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Identification and Removal of High Frequency Temporal Noise in a Nd [electronic resource] : YAG Macro-Pulse Laser Assisted with a Diagnostic Streak Camera

Published:
Washington, D.C. : United States. Dept. of Energy, 2004.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Additional Creators:
Bechtel Nevada (Firm), United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary:
This paper discusses the use of a reference streak camera (SC) to diagnose laser performance and guide modifications to remove high frequency noise from Bechtel Nevada's long-pulse laser. The upgraded laser exhibits less than 0.1% high frequency noise in cumulative spectra, exceeding National Ignition Facility (NIF) calibration specifications. Inertial Confinement Fusion (ICF) experiments require full characterization of streak cameras over a wide range of sweep speeds (10 ns to 480 ns). This paradigm of metrology poses stringent spectral requirements on the laser source for streak camera calibration. Recently, Bechtel Nevada worked with a laser vendor to develop a high performance, multi-wavelength Nd:YAG laser to meet NIF calibration requirements. For a typical NIF streak camera with a 4096 x 4096 pixel CCD, the flat field calibration at 30 ns requires a smooth laser spectrum over 33 MHz to 68 GHz. Streak cameras are the appropriate instrumentation for measuring laser amplitude noise at these very high frequencies since the upper end spectral content is beyond the frequency response of typical optoelectronic detectors for a single shot pulse. The SC was used to measure a similar laser at its second harmonic wavelength (532 nm), to establish baseline spectra for testing signal analysis algorithms. The SC was then used to measure the new custom calibration laser. In both spatial-temporal measurements and cumulative spectra, 6-8 GHz oscillations were identified. The oscillations were found to be caused by inter-surface reflections between amplifiers. Additional variations in the SC spectral data were found to result from temperature instabilities in the seeding laser. Based on these findings, laser upgrades were made to remove the high frequency noise from the laser output.
Report Numbers:
E 1.99:doe/nv/11718--986
doe/nv/11718--986
Subject(s):
Other Subject(s):
Note:
Published through SciTech Connect.
09/23/2004.
"doe/nv/11718--986"
SPIE 26th International Congress in Alexandria, Virginia, September 23, 2004.
Kent Marlett, Bechtel Nevada; Ke-Xun Sun Bechtel Nevada.
Funding Information:
96NV11718
View MARC record | catkey: 14740024