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Title: The Wavefront Control System for the National Ignition Facility

Abstract

The National Ignition Facility (NIF) requires that pulses from each of the 192 laser beams be positioned on target with an accuracy of 50 {micro}m rms. Beam quality must be sufficient to focus a total of 1.8 MJ of 0.351-{micro}m light into a 600-{micro}m-diameter volume. An optimally flat beam wavefront can achieve this pointing and focusing accuracy. The control system corrects wavefront aberrations by performing closed-loop compensation during laser alignment to correct for gas density variations. Static compensation of flashlamp-induced thermal distortion is established just prior to the laser shot. The control system compensates each laser beam at 10 Hz by measuring the wavefront with a 77-lenslet Hartmann sensor and applying corrections with a 39-actuator deformable mirror. The distributed architecture utilizes SPARC AXi computers running Solaris to perform real-time image processing of sensor data and PowerPC-based computers running VxWorks to compute mirror commands. A single pair of SPARC and PowerPC processors accomplishes wavefront control for a group of eight beams. The software design uses proven adaptive optic control algorithms that are implemented in a multi-tasking environment to economically control the beam wavefronts in parallel. Prototype tests have achieved a closed-loop residual error of 0.03 waves rms. aberrations, the spot sizemore » requirement and goal could not be met without a wavefront control system.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
15005538
Report Number(s):
UCRL-JC-135189
TRN: US0305534
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: 8th International Conference on Accelerator and Large Experimental Physics Control Systems, San Jose, CA (US), 11/27/2001--11/30/2001; Other Information: PBD: 15 Oct 2001
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; ACCELERATORS; ALGORITHMS; ALIGNMENT; COMPUTERS; CONTROL SYSTEMS; DESIGN; FOCUSING; IMAGE PROCESSING; LASERS; MIRRORS; OPTICS; PHYSICS; TARGETS; US NATIONAL IGNITION FACILITY

Citation Formats

Van Atta, L, Perez, M, Zacharias, R, and Rivera, W. The Wavefront Control System for the National Ignition Facility. United States: N. p., 2001. Web.
Van Atta, L, Perez, M, Zacharias, R, & Rivera, W. The Wavefront Control System for the National Ignition Facility. United States.
Van Atta, L, Perez, M, Zacharias, R, and Rivera, W. Mon . "The Wavefront Control System for the National Ignition Facility". United States. https://www.osti.gov/servlets/purl/15005538.
@article{osti_15005538,
title = {The Wavefront Control System for the National Ignition Facility},
author = {Van Atta, L and Perez, M and Zacharias, R and Rivera, W},
abstractNote = {The National Ignition Facility (NIF) requires that pulses from each of the 192 laser beams be positioned on target with an accuracy of 50 {micro}m rms. Beam quality must be sufficient to focus a total of 1.8 MJ of 0.351-{micro}m light into a 600-{micro}m-diameter volume. An optimally flat beam wavefront can achieve this pointing and focusing accuracy. The control system corrects wavefront aberrations by performing closed-loop compensation during laser alignment to correct for gas density variations. Static compensation of flashlamp-induced thermal distortion is established just prior to the laser shot. The control system compensates each laser beam at 10 Hz by measuring the wavefront with a 77-lenslet Hartmann sensor and applying corrections with a 39-actuator deformable mirror. The distributed architecture utilizes SPARC AXi computers running Solaris to perform real-time image processing of sensor data and PowerPC-based computers running VxWorks to compute mirror commands. A single pair of SPARC and PowerPC processors accomplishes wavefront control for a group of eight beams. The software design uses proven adaptive optic control algorithms that are implemented in a multi-tasking environment to economically control the beam wavefronts in parallel. Prototype tests have achieved a closed-loop residual error of 0.03 waves rms. aberrations, the spot size requirement and goal could not be met without a wavefront control system.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2001},
month = {10}
}

Conference:
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