Andrea Hannasch, UT-Austin

"Generation, measurement, and application of x-rays from laser-plasma electron accelerators"

Abstract: Laser-plasma electron accelerators are compact sources of x-rays with comparable brightness to conventional RF accelerator light sources at a fraction of the cost and size. X-rays can be generated in 3 main ways from laser-plasma accelerators including: 1) betatron oscillations of the electrons while still accelerating; 2) inverse Compton scatter (ICS) x-rays in which electrons oscillate in the electric field of a counter-propagating laser pulse after exiting the accelerator; 3) bremsstrahlung from the impact of accelerated electrons with a solid target. These secondary x-rays span several orders of magnitude in energy and can be broadband (betatron and bremsstrahlung) or relatively narrowband (ICS), making them extremely versatile sources for applications in smaller university labs. This talk presents a comprehensive study of the generation mechanisms, diagnostic techniques, and possible applications of few keV to 100 MeV x-rays generated by laser-plasma electron accelerators. First, x-rays generated at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) were spectrally unfolded, both individually and in mixtures, using a compact stack calorimeter made up of alternating layers of absorbing material and image plates. The x-ray energies observed during this campaign spanned from few-keV betatron x-rays, to ~1 MeV narrowband ICS x-rays, and to broadband bremsstrahlung with an average energy of ~30 MeV. This modular stack calorimeter can be easily redesigned for sensitivity to different energy ranges and was extended to diagnose high energy x-rays generated by The Texas Petawatt (TPW) Laser at The University of Texas with photon energies well over 100 MeV. Additional characterization was performed at HZDR to explore the capabilities and limitations of a LPA and plasma mirror combo to generate ICS x-rays in both a linear and nonlinear regime.