Electron and X-ray source development using picosecond, kilojoule class laser systems




King, Paul M

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Self-modulated laser wakefield acceleration (SM-LWFA) of electrons, driven by picosecond, kilojoule class laser systems is a promising method to produce versatile x-ray sources. The electron beams, accelerated up to ≈300 MeV, are used to produce broadband (keV to MeV), low divergence (¡ 50 mrad), high photon number (>10¹⁰ photons/keV/sr) x-ray sources utilizing betatron, inverse Compton scattering, and bremsstrahlung generation mechanisms. The x-ray energy spectrum and source size can be tuned by controlling the SM-LWFA directly or the x-ray generation mechanism to provide an optimized source for radiography applications. We will discuss experimental results on electron beam and x-ray source characterization, obtained at the Jupiter Laser Facility (LLNL), and supported by 2D and 3D Particle-In-Cell simulations. Additionally, we will show several static radiography applications relevant to high energy density science and inertial confinement fusion experiments and how this source can be tuned to improve image quality in radiography. X-ray analysis tools have been developed to measure high energy x-ray spectra, source size, and radiography quality, and we have used LLNL’s x-ray ray tracing code HADES to simulate radiographic images of experimental objects and help in planning for future experiments and applications. Finally, MeV x-ray source characterization and radiography applications are explored using laser-solid interactions enhanced by compound parabolic concentrators (CPC). This work was performed under the auspices of the U.s. Department of Energy under Contract No. DE-AC52-07NA27344, DE-SC0019010, DE-SC0010064 (UCLA), DE-SC0021057, NNSA grant DE-NA0003873 (UCLA) and NSF grants 1806046, 1804463, 1734315, and 2003354 (UCLA), LLNL subcontract B634451, FA9550-14-1-0045, and supported by the DOE Office of Science Early Career Research Program (Fusion Energy Sciences) under SCW1575-1.



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