American Nuclear Society
Home

Home / Publications / Journals / Fusion Science and Technology / Volume 55 / Number 3

Measurement of Total Condensation on a Shrouded Cryogenic Surface Using a Single Quartz Crystal Microbalance

B. J. Haid, T. N. Malsbury, C. R. Gibson, C. T. Warren

Fusion Science and Technology / Volume 55 / Number 3 / April 2009 / Pages 276-282

Technical Paper / Eighteenth Target Fabrication Specialists' Meeting

A single quartz crystal microbalance (QCM) is cooled to 18 K to measure condensation rates inside of a retractable shroud enclosure. The shroud is designed to minimize condensate on fusion targets to be fielded at the National Ignition Facility (NIF). The shroud has a double-walled construction with an inner wall that may be cooled to 75 to 100 K.

The QCM and the shroud system were mounted in a vacuum chamber and cooled using a cryocooler. Condensation rates were measured at various vacuum levels and compositions and with the shroud open or closed. A technique for measuring total condensate during the cooldown of the system with an accuracy of >1 × 10-6 g/cm2 was also demonstrated. The technique involves a separate measurement of the condensate-free crystal frequency as a function of temperature that is compared to the measurement for the cooldown trend of interest. The shroud significantly reduces the condensation rates of all gases and effectively eliminates H2O condensation.

 
Questions or comments about the site? Contact the ANS Webmaster.
advertisement