All the heterodyne receivers at the CSO require periodic cryogen service.
The sidecab receivers and the 850 GHz receiver are housed in hybrid cryostats, with mechanical Gifford McMahon coolers and a liquid helium (LHe) reservoir. The CSO staff will service these receivers.
The wideband 345 GHz receiver (Barney) at the Cassegrain focus is housed in a simple (purple) cryostat cooled by liquid nitrogen (LN2) and LHe. It requires daily cryogen service. When staff are not available, observers may be called upon to Cryogens should only be handled by trained personnel. CSO staff will train novice observers.
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