Free Electron Laser Commissioning Meeting

Tuesday, 25 Aug 98
Recorder: C. Bohn

Next Meeting


Date: 4 Sep 98
Time: "0845"-0945
Place: FEL Facility Break Room

Agenda for Next Meeting


Item Person Responsible Time ---- ------------------ -------- Status of Open Action Items All 5 min Commissioning Schedule Bohn 10 min Overview of Injector Setup Procedure Biallas 20 min Augmented Recirculation/Lasing Procedure Douglas 20 min New Issues All 5 min

This Week's Attendees


J. Bennett, C. Bohn, D. Douglas, J. Fugitt, A. Grippo, K. Jordan, R. Lauze, G. Neil, D. Oepts, J. Preble, M. Shinn, B. Yunn

Closed Action Items


Items of Discussion


According to the plan for refurbishing the gun, we will be able to resume FEL commissioning on 10 Sep 98. Our focus will be achieving high-power cw lasing with energy recovery, picking up where we left off prior to the FEL Conference. Day Shift and Swing Shift will be oriented toward machine development toward this end, and Owl Shift will continue to be oriented toward diagnostics, and eventually CSR experiments. Today's meeting centered on a discussion of the state of the machine when we turned off 13 Aug 98, with the aim of identifying tasks that have been thus far overlooked or not yet openly discussed. A list of these tasks and principals follows below. From the point of view of beam physics, the most fundamental need is to improve our ability to scrutinize what is happening with the longitudinal phase space as each bunch progresses around the recirculation loop. A considerable portion of the discussion centered on ideas how to proceed based on the longitudinal phase space of the injected and recirculated beams at the entrance to the cryomodule. In conjunction with this discussion, the need arose for "Chebyshev software" for the injection beam-current cavity, and this need is listed below under "Transport". Otherwise, the list itself serves to summarize the essence of today's discussion. Again, it lists tasks that may have been overlooked or had not been openly discussed to date:

Stabilize Drive Laser RF Phase Drift (Shinn):

Improve Drive Laser SHG Power (Shinn):

Instrument Gun for HV Tests (Fugitt/Biallas):

Instrument Cryomodule (Preble):

Instrument Beam Transport (Jordan/Krafft):

Add Software (Grippo):

Augment/Refine Procedures and Get Buy-In (Bohn):

As a final comment, R. Lauze made three helpful points. First, the opportunity always exists for FEL people to sit main-machine shifts (preferably Swing or Owl) with CEBAF operators, thereby observing CEBAF software and methods and possibly gaining ideas for application to the FEL. Second, perhaps the best way to test the integrity of an FEL procedure is to ask a CEBAF operator to implement it and thereby identify problem areas. Third, to assure configuration control, we ultimately will need to develop troubleshooting procedures that explicitly establish limits on machine settings. (Bohn will be draconic in maintaining configuration control when we turn the machine back on -- be forewarned!!)

New Issues


See discussion above.

New Action Items


See discussion above.

Old Action Items


Procedures in Work



Procedures Needed for Recirculation



Unfinished Subsidiary Tasks for Phase Space Metaprocedure


Task                                                           Principal
----                                                           ---------
I.      Stabilize Drifts in Drive-Laser RF Phase               Walker/Fugitt

II.     Calibrate RF Gradients
        A.      Buncher                                        Yunn    
        B.      Cryounit Cavities (fix control screen)         Merminga/Krafft/Yunn
        C.      Cryomodule Cavities                            Merminga/Krafft/Yunn

III.    Reconcile Methods for Setting RF Phase                 Merminga/Krafft/Yunn
        A.      Buncher Cavities
                2.      Minimum bunch length/time of flight
                
        B.      Cryounit Cavities
                1.      Transient phasing
                2.      Cresting
                3.      Time of flight

IX.     Complete Diagnostics Procedures and  Users' Guide      Krafft/Piot
        A.      M_55 #1, #2
        B.      Happek #1, #2
        C.      BPMs
                1.      button calibration factors 
                2.      rotated MEDM spike charts
                3.      difference orbit data acquisition script
        D.      Multislit #1, #2
        E.      Quad/Viewer (at Wiggler, after Wiggler)
        F.      Multimonitor (at Wiggler)
        G.      SLM/CSR
        H.      Zero Phasing
        I.      Momentum Spread (Injector, Linac Pre-Wiggler, Linac Post-Wiggler)
        J.      Energy

XIV.    Laser Turn-On Procedure                                Benson