Do not touch the displacers and metal pump shaft; fingerprints and moisture will crystallize when cooled down and will damage moving parts. The new cold head comes in a new sleeve pre-pressurized with He. Sleeves were not exchanged during this visit. Stage 2 Copper-lined Stage 1 Cold head sleeve He ports / power socket Displacers Crank case Motor housing Oscillating pump mechanism
Cold head swap procedure: 1. Removed flex line connections at cold head. Some He gas was heard escaping, this is okay. 2. Attached a gauged bleed valve (see diagram) to the He return (outlet) port on the cold head, bled inner pressure to atmosphere. 3. Turned cold head power on and allowed it to cycle several times to push out any remaining pressure within the system. The internal volume must be at atmosphere for safe disassembly. 4. Removed the 4 hex bolts from the top of the crank case which secure the head in its sleeve. 5. Removed the cold head from its mount by lifting vertically with a grip on the crank case / motor housing. The fit is tight so some twisting may be necessary.
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- Summer '14
- Bolted joint, Fasteners, Cryostat Cold Heads