Next Meeting
Agenda for Next Meeting
Item Person Responsible Time ---- ------------------ -------- Status of Open Action Items All 5 min Scheduling and Commissioning Program Bohn/All 50 min New Issues All 5 min
This Week's Attendees
J. Bennett, S. Benson, G. Biallas, C. Bohn, D. Douglas, M. Drury, F. Dylla, J. Fugitt, L. Harwood, A. Hofler, K. Jordan, R. Lauze, R. Li, G. Neil, D. Oepts, M. Shinn
Closed Action Items
Items of Discussion
This week we ran up to 1.2 mA beam at 38 MeV energy to the straight-ahead dump. The machine configuration presently allows us to turn on and "immediately" run current in the range 0.6-0.7 mA. It remains to do some "fine tuning" of the electron beam to do better. We will be working on it. Our immediate commissioning goals continue to be (1) find and fix what doesn't work, (2) achieve stable 1.1 mA, 38 MeV beam of sufficiently good beam quality at the wiggler, and (3) achieve a reproducible machine setup that can be restored (turned on) quickly.
We need stability on a time scale commensurate with the cathode lifetime, and we have been gathering data to determine it. Midweek we did two sustained cw runs that indicated the cathode e-folding time was in the range 13-17 hours, but this was after using it since 27 Mar 98. We recesiated the cathode yesterday and will be gathering more data. What we have seen thus far is favorable. If the period between recesiation were to be 24 hours (3 shifts), that would be favorable both for commissioning and for users.
Regarding diagnostics, this week we commissioned the two M_56 cavities that will provide information about longitudinal phase space, we calibrated and now continuously use the current-monitor cavity in conjunction with the picoammeters at the beam dumps, and we debugged the hardware for the second multislit transverse-emittance monitor. We also set up the energy-recovery dump and put tune-up beam into it in preparation for doing a "zero-phasing" measurement of the bunch length coming out of the cryomodule. We will attempt to get a data point tonight.
In summary, people have continued to work very hard, and the successes over the last two weeks (going from ľA to mA beam in that short time!) reflect their efforts. We are continuing along the lines outlined above.
Next week we begin to have only one FEL'er (with another FEL'er on standby in case of emergency) and one CEBAF operator assigned to each shift. Assignments for the next two weeks are:
C. Bohn led a discussion concerning the status of prerequisites to inserting the wiggler and trying to get first light. As delineated in last week's minutes, the prerequisites, and their status, are:
1. Support of CEBAF operators. Start using them NOW!
Status: Going well; will increase starting Monday. We still need
to start an "Operator Limits" log.
2. Stable 1.1 mA, 38 MeV beam with sufficiently good beam quality.
Status: Current and energy achieved; stability and quick turn-on need
work. As a start, we need to stabilize the Conoptics 305 that gates the
drive laser's electro-optic cells. We need to improve the injector
settings and monitor their stability. G. Biallas presented an outline of
his cursory thoughts for doing so. The topic was discussed in detail today
in a follow-on meeting, and appropriate procedures and test plans for
initial efforts will be available shortly. S. Benson pointed out that for
a confident attempt at first light the normalized rms transverse and
longitudinal emittances at the wiggler need to be better than about 9
mm-mrad (not "<20 mm- mrad") and 35 keV-deg, respectively, with 60 pC
bunches. PARMELA predicts 5 mm-mrad and 10 keV-deg, so there is
significant margin.
3. Good (>10 hr) cathode lifetime.
Status: Preliminary indications are favorable.
4. Working diagnostics.
New Issues
None.
New Action Items
Old Action Items
Procedures in Work
Emittance Growth from CSR