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Proceedings ArticleDOI

Study of the Radiation Field From a Hollow Electron Beam Inside an Infrared Free Electron Laser Oscillator

28 Aug 2022-pp 1-2
TL;DR: In this article , the authors considered the operation of an IR free electron laser (FEL) oscillator with a hollow beam and analyzed its effect on FEL performance, and showed that using a hollow electron beam could offer a higher saturated power than use of a Gaussian electron beam.
Abstract: At University of Science and Technology of China, we have an Infrared (IR) free electron laser (FEL) oscillator experimental facility (FELiChEM) to generate radiations in the wavelength range of 2.5-50 m and 40-200 m. The output power is one of the most concerned parameters by the users. Since the electron beam distribution and the out-coupling hole in the resonator mirror can influence the saturated power and the optical mode, it would be an important issue to the output power of the IR light source. It has been demonstrated that use of a hollow electron beam could offer a higher saturated power than use of a Gaussian electron beam. Thus we consider the operation of FELiChEM with a hollow beam, and analyze its effect on FEL performance.
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Journal ArticleDOI
TL;DR: In this paper, the performance of free-electron laser (FELs) in the oscillator configuration, using a hollow electron beam distribution instead of the usual Gaussian, was investigated.
Abstract: We consider the performance of free-electron lasers (FELs) in the oscillator configuration, using a hollow electron beam distribution instead of the usual Gaussian. Using the three-dimensional, time-dependent FEL code genesis, we show that for FEL oscillators lasing can be achieved over a much broader range of cavity configurations with a hollow electron beam. This occurs because with the hollow electron beam higher-order optical modes and mode competition are suppressed. We also find a substantial increase in the saturated out-coupled power, with the optical mode still remaining the fundamental ${\mathrm{TEM}}_{00}$ mode. For a hollow electron beam, even with a finite mirror misalignment the transverse optical mode profile remains close to a ${\mathrm{TEM}}_{00}$ mode but with higher out-coupled power than with perfectly aligned mirrors. Thus, it is preferable to operate FEL oscillators with a hollow electron beam rather than a Gaussian.

4 citations

Journal ArticleDOI
TL;DR: In this paper , the authors combine theoretical analysis and numerical simulation to study the waveguide effect in the far-infrared oscillator for different waveguide sizes, and the results show that, with a waveguide of 30 mm × 10 mm initially used, a spectral gap will be found at 89 μ m and the FEL power at the wavelength longer than 100 μ m will be rather low.
Abstract: The FELiChEM infrared free-electron laser consists of two oscillators : the mid-infrared oscillator and the far-infrared oscillator, covering the spectral range of 2– 40 μ m and 20– 200 μ m , respectively. The mid-infrared oscillator finished the commissioning in 2020 and a deep spectral gap around the wavelength of 21 μ m existed. In this paper, combining theoretical analysis and numerical simulation, the research on this waveguide effect has been carried out and the simulation results highly agree with the measurement. Through using the same method, we study the waveguide effect in the far-infrared oscillator for different waveguide sizes. The results show that, with the waveguide of 30 mm × 10 mm initially used, a spectral gap will be found at 89 μ m and the FEL power at the wavelength longer than 100 μ m will be rather low. Based on these studies, a reasonable waveguide size of 30 mm × 16 mm has been reselected to make the tunable range of the far-infrared oscillator covering 20– 200 μ m . The recent measurement carried out in 2021 also agree with the prediction of the simulation results.

3 citations