Cryopump Regeneration
Purpose: Cryopump regeneration is necessary whenever the pump temperature monitor exceeds 20 K, with the system set to trip the cryo gate valve if the temperature rises above 25 K. Above this threshold, cryopump efficiency decreases.
Quick Steps
(Note: These instructions mirror those on the comprehensive Cryopump page and should be updated concurrently.)
Preparation and Warming
Setup: Attach a free scroll pump and Pirani gauge at the pumping port of the gate valve (for Bravo systems) or on the roughing manifold (for Echo systems). Activate the pump.
Valve Management: Close the gate valve located in front of the pump.
Displacer Shutdown: Turn off the displacer to stop the cooling process.
Temperature Monitoring: Watch the temperature monitor as the cryopump's temperature rises.
Critical Action: As the temperature reaches 77 K (the boiling point of nitrogen), quickly open the all-metal valve at the pumping port. This step is crucial to prevent over pressurization of the cryopump and the potential bursting of the burst disk.
Regeneration
Continuous Pumping: Allow the scroll pump to run overnight while the temperature continues to rise towards room temperature. Keep pumping until the Pirani gauge indicates a bottomed-out reading.
Sealing the System: Close the all-metal valve and turn off the scroll pump.
Re-pressurization: Recharge the helium side as specified in the wiki [Recharge] procedures.
Cool Down
Restart Displacer: Turn on the cryopump displacer to begin the cooling process again.
Final Temperature Check: Monitor the ultimate temperature. A successful regeneration results in a temperature below 20 K. If the temperature hovers around or above 20 K, consider conducting maintenance on the displacer head. Refer to the wiki for the last recorded full head maintenance to decide on a full or partial head rebuild.
Documentation: Update the wiki cryopump status page with the date and details of the work performed.
Note: If another regeneration is needed soon after, leave the manifold at 250 psi. This may require a helium refill from the tank due to losses when detaching the lines.