Bremsstrahlung and K alpha fluorescence measurements for inferring conversion efficiencies into fast ignition relevant hot electrons

The Bremsstrahlung and K-shell emission from 1×1×1 mm[superscript 3] planar targets irradiated by a short-pulse 3×10[superscript 18]–8×10[superscript 19] W/cm[superscript 2] laser were measured. The Bremsstrahlung was measured using a filter stack spectrometer with spectral discrimination up to 50...

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Bibliographic Details
Main Authors: Chen, C. D., Patel, P. K., Hey, D. S., Mackinnon, A. J., Key, M. H., Akli, K. U., Bartal, T., Beg, F. N., Chawla, S., Chen, H., Freeman, R. R., Higginson, D. P., Link, A., Ma, T. Y., MacPhee, A. G., Stephens, R. B., Van Woerkom, L. D., Westover, B., Porkolab, Miklos
Other Authors: Massachusetts Institute of Technology. Plasma Science and Fusion Center
Format: Article
Language:en_US
Published: American Institute of Physics 2010
Online Access:http://hdl.handle.net/1721.1/52297
https://orcid.org/0000-0002-9518-4097
Description
Summary:The Bremsstrahlung and K-shell emission from 1×1×1 mm[superscript 3] planar targets irradiated by a short-pulse 3×10[superscript 18]–8×10[superscript 19] W/cm[superscript 2] laser were measured. The Bremsstrahlung was measured using a filter stack spectrometer with spectral discrimination up to 500 keV. K-shell emission was measured using a single photon counting charge coupled device. From Monte Carlo modeling of the target emission, conversion efficiencies into 1–3 MeV electrons of 3%–12%, representing 20%–40% total conversion efficiencies, were inferred for intensities up to 8×10[superscript 19] W/cm[superscript 2]. Comparisons to scaling laws using synthetic energy spectra generated from the intensity distribution of the focal spot imply slope temperatures less than the ponderomotive potential of the laser. Resistive transport effects may result in potentials of a few hundred kV in the first few tens of microns in the target. This would lead to higher total conversion efficiencies than inferred from Monte Carlo modeling but lower conversion efficiencies into 1–3 MeV electrons.