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Message ID: 2504     Entry time: Fri Aug 14 11:17:04 2020
Author: Raymond 
Type: Update 
Category: Cryo vacuum chamber 
Subject: Cooler now operational 

Cryopump is up and running. Initial attempts to run the cooler were stymied by an open circuit in the cold head to compressor connection caused by one of the two accessory port fuses (right, circled in attachment 1). The compressor would run but the valve motor wouldn't start in the cooler itself. I extended the spring in the fuse housing (attachment 2) and it seems to have fixed the problem, as now the valve motor starts at the same time the compressor is turned on. Attachment 1 also shows the highly technical cord management procedure done to reduce the trip hazard caused by the compressor power plug. 

User manual recommendations*:

  • Equalization pressure (when not operating): 270-275psi
    • Currently sits at 270psi
  • Operating pressure: 290-330psi
    • Operating at 300psi
  • Insulating vacuum pressure: 1 x 10-3 Torr
    • Vacuum pressure stabilized at 8.5 x 10-1 Torr
      • Edwards diaphragm pump listed ultimate pressure is 1.5 mbar ≈ 1.1 Torr, so either the multirange gauge is malfunctioning or we're getting better backing pressure than expected from the diaphragm pump. A Pirani gauge will be attached to the vacuum space going forward so we'll see how it compares; either way we're above the recommended insulation pressure. The 11" nipple surrounding the coldhead does become cool to the touch during operation, but it does not get cold enough to create condensation.

*Manuals for both the compressor and the cryocooler are linked on the West Bridge wiki manuals page

Attachment 1: IMG-1190.JPG  1.988 MB  Uploaded Fri Aug 14 12:20:25 2020  | Hide | Hide all
Attachment 2: IMG-1187.JPG  1.795 MB  Uploaded Fri Aug 14 12:20:42 2020  | Hide | Hide all
Attachment 3: IMG-1189.JPG  2.012 MB  Uploaded Fri Aug 14 12:44:50 2020  | Hide | Hide all
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