Abstract
The mid-infrared range is an important spectrum range where materials exhibit a characteristic response corresponding to their molecular structure. A free-electron laser (FEL) is a promising candidate for a high-power light source with wavelength tunability to investigate the nonlinear response of materials. Although the self-amplification spontaneous emission (SASE) scheme is not usually adopted in the mid-infrared wavelength range, it may have advantages such as layout simplicity, the possibility of producing a single pulse, and scalability to a short-wavelength facility. To demonstrate the operation of a mid-infrared SASE FEL system in an energy recovery linac (ERL) layout, we constructed an SASE FEL setup in cERL, a test facility of the superconducting linac with the ERL configuration. Despite the adverse circumstance of space charge effects due to the given boundary condition of the facility, we successfully established the beam condition at the undulators and observed FEL emission at a wavelength of 20 μm. The results show that the layout of cERL has the potential for serving as a mid-infrared light source.
Highlights
Human society depends on various materials, which are being further developed by game-changing innovations in the production of useful materials
In the mid-infrared spectrum range, which is defined as 3–50 μm in wavelength, materials exhibit a characteristic response corresponding to their molecular structure
Despite the adverse circumstance that the beam quality was strongly affected by space charge effects, we developed a procedure to transport the beam in a controlled manner to the exit of the free-electron laser (FEL) layout
Summary
Human society depends on various materials, which are being further developed by game-changing innovations in the production of useful materials. A widely used light source in the mid-infrared range has been the CO2 laser.7 It can produce several 10 kW of power, the wavelength is fixed at 10.6 μm. Scitation.org/journal/rsi serve as a compact light source and is expected to be used widely It can produce 1 W of power in continuous operation in the ∼8 μm wavelength range.. A sub-femto second x-ray FEL has been required for the investigation of fast electron dynamics within atoms and molecules In such a regime, the slippage effect becomes important even at short wavelengths. The slippage effect becomes important even at short wavelengths In such a short-pulse x-ray FEL, it has been recognized that the undulator tapering scheme is effective in optimizing the efficiency of interaction between the radiation and the electron beam in the time slippage..
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