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Superluminal sheath-field expansion and fast-electron-beam divergence measurements in laser-solid interactions.

Authors
  • Ridgers, C P
  • Sherlock, M
  • Evans, R G
  • Robinson, A P L
  • Kingham, R J
Type
Published Article
Journal
Physical Review E
Publisher
American Physical Society (APS)
Publication Date
Mar 01, 2011
Volume
83
Issue
3 Pt 2
Pages
36404–36404
Identifiers
PMID: 21517601
Source
Medline
License
Unknown

Abstract

We show that including a sufficient description of the target's rear surface significantly affects the interpretation of a wide range of laser-solid experiments. A simple Debye sheath model will be shown to be adequate. From this the sheath field responsible for ion acceleration has been shown to expand at superluminal speeds, leading to very large ion-emission regions on the target's rear surface; a new explanation for the dynamics of the ion-accelerating sheath field accounts for this observation and demonstrates the inaccuracy of measuring the angular divergence of the injected electron beam, crucial to fast ignition, from the lateral extent of the ion emission. However, it is shown that on careful probing the sheath field can provide unique insight into details of the fast electron's distribution function. The relative merits of probing other physical quantities has been examined. The width of the background temperature spot overestimates the divergence by a factor of 2 unless electron recirculation is prevented.

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