Next Meeting
Agenda for Next Meeting
Item Principal Time ---- ---------- -------- Status of Open Action Items All 5 min Update on Gun Refurbishment Biallas/Siggins 10 min Tasks for Phase-Space Setup Bohn/All 40 min New Issues All 5 min
This Week's Attendees
J. Bennett, C. Bohn, J. Boyce, D. Douglas, F. Dylla, R. Evans, J. Fugitt, A. Grippo, L. Harwood, K. Jordan, G. Krafft, R. Li, L. Merminga, G. Neil, D. Oepts, P. Piot, M. Spata, T. Siggins, R. Walker, B. Yunn
Closed Action Items
Items of Discussion
There was no beam operations this week. Last weekend, expecting to be checking out diagnostics (specifically the Happek devices) in some depth through the week, we heat treated the cathode so we could start fresh. On Monday afternoon, after cesiation, we attempted to ramp the gun voltage to 350 kV without using the conditioning resistor. Unfortunately the gun began arcing at 300 kV. We therefore inserted the conditioning resistor and did high-voltage processing overnight and part of Tuesday, eventually reaching 420 kV. After recesiation, the photoresponse of the cathode was very poor. Consequently we did another heat-treatment cycle and recesiation, but could not get past 318 kV without arcing. There was evidence of field emission from the cathode itself, and so we were concerned that arcing had splattered impurities over the gun's interior as had happened early February. Therefore we decided to polish the surfaces electrically, i.e., do more high-voltage processing. It turned out to be very easy to go back to 420 kV, where the gun sat quiet, and from that we concluded the cathode is bad but the gun's surfaces are not likely to be contaminated with splattered material. Consequently we decided once again (last night) to recesiate in hopes the cathode would recover. It did not, but exhibited field emission at 350 kV. Thus, today we opened the gun to proceed with changing out the wafer. We also developed a detailed timeline for refurbishment, and the entire process will take two weeks. If all goes well, beam operations will resume 1 Jun 98.
This week's developments were certainly unplanned and constitute a setback; however, the downtime will enable us to turn attention to other productive activities that had been languishing. For one, we will be able to complete a great deal of remaining installation, including in particular the second 180-degree dipole magnet. Two weeks from now the machine will look to the eye to be complete. Still missing will be the sextupole magnets, due in late July, some air-core correctors, and the beam scrapers, but nearly all other hardware should be in place. Happek, it turns out, could not visit this week after all because he was unable to complete fully his instrumentation. Thus the downtime enables him to finish carefully his two interferometric bunch-length monitors and to install and carefully check them out without beam. G. Krafft continues to work with Happek to coordinate completion of the diagnostic and arrange his visit. At this writing (1555, 15 May 98), he is planning to arrive here Monday, 18 May 98. The time also gives us a much-needed opportunity to digest what we have learned thus far about the machine, and to write detailed procedures for establishing "lasing-quality" electron beam.
Regarding development of procedures, the downtime has already begun to pay off. Released from the control room, D. Douglas was able to parlay into a top-level procedure the outcome of a meeting C. Bohn held this week to delineate the essential steps for setting up the electron-beam phase space at the wiggler for lasing. He presented his Phase Space Setup Metaprocedure at today's meeting. It is sensible and appropriately thorough, and Douglas also delineated the tasks necessary to support the Metaprocedure (thanks for the nice job, Dave!). The essential goals of the Metaprocedure are:
K. Jordan presented an overview of the analog monitoring system (AMS) and summarized its status. The first 50% of the AMS (which would provide for the bulk of signals related to the straight-ahead machine) is nearing completion and needs a little less than 1 man-month of labor to bring on line. It carries a "Should" priority for first light, and accordingly, it will be completed as time allows. Jordan reported that there are 32 input channels that are still unassigned, and he requests that people e-mail their requirements to him by Tuesday next week so he can finish the hardware and provide input to the Software Group. As presently configured, the AMS provides 14 output channels in the MCC, and they will be assigned based on the requirements Jordan receives. Plans are that, once assigned, each input is "fixed", but it can be reassigned as necessary by way of the FEL Configuration Change Form that we are now using.
Status of the remaining top-level MUST-priority prerequisites to lasing is the same as reported last week.
New Issues
None.
New Action Items
Old Action Items
Test Plans in Work
Procedures in Work
Metaprocedure for Phase Space Setup Douglas, finalize 29 May 98 Emittance Growth from CSR
Procedures Needed for Recirculation