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Title: Arc-based smoothing of ion beam intensity on targets

Abstract

By manipulating a set of ion beams upstream of a target, it is possible to arrange for a smoother deposition pattern, so as to achieve more uniform illumination of the target. A uniform energy deposition pattern is important for applications including ion-beam-driven high energy density physics and heavy-ion beam-driven inertial fusion energy ('heavy-ion fusion'). Here, we consider an approach to such smoothing that is based on rapidly 'wobbling' each of the beams back and forth along a short arc-shaped path, via oscillating fields applied upstream of the final pulse compression. In this technique, uniformity is achieved in the time-averaged sense; this is sufficient provided the beam oscillation timescale is short relative to the hydrodynamic timescale of the target implosion. This work builds on two earlier concepts: elliptical beams applied to a distributed-radiator target [D. A. Callahan and M. Tabak, Phys. Plasmas 7, 2083 (2000)] and beams that are wobbled so as to trace a number of full rotations around a circular or elliptical path [R. C. Arnold et al., Nucl. Instrum. Methods 199, 557 (1982)]. Here, we describe the arc-based smoothing approach and compare it to results obtainable using an elliptical-beam prescription. In particular, we assess the potential of thesemore » approaches for minimization of azimuthal asymmetry, for the case of a ring of beams arranged on a cone. It is found that, for small numbers of beams on the ring, the arc-based smoothing approach offers superior uniformity. In contrast with the full-rotation approach, arc-based smoothing remains usable when the geometry precludes wobbling the beams around a full circle, e.g., for the X-target [E. Henestroza, B. G. Logan, and L. J. Perkins, Phys. Plasmas 18, 032702 (2011)] and some classes of distributed-radiator targets.« less

Authors:
 [1]
  1. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States) and The Virtual National Laboratory for Heavy Ion Fusion Science (United States)
Publication Date:
OSTI Identifier:
22072490
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 19; Journal Issue: 6; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 43 PARTICLE ACCELERATORS; ASYMMETRY; DEPOSITION; ENERGY DENSITY; HEAVY IONS; ICF DEVICES; IMPLOSIONS; INERTIAL FUSION DRIVERS; ION BEAM TARGETS; ION BEAMS; OSCILLATIONS; RADIATORS; ROTATION

Citation Formats

Friedman, Alex. Arc-based smoothing of ion beam intensity on targets. United States: N. p., 2012. Web. doi:10.1063/1.4729841.
Friedman, Alex. Arc-based smoothing of ion beam intensity on targets. United States. https://doi.org/10.1063/1.4729841
Friedman, Alex. 2012. "Arc-based smoothing of ion beam intensity on targets". United States. https://doi.org/10.1063/1.4729841.
@article{osti_22072490,
title = {Arc-based smoothing of ion beam intensity on targets},
author = {Friedman, Alex},
abstractNote = {By manipulating a set of ion beams upstream of a target, it is possible to arrange for a smoother deposition pattern, so as to achieve more uniform illumination of the target. A uniform energy deposition pattern is important for applications including ion-beam-driven high energy density physics and heavy-ion beam-driven inertial fusion energy ('heavy-ion fusion'). Here, we consider an approach to such smoothing that is based on rapidly 'wobbling' each of the beams back and forth along a short arc-shaped path, via oscillating fields applied upstream of the final pulse compression. In this technique, uniformity is achieved in the time-averaged sense; this is sufficient provided the beam oscillation timescale is short relative to the hydrodynamic timescale of the target implosion. This work builds on two earlier concepts: elliptical beams applied to a distributed-radiator target [D. A. Callahan and M. Tabak, Phys. Plasmas 7, 2083 (2000)] and beams that are wobbled so as to trace a number of full rotations around a circular or elliptical path [R. C. Arnold et al., Nucl. Instrum. Methods 199, 557 (1982)]. Here, we describe the arc-based smoothing approach and compare it to results obtainable using an elliptical-beam prescription. In particular, we assess the potential of these approaches for minimization of azimuthal asymmetry, for the case of a ring of beams arranged on a cone. It is found that, for small numbers of beams on the ring, the arc-based smoothing approach offers superior uniformity. In contrast with the full-rotation approach, arc-based smoothing remains usable when the geometry precludes wobbling the beams around a full circle, e.g., for the X-target [E. Henestroza, B. G. Logan, and L. J. Perkins, Phys. Plasmas 18, 032702 (2011)] and some classes of distributed-radiator targets.},
doi = {10.1063/1.4729841},
url = {https://www.osti.gov/biblio/22072490}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 6,
volume = 19,
place = {United States},
year = {Fri Jun 15 00:00:00 EDT 2012},
month = {Fri Jun 15 00:00:00 EDT 2012}
}