Status Report of the Review of Vacuum Systems and Procedures Tug Arkan, Allan Rowe

Reviews Completed HTS – Implementing Recommendations – New vacuum manifold installed week of 4/4/11 – Procedures still to be updated, approved, and filed VTS – Implementing Recommendations – Hardware updates still required. – Procedures still to be updated, approved, and filed

Reviews Completed cont… SCSPF – Implementing most recommendations (facility limitations prevent all implementation) – Pre-assembly component and cavity preparation improvements started MP9 – Review completed – Hardware improvements in process

MP9 HTS Cavity Prep. Sequence Followed TB9RI024 through complete preparation for HTS. Process Sequence: – Arrived from SCSPF to MP9 under vacuum following HPR and HTS assembly. – Surface cleaned entire exterior of dressed cavity in soft-wall clean room using 4 step wipe-down and blow-off process. Technique was very effective at reducing surface particulates prior to CR entry.

MP9 Cavity Preparation for CR Evaluated ‘lint-free’ wipers on machined helium vessel---did not create substantial particulates. Will retain in cavity prep. process. Final wipe-down/ion-gun blow off after cavity introduced in CR. Total of 4 surface cleanings. – Flange areas always most critical and received most attention.

MP9 Part Preparation Part preparation – Received most rigorous cleaning of any facility— sometimes received 3-4 cleaning cycles before allowed entry into Class 10 CR. All parts individually bagged. – Updated final cleaning procedure to be created and filed. Current procedure not in control system. Process can be implemented throughout other areas to ensure high quality preparation everywhere.

MP9 Part Preparation Part Preparation---other comments – Some process optimization for other areas required due to time commitment of current process at MP9. – Evaluation of parts/hardware at SCSPF, A0, and MP9 to be performed. All techniques slightly different and mostly modified due to manpower availability. Quality of part preparation must be maximized with time available at each facility.

MP9 Backfill Once cavity is in position in CR, it is backfilled with argon in preparation for cold-coupler installation. Fixed backfill rate determined by needle-valve and volumetric flow control panel. Panel pre- set with no adjustment during back-fill. Rate set to DESY orig. spec of 1 standard liter/min. PFFA techniques used on all flange assembly/disassembly

MP9 Backfill During backfill and pump-down, current vacuum system is ‘blind’ to actual pressure above 7 mBar. This rate of rise is most important above 1 mBar as this is when particulates are most likely to migrate in the system. Full range gauge to be installed inside CR on vacuum line and at pumping station so full pressure rise/drop can be monitored from 1050 mBar to UHV.

MP9 Backfill Current process introduces a ‘slug’ of gas from pressurized (1050 mBar) backfill line into cavity when isolation RAV to cavity is opened. The full line (including cavity) pressure equalizes above 8 mBar in about 1 second. Then the panel fills the cavity and backfill line to 1050 mBar in about 25 minutes. A single pump-down/backfill station in the CR will be modified to accommodate a controlled backfill to ‘ease’ in the gas contained in the pre-filled backfill line into the cavity.

MP9 RF Coupler Assembly RF coupler removal from test stand – Delivered as assembly from SLAC – Backfilled using standard argon backfill as used for cavity – 7-minutes to backfill stand – First inspection of coupler RF surfaces since before processing at SLAC. Difficult to make any sort of evaluation w/o potentially contaminating coupler. Quick ‘peek-in’ on surfaces before installing on insertion tool. – Ion-gun blow-out and particulate count before installation on cavity

MP9 RF Coupler Assembly Comments on RF coupler disassembly – Q/C of RF surfaces by quick visual inspection likely not reliable. – We’re trusting that RF processing at SLAC yields a stable surface despite some discoloration or variance in surface sheen or appearance. No standard can be applied to modest differences as all surfaces look somewhat different and can’t be directly compared to one another. – Catastrophic marks or flaking copper are the only likely ‘stops’ we can put on the process at this point. – If RF coupler won’t blow particle free—set aside.

MP9 RF Coupler Assembly Removal of RF coupler blank-off flange yielded SiBr shavings from nuts. Don’t know how to eliminate this. Does not always occur. Installation process carefully controlled with standard PFFA techniques and alignment fixture assistance. Multiple class 10 glove changes during assembly.

MP9 Evacuation Cavity at atmospheric pressure. Pumping line at 4.7 e-6 mBar Used isolation RAV on MP9 vacuum manifold in CR as throttling valve. Could control pressure drop moderately well, but difficult as other groups have seen. Vacuum line pressure rose from 4.7e-6 to 2e-2 mBar in 10 seconds. Line not being pumped at this time. ~28 liters of gas from cavity and vacuum hose increased vacuum system pressure to equilibrium in about 5 minutes.

MP9 Evacuation Don’t know equalization pressure due to gauge reading limit at 7-8 mBar. Calculated equalization pressure is approximately 250 mBar. Cavity + hose = 28 liters at atmosphere. Vacuum line = 83 liters 1e-6 mBar. Opened system to vacuum pumps. Pumped back down to 2.0 e-3 mBar in 20 minutes. New procedure requires equalizing vacuum line and cavity to atmospheric pressure before beginning pump down. Full range gauge will help monitor cavity pressure and drop rate. New by-pass line and throttle valve to be installed.

Particle Counter Test Two types tested with two sampling rates to verify particulate count equivalency. 28 l/min vs. 75 l/min Conclusion-- – Parts clean up on each particle counter at approximately the same time. One counter not necessarily more sensitive than the other. – Zero counts = Zero counts on both counters.

Remaining Work for Review Review A0 practices—cleaning and assembly (today) Submit final written report from reviewers to Champion that details specific recommendations to all areas. Distribute report to all areas. Help integrate all recommendations.