Redshift and harmonic radiation of nonlinear Laser-Thomson scattered X-rays


Redshift and harmonic radiation of nonlinear Laser-Thomson scattered X-rays

Krämer, J. M.; Irman, A.; Jochmann, A.; Pausch, R.; Debus, A.; Couperus, J. P.; Köhler, A.; Zarini, O.; Kuntzsch, M.; Budde, M.; Lehnert, U.; Wagner, A.; Bussmann, M.; Cowan, T.; Schramm, U.

Thomson scattering of intense laser pulses from relativistic electrons not only allows for the generation of bright x-ray pulses but also serves as a laboratory for strong field physics and nonlinear interactions. We present high resolution angle and energy resolved characterization of laser-Thomson scattered X-rays generated by colliding picosecond electron bunches from the superconducting ELBE linear accelerator with counter-propagating laser pulses from the 150 TW DRACO Ti:Sapphire laser system.
The measurements quantify the influence of the two major interaction parameters, namely laser intensity and electron beam emittance, on the spectral bandwidth of the scattered photons. The experimental range of normalized laser intensities (a0 from 0.15 to 1.7) covers the transition region from the linear to the nonlinear regime of the Thomson scattering interaction. In this parameter scan, we record and spectrally resolve the increasing redshift and broadening of the fundamental of the radiation, the rise of hamonics as well as the gain in total photon flux.
In the second study, we vary the interaction geometry, which allows for selecting only parts of the electron bunch to interact with the laser. By this means, we control the ensemble of interaction angles which is measured by the effective emittance of the electron beam. The bandwidth of the Thomson spectrum increases with the effective emittance, which can be used as a tuning knob for shaping the Thomson spectrum.
Numerical simulations of both studies performed with the classical radiation solver CLARA show good agreement, benchmarking this code with the experiments.

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Publ.-Id: 25534