Energy recovery linacs (ERLs) possess bright prospect of the fully coherent x-ray generation. Recently, we designed a 600 MeV energy recovery linac capable of producing high power fully coherent radiation pulses at 13.5 nm with a relatively low-intensity 256.5 nm seed laser profited from the employment of angular-dispersion-induced microbunching (ADM) technology. We also designed a matched multiplexed system that can deflect each radiator by 8 mrad with a carefully choreographed multi-bend achromat (MBA) scheme. As a result of downstream MBA’s dispersion compensation, bunching factors will be enhanced both at fundamental wavelength and high harmonics. The bunching factor of the 19th harmonic increased from 10% to 26%, and that of the 57th harmonic became 7.8%, which is sufficient to generate fully coherent radiation in the soft X-ray range.

Free-electron lasers (FEL) producing ultra-short X-ray pulses with high brightness and continuously tunable wavelength have been playing an indispensable role in the field of materials, energy catalysis, biomedicine, and atomic physics. A core challenge is to maintain and improve the transverse overlap of the electron and laser beams. This requires high-dimensional, high-frequency, closed-loop control with magnetic elements, further complicated by the diverse requirements across a wide range of wavelength configurations. In this work, we introduce a proximal policy optimization architecture for FEL commissioning that autonomously learns to control the set of magnetic elements. We experimentally demonstrated the feasibility of this technique on the alignment of electron beams and laser beams automatically in Shanghai Soft X-Ray Free Electron Laser User Facility, by adjusting groups of corrector magnets to maximize the FEL output power.

Free-electron lasers (FEL) producing ultra-short X-ray pulses with high brightness and continuously tunable wavelength have been playing an indispensable role in the field of materials, energy catalysis, biomedicine, and atomic physics. A core challenge is to maintain and improve the transverse overlap of the electron and laser beams. This requires high-dimensional, high-frequency, closed-loop control with magnetic elements, further complicated by the diverse requirements across a wide range of wavelength configurations. In this work, we introduce a proximal policy optimization architecture for FEL commissioning that autonomously learns to control the set of magnetic elements. We experimentally demonstrated the feasibility of this technique on the alignment of electron beams and laser beams automatically in Shanghai Soft X-Ray Free Electron Laser User Facility, by adjusting groups of corrector magnets to maximize the FEL output power.

Energy recovery linacs (ERLs) possess bright prospect of the fully coherent x-ray generation. Recently, we designed a 600 MeV energy recovery linac capable of producing high power fully coherent radiation pulses at 13.5 nm with a relatively low-intensity 256.5 nm seed laser profited from the employment of angular-dispersion-induced microbunching (ADM) technology. We also designed a matched multiplexed system that can deflect each radiator by 8 mrad with a carefully choreographed multi-bend achromat (MBA) scheme. As a result of downstream MBA’s dispersion compensation, bunching factors will be enhanced both at fundamental wavelength and high harmonics. The bunching factor of the 19th harmonic increased from 10% to 26%, and that of the 57th harmonic became 7.8%, which is sufficient to generate fully coherent radiation in the soft X-ray range.