the atomic scale to inform next-generation electronics and energy technologies.
The Legacy of John Madey
The FEL’s journey to Hawai‘i all began with the late John Madey, a pioneering physicist who invented the FEL in the 1970s, transforming high-energy light research. He first developed, demonstrated and patented his FEL technology while at Stanford University, and refined it at Duke University before bringing his FEL technology to UH Mānoa in 1998.
Over the years, his research and foundational work inspired and enabled the development of giant, half-billion-dollar class FEL machines operated at world-renowned labs including: the SLAC National Accelerator Laboratory (formerly the Stanford Linear Accelerator Center and better known as SLAC) in Stanford, CA; the Super Photon ring-8 synchrotron radiation facility in Japan’s Harima Science Park City; and the Deustches Elektronen-Synchrotron (DESY) research center in Hamburg, Germany.
Upon the FEL’s arrival at UH Mānoa, Madey oversaw the construction of a massive radiation-shielded bunker that enabled the FEL to become fully operational in the early 2000s, producing infrared light that led to successful observations of X-rays from Inverse Compton scattering. Unfortunately, the program stalled upon his passing in 2016, and the precision, interdisciplinary knowledge, and continuous maintenance required to operate the FEL became difficult to sustain, particularly during the COVID-19 pandemic.
Revival and Expansion
In 2024, UH Mānoa took a strategic leap forward by hiring two rising stars in accelerator physics: Assistant Professor Siqi Li from the SLAC, and Assistant Professor Niels Bidault from CERN, the European Organization for Nuclear Research in Switzerland. Their mission: restart the FEL, upgrade its capabilities, and carve a new path forward.
“Operating the FEL is like building a Swiss watch, but at the scale of a particle beam,” said Bidault. “It requires precision across every domain — electrical engineering, vacuum science, magnets, diagnostics, high-voltage systems. Everything must align within millimeters or less in order to work.”
Li and Bidault are working with a team of two postdocs and several undergraduate students on the following technology upgrades:
- Establishing Start-to-End Beam Simulations to build the framework for optimizing beam quality, diagnosing performance issues, and guiding future upgrades with predictive modeling;
- Cavity-Based FEL System to generate tunable bright infrared laser light that seeds the Inverse Compton scattering process to produce high-energy X-rays, which can be used for medical imaging, cancer treatment and other industrial applications; and
- Energy Recovery Linac (ERL) a significant functional upgrade that would recycle unused energy from the electron beam, increasing experimental time and energy efficiency.
In addition, Li is leading a nearly $1-million Department of Energy Established Program to Stimulate Competitive Research-funded project that develops a comprehensive simulation framework to fully understand FEL physics and combines traditional beam physics with cutting-edge machine learning techniques to optimize the FEL’s controls.
“There are thousands of parameters to tune in such a complicated system,” said Li. “Machine learning offers a way to achieve precision, stability and efficiency beyond what human operators can do alone.”
In collaboration with SLAC, Li’s team is developing algorithms that can intelligently adjust the accelerator’s operations to optimize beam performance and stability, making UH Mānoa’s FEL a cutting-edge testbed for utilizing artificial intelligence (AI) in experimental physics.
Training Tomorrow’s Innovators
Unlike in Europe, where accelerator science is well-established across multiple national universities, the U.S. has very few such academic programs. National labs like SLAC and Fermilab in Illinois rely heavily on a small talent pool that is growing in demand, which UH Mānoa is now helping to develop.
“This is a huge opportunity for students,” said Bidault. “They’re not just learning theory, they’re helping us tune the machine, run diagnostics, even simulate beam physics. It’s hands-on training with global consequences.”
The implications extend beyond academia. High-tech industries, medical imaging companies, and even aerospace sectors rely on beam physics and accelerator technology. UH’s training pipeline may soon become a vital contributor to the broader U.S. and international science and technology workforce.
Looking Toward the Future
After a recent visit to the lab, renowned physicist Vladimir Shiltsev, a former director at Fermilab, praised UH’s efforts to revive the FEL and suggested the university could become a national hub for accelerator science.
“The program will enable unique research across multiple disciplines, from high-energy and nuclear physics to advanced light sources and medical applications, and has the potential to position Hawai‘i as a globally recognized hub for accelerator science,” said Shiltsev.
With technical restoration nearly complete, Li and Bidault expect to produce their first new electron beams by fall 2025. Once operational, the lab will serve not only as a research powerhouse but also as a magnet for aspiring physicists, engineers and AI scientists across the Pacific and beyond.
As the UH FEL hums back to life, it symbolizes more than a restart. It marks the beginning of a new era of scientific discovery at the edge of light and matter.