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Electron Accelerators: How CERN is Driving Their Use Within and Beyond Physics

By Amedeo Habsburg

Hidden next to the PS, the CERN Linear Electron Accelerator for Research (CLEAR) is running a unique experimental facility, designed to explore and advance accelerator technologies with a wide range of scientific and industrial applications. Operational since 2017, CLEAR builds on the legacy of the former CTF3 (CLIC Test Facility 3), offering researchers a flexible and highly adaptable test-bed for research applications in a range of fields, including radiobiology and medicine.

In the 42 m accelerator hall, CLEAR produces short, intense electron bunches with energies up to 220 MeV. The accelerator is used for a variety of studies, including accelerator beam instrumentation, medical and biological research, dosimetry and detectors, and novel acceleration techniques. One of its key advantages is its modular setup, which allows scientists to reconfigure the beamline and easily test components in realistic, high-energy conditions.

Current and past experiments at CLEAR include the development of high-gradient accelerating structures, tests of electronics for radiation resistance (such as those bound for space), and the study of the use of electron beams for medical applications. CLEAR has also supported projects involving dosimetry systems, beam diagnostics, and machine learning research.

Importantly for this newsletter, CLEAR plays an impactful role in advancing medical research, particularly in the field of radiotherapy. It provides a controlled environment to test Very High Energy Electron (VHEE) beams for applications like FLASH radiotherapy, a promising technique in which Ultra High Dose Rates (UHDR) are delivered to patients in extremely short pulses, potentially minimizing damage to healthy tissue while effectively treating deep-seated tumors. FLASH was observed for the first time in 2014 when mice tumors were irradiated with short pulses (≤500 ms) at UHDR (≥40 Gy/s) with low energy electrons [1].

In the world of radiotherapy, FLASH is a game-changing technology. The mechanisms of the FLASH biological effects are being extensively studied, including at CLEAR, in order to better understand its workings, further optimize beam conditions to trigger the effect and validate the technologies needed for its translation to clinical practice.

As an enabler of fundamental and medical research, among others, CLEAR helps reduce the time from concept to implementation for new technologies, by providing a flexible environment to validate ideas in practice. For this reason, CLEAR has been extended with another 5 year mandate, approved in the Mid-Term Plan this year. Stay tuned to hear very soon, how their next years of research will aim to influence accelerator applications and impact society.

Find more about CLEAR here: https://home.cern/science/accelerators/clear, https://clear.cern/