19 October 1994 Monitoring deposition of molecular contamination on optics using a temperature-controlled quartz crystal microbalance (TQCM)
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Abstract
Temperature-Controlled Quartz Crystal Microbalance (TQCM) instruments were used in a clean room (under non-vacuum conditions) as an indicator of molecular contamination deposited in optics. The Wide Field Planetary Camera II and the Corrective Optics Space Telescope Axial Replacement, which were installed in the Hubble Space Telescope during the first servicing mission in December 1993, had stringent contamination budgets. While they were in a Goddard Space Flight Center cleanroom undergoing integrated testing, two TQCMs were used to provide an early warning of excessive molecular contamination on a near real- time basis and to provide a measurement of the total contamination deposited over the 50 to 75 day test period. The TQCM frequency, which changes in direct proportion to the mass of material deposited on the exposed crystal, was recorded on a computer located outside the cleanroom and was monitored on an hourly basis with alert limits set for hourly and daily frequency increase. Frequency increase was correlated to peak personnel activity in the area. The results for the period of integrated testing were within budget. The operation of the TQCM is described and the results and analysis are presented.
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William J. Mitchell, William J. Mitchell, } "Monitoring deposition of molecular contamination on optics using a temperature-controlled quartz crystal microbalance (TQCM)", Proc. SPIE 2261, Optical System Contamination: Effects, Measurements, and Control IV, (19 October 1994); doi: 10.1117/12.190156; https://doi.org/10.1117/12.190156
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