13 September 2012 Unintended consequences on vacuum hold time with conversion to PolyCold closed-cycle coolers
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Abstract
In 2009, the Canada-France-Hawaii Telescope converted the dewar for the ESPaDOnS spectrograph from using liquid nitrogen cooling to using a Polycold® closed-cycle cooler. It was found that the higher temperature of the closed-cycle cooler degraded the efficiency of the carbon getter for maintaining the vacuum to the point that vacuum could not be maintained long-term without the pumping of a cold-cathode gauge. This paper will detail this vacuum issue along with some experiments done to show the pumping rates of the carbon getter and cold-cathode vacuum gauges, and describe a light-baffle design for suppressing light from the gauge.
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Tom Benedict, Tom Benedict, Gregory A. Barrick, Gregory A. Barrick, "Unintended consequences on vacuum hold time with conversion to PolyCold closed-cycle coolers", Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 84504M (13 September 2012); doi: 10.1117/12.926428; https://doi.org/10.1117/12.926428
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