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Title: Power balance on a multibeam laser

Journal Article · · Proc. SPIE
DOI:https://doi.org/10.1117/12.2288510· OSTI ID:1427299
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Univ. of Rochester, NY (United States). Lab. for Laser Energetics
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Inertial confinement fusion (ICF) cryogenic experiments on the 60-beam OMEGA laser have strict requirements for the laser energy delivered on target to be power balanced in order to maximize target-irradiation uniformity. For OMEGA, this quantity (power balance) is inferred from measurements of the time-integrated energy and time-resolved, spatially integrated temporal profile of each of the 60 beams at the output of the laser. The work presented here proposes a general definition of power balance as measured at the laser output and discusses the conditions that are fundamental to achieving laser power balance. Power balance necessitates equal gain across all stages of amplification, equal net losses across each amplifier stage, equal frequency conversion (from 1053 nm to 351 nm) of all 60 beams, and equal beam path lengths (beam timing). Typical OMEGA ICF laser pulse shapes consist of one or more short (100-ps) “pickets” followed by a shaped “drive” pulse of 1 to 2 ns. For these experiments, power balance is assessed for the pickets and the drive independently, with the ultimate goal of achieving root-mean-square (rms) imbalance across all 60 beams of less than 2% rms on both. Our work presents a comprehensive summary of laser shot campaigns conducted to significantly improve laser power balance from typical rms values of 4.7% and 5.2%, respectively, to the 3% level for both features along with a discussion of future work required to further reduce the rms power imbalance of the laser system.

Research Organization:
Univ. of Rochester, NY (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA); New York State Energy Research and Development Authority (NYSERDA)
Grant/Contract Number:
NA0001944
OSTI ID:
1427299
Report Number(s):
2017-150, 1385; 0277-786X; 2017-150, 1385, 2342
Journal Information:
Proc. SPIE, Vol. 10511; Conference: LASE, San Francisco, CA (United States), 27 Jan-1 Feb 2018
Country of Publication:
United States
Language:
English

References (5)

National direct-drive program on OMEGA and the National Ignition Facility journal October 2016
High efficiency frequency tripling schemes for high-power Nd: Glass lasers journal September 1981
Random Phasing of High-Power Lasers for Uniform Target Acceleration and Plasma-Instability Suppression journal September 1984
Reduction of laser imprinting using polarization smoothing on a solid-state fusion laser journal April 1999
Predicting and measuring optical pulse shapes on the OMEGA laser system
  • Donaldson, W. R.; Kelly, J. H.; Keck, R. L.
  • CLEO 2001. Technical Digest. Summaries of papers presented at the Conference on Lasers and Electro-Optics. Postconference Technical Digest, Technical Digest. Summaries of papers presented at the Conference on Lasers and Electro-Optics. Postconference Technical Digest (IEEE Cat. No.01CH37170) https://doi.org/10.1109/CLEO.2001.947647
conference January 2001

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Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
Power balance
multibeam laser
OMEGA
direct drive
fusion
high-energy density