Coherent X-ray source generation with off-resonance laser modulation

Abstract

The generation of ultrashort coherent radiation in the extreme-ultraviolet (EUV) and soft X-ray regimes is of great significance in a broad range of research. In this paper, a promising scheme for generating coherent harmonic radiation using off-resonance seed laser modulation is discussed. The off-resonance seed laser, whose wavelength differs from the resonant wavelength of the undulator, is first used to modulate the angular distribution of the electron beam (e beam) in the undulator (modulator). After passing through a dispersion section, strong coherent micro-bunching is introduced into the e beam, which contains high-order harmonic components of the seed laser. Theoretical analysis and simulations indicate that this method can be used for the generation of coherent EUV and soft X-ray radiation at sub-gigawatt power in a meter-scale undulator (radiator).

A coherent harmonic generation method for producing femtosecond coherent radiation in a laser plasma accelerator based light source

“…This form does not only apply to the energy modulation method but also to angular modulation methods (Yu, 1991;Xiang & Wan, 2010). In the next section, we will compare the proposed method with the angular modulation methods proposed by Feng et al (2015) and Feng et al (2018), based on this formula. According to the property of the Bessel function, the nthorder (n > 4) Bessel function reaches the first maximum ($ 0.67n À1/3 ) when its argument is equal to n + 0.81n 1/3 .…”

“…Stepping further, the forthcoming experiments may focus on coherent undulator radiation (Labat et al, 2020;Alotaibi et al, 2020). Some coherent harmonic generation (CHG) methods (Feng et al, 2015;Feng et al, 2018;Liu et al, 2019) have been proposed to achieve this goal. These CHG methods use a modulation beamline to generate microbunching structures in the electron bunch.…”

“…On the other hand, the angular modulation methods (Feng et al, 2015;Feng et al, 2018) use the seed laser to modulate the transverse angle (or divergence) of the electron beam. Then a dispersion section providing a coupling between the longitudinal position and transverse angle (instead of longitudinal dispersion) is employed to convert the angular modulation into density modulation.…”

“…Since the bunching factor of these methods is independent of the initial energy spread and the beam divergence, they can be used to generate high-power EUV or soft X-ray coherent radiation in an LPA-driven light source. To induce an angular modulation, a wavefront-tilted seed laser is adopted by Feng et al (2015); and Feng et al (2018) set the modulator resonant wavelength to the second harmonic of the seed laser (off-resonance condition).…”

Optimization of Electron Beams Based on Plasma-Density Modulation in a Laser-Driven Wakefield Accelerator

“…Laser-wakefield acceleration (LWFA) is an aspirational technology in the acceleration community for producing compact, bright, and highly relativistic e beams. These LWFAbased e beams can act as potential drivers of free-electron lasers (FELs) [1,2], sources of tabletop X-rays and Gamma-rays [3,4], and even candidates for healthcare [5,6]. High-quality e beams can be achieved with a variety of injection techniques, such as self-injection [7,8], ionization-induced injection [9][10][11][12], density down-ramp injection [13,14], or colliding-pulse injection [10,15].…”