Evaluation of bakeout effectiveness by optical measurement of a contaminated surface

Hiroshi Yokozawa; Susumu Baba; Eiji Miyazaki; Yugo Kimoto

doi:10.1117/12.929453

15 October 2012 Evaluation of bakeout effectiveness by optical measurement of a contaminated surface

Hiroshi Yokozawa, Susumu Baba, Eiji Miyazaki, Yugo Kimoto

Proceedings Volume 8492, Optical System Contamination: Effects, Measurements, and Control 2012; 84920A (2012) https://doi.org/10.1117/12.929453
Event: SPIE Optical Engineering + Applications, 2012, San Diego, California, United States

Abstract

We attempted to evaluate the effectiveness of bakeout for certain materials by using the “In-Situ Contamination Spectroscopic Analysis Chamber” newly developed by JAXA, in order to measure the optical properties of a surface contaminated by condensed outgas. In the present case, the sample (RTV-S 691; subject to four bakeout conditions) is heated at 125°C and a gold-coated mirror set opposite the sample is cooled at -10°C to collect outgassing from the sample. FT-IR is set to measure the optical properties on the surface of the gold-coated mirror inside the chamber in-situ. A thermoelectric quartz crystal microbalance (TQCM) is installed in the chamber where the view factor to the sample is equivalent to that of the gold-coated mirror used to measure the thickness of deposited contaminants at the same temperature as that of the mirror. The four bakeout conditions are no bakeout, bakeout at 60°C, at 80°C, and at 125°C for 72 hours, respectively. As a result, TQCM data showed an expected curve, revealing a lower deposition rate at higher bakeout temperature. We then plotted the absorbance for obvious FT-IR spectra peaks against the optical path length, as calculated from the deposition thickness measured using the TQCM. The absorption coefficient at certain wavenumbers was found to vary under the four bakeout conditions. This suggests an insufficient deposition thickness on the optical surface. It therefore follows that direct optical measurement should be performed to evaluate bakeout effectiveness as pertaining to the essential purpose of bakeout.

Citation Download Citation

Hiroshi Yokozawa, Susumu Baba, Eiji Miyazaki, and Yugo Kimoto "Evaluation of bakeout effectiveness by optical measurement of a contaminated surface", Proc. SPIE 8492, Optical System Contamination: Effects, Measurements, and Control 2012, 84920A (15 October 2012); https://doi.org/10.1117/12.929453

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