Thermal recovery of NIF amplifiers

Steven B. Sutton; Christopher D. Marshall; Charles S. Petty; Larry K. Smith; Bruno M. Van Wonterghem; Steven Mills

doi:10.1117/12.294344

8 December 1997 Thermal recovery of NIF amplifiers

Steven B. Sutton, Christopher D. Marshall, Charles S. Petty, Larry K. Smith, Bruno M. Van Wonterghem, Steven Mills

Proceedings Volume 3047, Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference; (1997) https://doi.org/10.1117/12.294344
Event: Second International Conference on Solid State Lasers for Application to ICF, 1996, Paris, France

Abstract

The issue of thermal recovery of the NIF amplifiers has taken on increased emphasis as program goals move toward increasing the shot rate to once every four hours. This paper addresses the technical issues associated with achieving thermal recovery in the NIF amplifiers. We identify two temperature related thermal recovery quantities: (1) the difference between the average slab temperature and the temperature of other surfaces in the amplifier cavity, and (2) the temperature difference in the slab over the aperture. The first quantity relates to optical disturbances in the gas columns in the system, while the second quantity is associated with optical aberrations in the laser media itself. Calculations and experiments are used to quantify recovery criteria, and develop cooling approaches. The cooling approaches discussed are (1) active cooling of the flashlamps with ambient gas and chilled gas, and (2) active cooling of the slab edge cladding. Calculations indicate that the NIF baseline cooling approach of 20 cfm per lamp ambient temperature gas flow in both the central and side flashlamp cassettes is capable of meeting thermal recovery requirements for an 8 hour shot period, while to achieve a 4 hour shot period requires use of chilled gas and edge cladding cooling. In addition, the effect of changing the amplifier cavity and beamtube fill gas from nitrogen to helium is addressed, showing that a factor of 8 reduction in the sensitivity to thermal disturbances is possible.

Citation Download Citation

Steven B. Sutton, Christopher D. Marshall, Charles S. Petty, Larry K. Smith, Bruno M. Van Wonterghem, and Steven Mills "Thermal recovery of NIF amplifiers", Proc. SPIE 3047, Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference, (8 December 1997); https://doi.org/10.1117/12.294344

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