Next Meeting

Date: 26 Jun 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
Status of Lasing Activities                             Neil           20 min
Overview of Injector Setup Procedure                    Biallas        20 min
New Issues                                              All             5 min

This Week's Attendees

J. Bennett, S. Benson, G. Biallas, J. Bisognano, C. Bohn, J. Boyce, R. Evans, J. Fugitt, A. Hofler, C. Hovater, K. Jordan, R. Li, L. Merminga, G. Neil, P. Piot, J. Preble, R. Walker, B. Yunn

Closed Action Items

• Walker: Work with Operations Department to develop requirements for an FEL Alarms Handler software page for use in monitoring the FEL from the MCC Control Room.
  Status: Based on the Alarms Handler for the CEBAF machine and being able to substitute the appropriate signal names, A. Hofler has agreed to start on the FEL Alarms Handler. She needs the EPICS names, definitions, and screens for those systems that are different than the CEBAF machine. (See "New Action Items" below.)

Items of Discussion

This week, having fulfilled the necessary condition of everyone pulling together and working hard, and the sufficient condition of having God's providence, we lased big-time. We lased Monday at low power, and on Wednesday at 1250 we achieved 100 W cw at 4.95 µm. Ultimately that same day we achieved 155 W cw briefly and 150 W cw stably, running at the latter power level for a time approaching an hour. The whole machine ran stably. We probably broke the 100 W milestone Tuesday, but as we later discovered, we fried the first mirror in the optical transport system that sees the light coming out of the optical cavity, and therefore we couldn't get all the power upstairs. So, Wednesday morning we put the power head directly in the mirror can so we could measure the power coming out of the optical cavity. New, better mirrors are on order and scheduled to be received here on Monday, 22 Jun 98. We of course ensured the Laser Safety Operating Procedure for the FEL Optical Control Room, as well as its Laser Safety System, were completed to let us lase safely. [Addendum added at 1520, 19 Jun 98: The damaged mirror was rotated, but a significant area of damage still remains in the laser beam path. Notwithstanding the crummy mirror, at 1510 we had 116 W cw upstairs in the Optical Control Room (!), and the cw run was continuing.]

The machine is amazing. It is hard not to lase, especially once lasing is started, and it is easy to turn on the lasing process. We lase easily even with 2 Hz pulsed beam, and this means we will be able to insert viewers all around the machine and look at the beam profile anywhere with lasing turned on. One benefit, for example, is that we can visually stuff beam through the apertures of the recirculation loop as we commission it, and we can look at the decelerated beam in the energy-recovery dump line. This should make commissioning the full machine much easier than we had thought. We can provide both pulsed and cw beam to users as they desire. We also clearly see lasing harmonics as high as the 11th harmonic. There is so much to learn. G. Neil collected a wealth of spectral data yesterday (18 Jun 98), which he presented at today's meeting, and of course more measurements of the lasing process will be forthcoming as we optimize the FEL. The potential of the machine is not yet known. Every indication is that the wiggler coupling efficiency is enormous, possibly of order 1.5% as compared to the anticipated 0.5%. The quality of both the wiggler and the electron beam is impeccable. We will know more (and with more accuracy) in due time.

Having achieved our key milestone, the commissioning philosophy now shifts, and this meeting was mostly dedicated to planning near-term and mid-term activities. C. Bohn reminded everyone of the MUST priorities for this fiscal year: (1) lase at >100 W cw (done!!), (2) do first user experiment, and (3) take initial data on coherent synchrotron radiation (CSR). We will do all of these and probably more. To be specific, we will fold in the commissioning of the remainder of the machine as we achieve all of the MUSTs. Summer plans fall into the following categories:

• understand and optimize the FEL
• set up and conduct first user experiment
• take beam through first recirculation arc (for CSR measurements) and beyond

The group formulated a list of near-term tasks, and they are as follows:

• measure x-ray production from Thompson back-scattering
• do electron-beam energy scans while lasing
• do optical-cavity-length scans while lasing
• improve the injector setup
• install, commission, and use Happek #1 (located at cryomodule entrance)
• do rf studies in the presence of high-current electron beam
• do RadCon survey outside the FEL Facility with 1.1 mA beam on
• recommission the buncher water skid for higher power
• install and commission pyroelectric detectors for monitoring bunch length
• commission the autocorrelator
• take beam around the first recirculation arc

The general pattern that suggested itself is to do diagnostics and CSR studies on owl shifts, machine development on day shifts, and lasing experiments on swing shift (for which a CEBAF operator will generally be essential!!). Consequently, the two-week scheduling board will generally reflect this pattern starting next week. It is posted on www at http://www.cebaf.gov/accel/fel/documentation/feldoc4/feldoc4-6.html. As shown there, shift assignments for the next two weeks, modulo localized deviations for which affected individuals are already informed, are:

 

   24-26 Jun 98:         Owl -- machine hot, no electron beam
                         Day -- Biallas, Yunn (standby), 1 CEBAF operator
                         Swing -- Benson, Siggins (standby), 1 CEBAF operator
   29 Jun- 3 Jul 98:     Owl -- Evans, Piot (standby), 1 CEBAF operator
                         Day -- Merminga, Walker (standby), 1 CEBAF operator
                         Swing -- Oepts, Krafft (standby), 1 CEBAF operator

New Issues

None or everything mentioned above, depending on one's perspective.

New Action Items

• FEL WBS Managers: Provide A. Hofler with information needed for FEL Alarms Handler: EPICS names, definitions, and screens for those systems that are different from the CEBAF machine.

Old Action Items

• Benson: Generate software-requirements document for limiting the use of viewers in the wiggler region and submit it to the Software Group.
  Status: Overcome by lasing. (due 23 Jun 98)

Test Plans in Work

To match plans discussed above, numerous test plans will need to be generated. As a general rule: No test plan, no beam! L. Merminga provided Bohn with a list of test plans she will be writing for rf studies scheduled for the week after next.

Procedures in Work

Emittance Growth from CSR

Tomographic Phase-Space Map                 Piot, 30 June 98
Back Leg Thread                             Douglas, 30 June 98

Procedures Needed for Recirculation

Thread Beam around Machine, Top-Level           Douglas, finalize 30 June 98
RF Stability during Energy Recovery             Merminga, 30 June 98

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

V.      Finalize "Injector Setup" Procedure                     Yunn/Biallas

VIII.   Establish Expected Beam Quality                         Yunn
        F.      Emittance at 2G02                               (with Li)
        G.      Momentum Spread at 2G02                         (with Li)

IX.     Complete Diagnostics Procedures and Training            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

X.      Develop "Injector Rematch" Procedure                    Biallas/(Unk. Physicist)

XIV.    Update (as appropriate) "First Light" Procedure         Benson