Next Meeting

Date: 21 Nov 97

Time: 0830-0930

Place: FEL Facility Break Room

Agenda for Next Meeting

                Item                             Person Responsible     Time
                ----                             ------------------  --------
Status of Action Items                                  All             5 min
Scheduling Update                                       Bohn           15 min
Progress Report on Commissioning                        Legg/Bohn       5 min
Cryounit Noise, Residual and Microphonic                Merminga       10 min
FEL Commissioning Metaprocedure                         Neil           15 min
New Issues                                              All             5 min
Agenda for next week                                    All             5 min

This Week's Attendees

J. Bennett, G. Biallas, J. Bisognano, C. Bohn, J. Boyce, D. Douglas, F. Dylla, D. Engwall, J. Fugitt, E. Gilmann (NSU), A. Hofler, C. Hovater, K. Jordan, G. Krafft, R. Legg, R. Li, L. Merminga, J. Musson, G. Neil, P. Piot, J. Preble, Q.-S. Shu, R. Walker, B. Yunn

Closed Action Items

The following actions from last week's report were closed out:

• FEL Commissioning Team: Inform C. Bohn and R. Legg by e-mail if you are planning vacation during Thanksgiving week. Status: Query extended to include all near-term vacation plans. Here's the tally:

        Bohn                            11/25-28/97, 12/22/97 - 1/1/98
        Engwall                         12/23-30/97
        Jordan                          11/23-30/97
        Krafft                          11/23-30/97
        Legg                            12/8/97
        Neil                            11/25/97 - 1/6/98
        Shu                             11/25/97 - 12/2/97
        Walker                          11/15/97 - 12/2/97
        Yunn                            12/15/97 - 1/21/98

• Douglas: Develop with J. Karn, et. al. an installation strategy for the DV dipoles consistent with FEL commissioning milestones. Status: See Items of Discussion below.
• Douglas: Lead the "FEL Magnet Team" toward developing a viable plan for resolving the DQ good-field problem. Status: See Items of Discussion below.
• Legg: Resolve issue of inductive heating of straight-ahead dump line. Status: Based on CEBAF experience, this appears not to be a problem provided the pipe thickness is less than 1 mm. Legg's spread-sheet calculations support this inference. Wiseman wants to include a ceramic tube. He has Legg's spread sheet to aid the design.
• Bohn: Work with M7 to identify system owners and their responsibilities, maintenance provisions, and escalation policy. Status: Bohn presented the list of Maintenance Group Leaders for the FEL to the attendees. It is being used as a basis for developing a call list. Escalation policy is automatic contact of System Owner if problem is unresolved after 2 hours of maintenance first-aid.
• Bohn: Work with M7 to establish criteria for transferring the FEL as a user facility to the Operations Department. Status: "Tabled" (meaning "deferred to deity").

Items of Discussion

        Shift times presently differ for weekdays and weekends.  They are:
        Weekdays:  Owl @ 2300-0600, Day @ 0600-1530, Swing @ 1530-2300.
        Weekends:  Owl @ 0000-0800, Day @ 0800-1600, Swing @ 1600-0000.

Commissioning over Thanksgiving break and weekend will be on a voluntary basis, with no formally established shift assignments. Work on Thanksgiving Day is, by proclamation, verboten!

R. Legg and J. Preble presented this week's commissioning highlights:

• The injector is ready for running beam through the cryounit. The air-core corrector that had been removed for characterization in the Magnet Test Stand was returned and reinstalled. A sticky valve after the cryounit needs repair, which should be accomplished today. Wednesday night the drive laser went down, but M. Shinn will be able to replace the defective part today. Consequently, plans are to run beam through the cryounit this weekend.
• SRF and rf commissioning of the cryounit was completed. Nominal operating cavity gradients are 12 MV/m for the entrance cavity and 8.5 MV/m for the exit cavity, with unloaded Q at 5x10^9.
• SRF commissioning of the cryomodule is nearly complete. Starting at the entrance cavity, the nominal operating gradients of the 8 cavities are (in MV/m): 9.5, 11.5, 14 (not final), TBD tonight, 11, 14, 12, and 11. Plans are to consider srf commissioning to be complete after all gradients are set, but without measuring unloaded Q. Cryo (specifically, CHL) approves, but wishes to know these values sometime, as do we. Bohn and Preble will work together to fold in the unloaded Q measurements at opportune times during machine commissioning. RF commissioning of the cryomodule is slated for Monday through Friday of next week. Preble advised that commissioning of the vacuum-interlock system for the cryounit is still incomplete. He will coordinate with D. Eardley today to spur its completion.

B. Yunn outlined his recent injector modelling, done in conjunction with srf commissioning of the cryounit. At gradients of 12 MV/m and 8 MV/m and rf phases of 0 deg and -42.5 deg for the entrance and exit cavities, respectively, he finds an output kinetic energy of 8.5 MeV. The situation improves considerably with the exit cavity powered at 8.5 MV/m, for which its rf phase is -35 deg, producing an output kinetic energy of 9.1 MeV, a value compatible with the beam transport system. Yunn still needs to finalize the machine settings and will do so by Monday, 17 Nov 97.

D. Douglas discussed the status of the DV (injection-extraction) dipoles. Regarding DVs, the problem is unwanted fringe fields extending over the beamline from the injector and the beamline leading to the energy-recovery dump. Two fixes are in consideration. The first is to build a new Y-chamber for the energy-recovery dump and leave the magnets out altogether for first light; the present Y-chamber has insufficient acceptance without the magnet. Second is to lengthen the field clamp to extend over the whole Y, then add a coil to counter the fringe field. The second option is clearly preferred from a programmatic viewpoint, since there is insufficient cost and schedule to build another Y-chamber and no one wants to postpone resolution. TOSCA runs continue to be in progress and hopefully will be completed imminently. A working code would permit us to set parameters for the modifications. Absent that, we will likely need to establish parameters in situ.

Douglas also discussed the status of the DQ (reverse-bend) dipoles, for which the good- field region is a factor of two too small, achieving dB/B = 10^-4 at ±6 cm rather than at the specified ±10 cm. The transverse beam size in the horizontal plane is very large through these magnets. DIMAD results suggest a do-nothing approach would put the acceptance of the beam- transport system marginally at 5%, and probably less than that. Comparison with CEBAF magnet performance also gives rise to concern. Possible fixes include adding surface coils and/or shims. Efficacy of surface coils is presently being assessed in the Magnet Test Stand.

J. Musson presented a brief overview of the design of the FEL master-oscillator (MO) system and measured results after its installation. The MO involves four legs, one for the injector and the other three for three cryomodules (meaning only two are presently in use). It is based on a STAR configuration, with cables anchored to the LCW input lines and insulation wrapped around the cables and LCW lines. The LCW temperature is measured to be stable to ±1 deg F. Measured performance for all four legs is about 0.1 deg phase variation for 1 deg F temperature variation. This is in a quiescent environment, i.e., without the accelerator in full-up operation, but the results are nevertheless quite promising.

New Issues

New Action Items

• Bohn/Walker: Develop maintenance call list for FEL. (due 17 Nov 97)
• Preble: Coordinate with D. Eardley to complete commissioning of the vacuum-interlock system. (due 14 Nov 97)

Old Action Items

• Piot: Do preliminary tests of tomography software obtained from www. (due 14 Nov 97) Status: Actively being pursued, with a few technical difficulties to resolve. Should be complete within 2-3 workdays.
• Yunn: Model cryounit with cavity performance set at 12 MV/m and 8 MV/m for the entrance and exit cavities, respectively. Feed information to J. Preble, and iterate as required. Status: Yunn's results are reported above. He is establishing the settings for the 12-8.5 gradients. (due 17 Nov 97)
• Wiseman: Determine vacuum-pump requirements for the first-light dump line. (due 12 Nov 97) Status: L. Dillon-Townes did the calculations and is scheduling a meeting on 17 Nov 97 to discuss them.
• Biallas: Check on availability of spare CEBAF air-core correctors. Status: There are 18 corrector pairs needed for first light. Biallas has been able to find 7 spare pairs. Air-core correctors for the straight-ahead beam line are scheduled to be received from the vendor just after Thanksgiving. The first article is to be shipped today. However, there is some concern about slip in delivery schedule, so Biallas will check with the Shop for more spares. (due 17 Nov 97)

Procedures in Work

First Light Setup

Thread to Straight-Ahead Dump               Douglas, finalize by 1 Dec 97
Dump Setup                                  Legg, finalize by 1 Dec 97
CW Setup                                    Legg, 1 Dec 97

Emittance Growth from CSR

Tomographic Phase-Space Map                 Piot, 1 Dec 97?
Back Leg Thread                             Douglas, 1 Dec 97

Thread Beam around Machine, Top-Level           Douglas, 1 Dec 97