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Title: Initial experimental evidence of self-collimation of target-normal-sheath-accelerated proton beam in a stack of conducting foils

Phenomena consistent with self-collimation (or weak self-focusing) of laser target-normal-sheath-accelerated protons was experimentally observed for the first time, in a specially engineered structure (“lens”) consisting of a stack of 300 thin aluminum foils separated by 50 μm vacuum gaps. The experiments were carried out in a “passive environment,” i.e., no external fields applied, neutralization plasma or injection of secondary charged particles was imposed. Experiments were performed at the petawatt “PHELIX” laser user facility (E = 100 J, Δt = 400 fs, λ = 1062 nm) at the “Helmholtzzentrum für Schwerionenforschung–GSI” in Darmstadt, Germany. The observed rms beam spot reduction depends inversely on energy, with a focusing degree decreasing monotonically from 2 at 5.4 MeV to 1.5 at 18.7 MeV. The physics inside the lens is complex, resulting in a number of different mechanisms that can potentially affect the particle dynamics within the structure. We present a plausible simple interpretation of the experiment in which the combination of magnetic self-pinch forces generated by the beam current together with the simultaneous reduction of the repulsive electrostatic forces due to the foils are the dominant mechanisms responsible for the observed focusing/collimation. This focusing technique could be applied to a wide variety of space-chargemore » dominated proton and heavy ion beams and impact fields and applications, such as HEDP science, inertial confinement fusion in both fast ignition and heavy ion fusion approaches, compact laser-driven injectors for a Linear Accelerator (LINAC) or synchrotron, medical therapy, materials processing, etc.« less
Authors:
; ;  [1] ; ; ; ;  [2] ; ; ;  [3] ;  [4] ; ; ;  [5] ;  [6]
  1. Lawrence Berkeley National Laboratory, California 94720 (United States)
  2. Lawrence Livermore National Laboratory, California 94551 (United States)
  3. University of California, San Diego, California 92093 (United States)
  4. General Atomics, San Diego, California 92121 (United States)
  5. GSI-Darmstadt, Planckstraße 1, 64291 Darmstadt (Germany)
  6. TU-Darmstadt, Karolinenplatz 5, 64289 Darmstadt (Germany)
Publication Date:
OSTI Identifier:
22224201
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 20; Journal Issue: 8; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALUMINIUM; HEAVY IONS; LINEAR ACCELERATORS; PLASMA FOCUS; PLASMA GUNS; PLASMA PRODUCTION; PLASMA SHEATH; PROTON BEAMS; PROTONS; SYNCHROTRONS