2023-10-05 Meeting notes

• FE developed in 4 cavities (was clean)
• Current rad limits is limiting us below the 90 MV needed to run the laser heater
• Currently in warm and fast cool cycle (80 K)
• Saw a lot of degassing warming up the CM01.
• Dan suggesting we could warm up (in the future) CM01 quite quickly by spoiling the insulating vacuum at 80 K
  • Keep rest of the linac at 80 K
  • Would need to discuss with cryoplant
• Testing CM01 tomorrow. Current schedule has gun SSA work at 1. CM01 check out is before that.
  • Pump down scheduled tomorrow in the AM.
  • Likely CM01 checkout around noon.
  • Check out CM01 like during commissioning (stop if cavity reaches 50 mR/hr)
• Will also checkout CM08. Decarads were placed today. Sebastian is updating the schedule.

Added hardware mode as direct item in interlocks

PV name is admin. Still called admin on epics summary display

EPICS fault status was not propagating to summary display (should be fixed)

Habit of turning off RF to cryo communication during shutdown. Has been admin handled and Sonya is working on making it automated. Implemented for CM32 if hardware mode offline or communication interrupted the cryo heartbeat will die.

New short rack checkout. We should not use it, but we may see faults telling us that a "full rack checkout is needed" now.

HL2-4 was checked out and nothing wrong was found. Set to maintenance done.

Some stepper motor and limit switches were checked and found not to have issues

CM18 and 19 had full LLRF tune up procedure. Will need phase checked.

CM07-4 needs connections checked. Still being worked on.

Found some vacuum events, but most things are pretty old. Sharing google doc of investigation: https://docs.google.com/document/d/1ygw2ZVw23_X0-jTNYgHGw9cBe48bwuuqg4zTbsjcsBM/edit?pli=1

3 vacuum spikes in Sept last year caused by ion pumps tripping off on beamline vacuum. These were on hot days and likely heat induced trips. Maintenance period, but 2 K

• CM01 vacuum event in late sept. Also vacuum events in H1 and H2. Nicole: Also a big spike that might not be real? Since it is not reflected on other gauges?
  • Sebastian: H2-8 now at a lower field due to a quench with large vacuum spikes? Could this be it?
  • Sebastian: was this actually the coupler vacuum? Nicole will double check. Update: was the coupler vacuum
  • We did coupler work on this module. Check if this is the right time.
• They raised the vacuum trip level on the gun because they were tripping too much...
• Lauren talked to Xianghong about the RGA in the vacuum. Xianghong confident he knows what's in there: hydrocarbons
  • Sebastian: hydrocarbon levels seen by RGA are going down
  • Lauren: hydrogen and CO2 there too
• Gun vacuum activity happens regularly with turn on and turn off.
• RGA sensor is not close to the CM. Over 1 m away.
• For this specific thing we are only really interesting in the beamline vacuum, not coupler.
• Nicole: What level of vacuum do we have to hit?
  • Dan: for a single incident very high? E-1 E-2 to move particles.
  • Sebastian: bursts of something lower could still be bad
• Nicole: March power outage had a vacuum spike. Nicole wants to look at it more.
• Collimaters? Nothing bad seen. No temp spikes and they are barely used (mostly in the out position).

• Crater in cathode. People assume stays in gun but does it? Nothing on RGA. Nicole looking into

• Dan: was there a change in operating parameters between times? Did we only notice because the LBLM calibration was dialed in?
• On shift where it was noticed the LBLM was not being worked on. Alan was called in BECAUSE the LBLM was causing trips.
• One gun LBLM was not calibrated well until recently.

Looking at modeling gun bursts? Sebastian might talk to Dominique?