Modeling Temperature and Pressure Gradients During Cooling of Thin-Walled Cryogenic Targets
OAK-B135 Cooling thin-walled capsules filled with deuterium is a critical phase of operation for providing cryogenic direct-drive targets. During cooling to 20 K, buckling and burst forces develop due to transient thermal gradients, thermal expansion differences in the materials of the capsule and permeation cell, and changing permeability of the plastic. This article presents the results of both a steady-state and a transient analysis of the pressure differences across the wall of a thin-walled capsule during the cooling process. The steady-state contribution to the pressure difference arises from two sources: (1) the different thermal contractions of the materials that comprise the permeation cell and capsule and (2) the room-temperature volume of gas in the line connecting the permeation cell to the isolation valve. The transient analysis considers the pressure differences across the capsule wall that arise from the changing temperature gradients within the gas during the cooling cycle. Both effects have been taken into account to determine the approach required to produce fuel-filled thin-walled cryogenic targets more rapidly. Currently, capsules are slowly cooled at a rate of 0.1 K/min to prevent their destruction. This process requires over 45 h to complete. The results of the present model present a faster cooling program that takes into consideration the induced pressure differences, permeation occurring at higher temperatures, and the strength of the capsule. The time to cool a filled target can be reduced by 25% while maintaining capsule survival.
- Research Organization:
- Laboratory for Laser Energetics (US)
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- FC03-92SF19460
- OSTI ID:
- 822400
- Report Number(s):
- DOE/SF-19460-522; 1433; 2003-34; TRN: US0401375
- Journal Information:
- Fusion Science and Technology, Vol. 45; Other Information: Submitted to Fusion Science and Technology; Volume 45; PBD: 15 Mar 2004
- Country of Publication:
- United States
- Language:
- English
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