Abstract
Calibration of the Harvard College Observatory spectrometers that are to fly aboard the Apollo telescope mount (ATM) required a completely clean vacuum system having the capability for pumping hydrogen, helium, argon, and other inert gases at high speeds between 10−6 and 10−8 Torr. The spectrometer performance would be degraded if contaminated by exposure to hydrocarbons, electromagnetic radiation, or metallic films. For this reason, a cryogenically pumped system was selected. This paper describes the concept, development, and operation of the vacuum system which was both cryo-condensation and cryosorption pumped in the molecular flow range. Molecular sieve, bonded to liquid helium-cooled panels, provided the clean, fast, and economical pumping device. Data presented show pumping speeds measured, adsorbent capacity of molecular sieve, liquid helium consumption rates, and cryogenic performance of the system. This data permits analysis of the cryo-vacuum pumping technique for other applications.
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