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Title: A four-color beam smoothing irradiation system for laser-plasma interaction experiments at LLNL

Abstract

A novel four-color beam smoothing scheme with a capability similar to that planned for the proposed National Ignition Facility has been deployed on the Nova laser, and has been successfully used for laser fusion experiments. Wavefront aberrations in high power laser systems produce nonuniformities in the energy distribution of the focal spot that can significantly degrade the coupling of the energy into a fusion target, driving various plasma instabilities. The introduction of temporal and spatial incoherence over the face of the beam using techniques such as smoothing by spectral dispersion (SSD) can reduce these variation in the focal irradiance when averaged over a finite time interval. We developed a multiple frequency source that is spatially separated into four quadrants, each containing a different central frequency. Each quadrant is independently converted to the third harmonic in a four-segment Type I/ Type II KDP crystal array with independent phase-matching for efficient frequency conversion. Up to 2.3 kJ of third harmonic light is generated in a 1 ns pulse, corresponding to up to 65% conversion efficiency. SSD is implemented by adding limited frequency modulated bandwidth to each frequency component. Smoothing by spectral dispersion is implemented during the spatial separation of the FM modulatedmore » beams to provide additional smoothing, reaching a 16% rms intensity variation level. The four- color system was successfully used to probe NIF-like plasmas, producing {lt} 1% SBS backscatter at {gt} 2x10{sup 15} W/cm{sup 2}. This paper discusses the detailed implementation and performance of the segmented four-color system on the Nova laser system.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
372672
Report Number(s):
UCRL-JC-121270; CONF-9505264-37
ON: DE96050344; TRN: 96:024958
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: 1. annual solid-state lasers for application to inertial confinement fusion meeting, Monterey, CA (United States), 30 May - 2 Jun 1995; Other Information: PBD: 26 Jun 1995
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; 42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES; SOLID STATE LASERS; FREQUENCY MIXING; LASER FUSION REACTORS; NOVA FACILITY; BEAM DYNAMICS; FREQUENCY CONVERTERS; TESTING; INERTIAL CONFINEMENT

Citation Formats

Pennington, D.M., Henesian, M.A., Wilcox, R.B., Weiland, T.L., Eimerl, D., Ehrlich, R.B., Laumann, C.W., and Miller, J.L. A four-color beam smoothing irradiation system for laser-plasma interaction experiments at LLNL. United States: N. p., 1995. Web.
Pennington, D.M., Henesian, M.A., Wilcox, R.B., Weiland, T.L., Eimerl, D., Ehrlich, R.B., Laumann, C.W., & Miller, J.L. A four-color beam smoothing irradiation system for laser-plasma interaction experiments at LLNL. United States.
Pennington, D.M., Henesian, M.A., Wilcox, R.B., Weiland, T.L., Eimerl, D., Ehrlich, R.B., Laumann, C.W., and Miller, J.L. Mon . "A four-color beam smoothing irradiation system for laser-plasma interaction experiments at LLNL". United States. https://www.osti.gov/servlets/purl/372672.
@article{osti_372672,
title = {A four-color beam smoothing irradiation system for laser-plasma interaction experiments at LLNL},
author = {Pennington, D.M. and Henesian, M.A. and Wilcox, R.B. and Weiland, T.L. and Eimerl, D. and Ehrlich, R.B. and Laumann, C.W. and Miller, J.L.},
abstractNote = {A novel four-color beam smoothing scheme with a capability similar to that planned for the proposed National Ignition Facility has been deployed on the Nova laser, and has been successfully used for laser fusion experiments. Wavefront aberrations in high power laser systems produce nonuniformities in the energy distribution of the focal spot that can significantly degrade the coupling of the energy into a fusion target, driving various plasma instabilities. The introduction of temporal and spatial incoherence over the face of the beam using techniques such as smoothing by spectral dispersion (SSD) can reduce these variation in the focal irradiance when averaged over a finite time interval. We developed a multiple frequency source that is spatially separated into four quadrants, each containing a different central frequency. Each quadrant is independently converted to the third harmonic in a four-segment Type I/ Type II KDP crystal array with independent phase-matching for efficient frequency conversion. Up to 2.3 kJ of third harmonic light is generated in a 1 ns pulse, corresponding to up to 65% conversion efficiency. SSD is implemented by adding limited frequency modulated bandwidth to each frequency component. Smoothing by spectral dispersion is implemented during the spatial separation of the FM modulated beams to provide additional smoothing, reaching a 16% rms intensity variation level. The four- color system was successfully used to probe NIF-like plasmas, producing {lt} 1% SBS backscatter at {gt} 2x10{sup 15} W/cm{sup 2}. This paper discusses the detailed implementation and performance of the segmented four-color system on the Nova laser system.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1995},
month = {6}
}

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