dorsal/arxiv
View SchemaThe Wavefront Control System for the National Ignition Facility
| Authors | Lewis Van Atta, Mark Perez, Richard Zacharias, William Rivera |
|---|---|
| Categories | |
| ArXiv ID | physics/0111104 |
| URL | https://arxiv.org/abs/physics/0111104 |
| Journal | eConf C011127 (2001) WEcT002 |
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 um rms. Beam quality must be sufficient to focus a total of 1.8 MJ of 0.351-um light into a 600-um-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.
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"abstract": "The National Ignition Facility (NIF) requires that pulses from each of the\n192 laser beams be positioned on target with an accuracy of 50 um rms. Beam\nquality must be sufficient to focus a total of 1.8 MJ of 0.351-um light into a\n600-um-diameter volume. An optimally flat beam wavefront can achieve this\npointing and focusing accuracy. The control system corrects wavefront\naberrations by performing closed-loop compensation during laser alignment to\ncorrect for gas density variations. Static compensation of flashlamp-induced\nthermal distortion is established just prior to the laser shot. The control\nsystem compensates each laser beam at 10 Hz by measuring the wavefront with a\n77-lenslet Hartmann sensor and applying corrections with a 39-actuator\ndeformable mirror. The distributed architecture utilizes SPARC AXi computers\nrunning Solaris to perform real-time image processing of sensor data and\nPowerPC-based computers running VxWorks to compute mirror commands. A single\npair of SPARC and PowerPC processors accomplishes wavefront control for a group\nof eight beams. The software design uses proven adaptive optic control\nalgorithms that are implemented in a multi-tasking environment to economically\ncontrol the beam wavefronts in parallel. Prototype tests have achieved a\nclosed-loop residual error of 0.03 waves rms.",
"arxiv_id": "physics/0111104",
"authors": [
"Lewis Van Atta",
"Mark Perez",
"Richard Zacharias",
"William Rivera"
],
"categories": [
"physics.ins-det"
],
"journal_ref": "eConf C011127 (2001) WEcT002",
"title": "The Wavefront Control System for the National Ignition Facility",
"url": "https://arxiv.org/abs/physics/0111104"
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