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Title: Optical smoothing of laser imprinting in planar-target experiments on OMEGA EP using multi-FM 1-D smoothing by spectral dispersion

Abstract

Direct-drive ignition on the National Ignition Facility (NIF) requires single-beam smoothing to minimize imprinting of laser nonuniformities that can negatively affect implosion performance. One-dimensional, multi-FM smoothing by spectral dispersion (SSD) has been proposed to provide the required smoothing [J. A. Marozas, J. D. Zuegel, and T. J. B. Collins, Bull. Am. Phys. Soc. 55, 294 (2010)]. A prototype multi-FM SSD system has been integrated into the NIF-like beamline of the OMEGA EP Laser System. Experiments have been performed to verify the smoothing performance by measuring Rayleigh–Taylor growth rates in planar targets of laser-imprinted and preimposed surface modulations. Multi-FM 1-D SSD has been observed to reduce imprint levels by ~50% compared to the nominal OMEGA EP SSD system. In conclusion, the experimental results are in agreement with 2-D DRACO simulations using realistic, time-dependent far-field spot-intensity calculations that emulate the effect of SSD.

Authors:
ORCiD logo [1];  [1];  [1];  [2];  [1]; ORCiD logo [1];  [1];  [1];  [1];  [1];  [1];  [3];  [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Univ. of Rochester, Rochester, NY (United States)
  2. Univ. of Michigan, Ann Arbor, MI (United States)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Univ. of Rochester, NY (United States). Lab. for Laser Energetics
Sponsoring Org.:
USDOE
OSTI Identifier:
1328777
Grant/Contract Number:
NA0001944
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 9; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; diffraction gratings; optical dispersion; x-ray optics; optical depth; speckle patterns

Citation Formats

Hohenberger, M., Shvydky, A., Marozas, J. A., Fiksel, G., Bonino, M. J., Canning, D., Collins, T. J. B., Dorrer, C., Kessler, T. J., Kruschwitz, B. E., McKenty, P. W., Meyerhofer, D. D., Regan, S. P., Sangster, T. C., and Zuegel, J. D. Optical smoothing of laser imprinting in planar-target experiments on OMEGA EP using multi-FM 1-D smoothing by spectral dispersion. United States: N. p., 2016. Web. doi:10.1063/1.4962185.
Hohenberger, M., Shvydky, A., Marozas, J. A., Fiksel, G., Bonino, M. J., Canning, D., Collins, T. J. B., Dorrer, C., Kessler, T. J., Kruschwitz, B. E., McKenty, P. W., Meyerhofer, D. D., Regan, S. P., Sangster, T. C., & Zuegel, J. D. Optical smoothing of laser imprinting in planar-target experiments on OMEGA EP using multi-FM 1-D smoothing by spectral dispersion. United States. doi:10.1063/1.4962185.
Hohenberger, M., Shvydky, A., Marozas, J. A., Fiksel, G., Bonino, M. J., Canning, D., Collins, T. J. B., Dorrer, C., Kessler, T. J., Kruschwitz, B. E., McKenty, P. W., Meyerhofer, D. D., Regan, S. P., Sangster, T. C., and Zuegel, J. D. 2016. "Optical smoothing of laser imprinting in planar-target experiments on OMEGA EP using multi-FM 1-D smoothing by spectral dispersion". United States. doi:10.1063/1.4962185. https://www.osti.gov/servlets/purl/1328777.
@article{osti_1328777,
title = {Optical smoothing of laser imprinting in planar-target experiments on OMEGA EP using multi-FM 1-D smoothing by spectral dispersion},
author = {Hohenberger, M. and Shvydky, A. and Marozas, J. A. and Fiksel, G. and Bonino, M. J. and Canning, D. and Collins, T. J. B. and Dorrer, C. and Kessler, T. J. and Kruschwitz, B. E. and McKenty, P. W. and Meyerhofer, D. D. and Regan, S. P. and Sangster, T. C. and Zuegel, J. D.},
abstractNote = {Direct-drive ignition on the National Ignition Facility (NIF) requires single-beam smoothing to minimize imprinting of laser nonuniformities that can negatively affect implosion performance. One-dimensional, multi-FM smoothing by spectral dispersion (SSD) has been proposed to provide the required smoothing [J. A. Marozas, J. D. Zuegel, and T. J. B. Collins, Bull. Am. Phys. Soc. 55, 294 (2010)]. A prototype multi-FM SSD system has been integrated into the NIF-like beamline of the OMEGA EP Laser System. Experiments have been performed to verify the smoothing performance by measuring Rayleigh–Taylor growth rates in planar targets of laser-imprinted and preimposed surface modulations. Multi-FM 1-D SSD has been observed to reduce imprint levels by ~50% compared to the nominal OMEGA EP SSD system. In conclusion, the experimental results are in agreement with 2-D DRACO simulations using realistic, time-dependent far-field spot-intensity calculations that emulate the effect of SSD.},
doi = {10.1063/1.4962185},
journal = {Physics of Plasmas},
number = 9,
volume = 23,
place = {United States},
year = 2016,
month = 9
}

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  • Direct-drive ignition on the National Ignition Facility (NIF) requires single-beam smoothing to minimize imprinting of laser nonuniformities that can negatively affect implosion performance. One-dimensional, multi-FM smoothing by spectral dispersion (SSD) has been proposed to provide the required smoothing [Marozas et al., Bull. Am. Phys. Soc. 55, 294 (2010)]. A prototype multi-FM SSD system has been integrated into the NIF-like beamline of the OMEGA EP Laser System. Experiments have been performed to verify the smoothing performance by measuring Rayleigh–Taylor growth rates in planar targets of laser-imprinted and preimposed surface modulations. Multi-FM 1-D SSD has been observed to reduce imprint levels bymore » ∼50% compared to the nominal OMEGA EP SSD system. The experimental results are in agreement with 2-D DRACO simulations using realistic, time-dependent far-field spot-intensity calculations that emulate the effect of SSD.« less
  • We demonstrate a laser beam-smoothing technique known as polarization smoothing. A birefringent optical wedge splits the individual laser beams into two orthogonally polarized beams that, when coupled with a distributed phase plate, produce two speckle patterns shifted with respect to one another. This instantaneously reduces the on-target nonuniformity by a factor of {radical}(2). We measured this reduction optically and its effect is demonstrated in laser-driven targets. {copyright} {ital 1999 American Institute of Physics.}
  • A one-dimensional (1-D) smoothing by spectral dispersion (SSD) system for smoothing focal-spot nonuniformities using multiple modulation frequencies has been commissioned on one long-pulse beamline of OMEGA EP, the first use of such a system in a high-energy laser. Frequency modulation (FM) to amplitude modulation (AM) conversion in the infrared (IR) output, frequency conversion, and final optics affected the accumulation of B-integral in that beamline. Modeling of this FM-to-AM conversion using the code Miró. was used as input to set the beamline performance limits for picket (short) pulses with multi-FM SSD applied. This article first describes that modeling. The 1-D SSDmore » analytical model of Chuang is first extended to the case of multiple modulators and then used to benchmark Miró simulations. Comparison is also made to an alternative analytic model developed by Hocquet et al. With the confidence engendered by this benchmarking, Miró results for multi-FM SSD applied on OMEGA EP are then presented. The relevant output section(s) of the OMEGA EP Laser System are described. The additional B-integral in OMEGA EP IR components upstream of the frequency converters due to AM is modeled. The importance of locating the image of the SSD dispersion grating at the frequency converters is demonstrated. In conclusion, since frequency conversion is not performed in OMEGA EP’s target chamber, the additional AM due to propagation to the target chamber’s vacuum window is modeled.« less
  • Laser beam smoothing achieved with 1-THz-bandwidth, two-dimensional smoothing by spectral dispersion and polarization smoothing on the 60-beam, 30-kJ, 351-nm OMEGA laser system is reported.