Free Electron Laser Commissioning/Diagnostic Meeting

Tuesday, June 4, 1996
Recorder: G. Krafft

Next Meeting


Date: June 11, 1996
Time: 3:00 - 4:00
Place: Test Lab Conference Room

Attendees


D. Douglas, G. Biallas, J. Denard, C. Bohn, R. Legg S. Benson, K. Jordan, G. Neil, and G. Krafft

Items of Discussion


New Items


Between cavity coupling: there is a proposal to enlarge the aperture between cavities in the cryomodule from 1.9" to 2.0". It needs to be checked that the old coupling instabilities will not arise if this proposal is allowed. B. Yunn will check the coupling and old results at Bohn's request. Active item under Yunn's name is activated.

Synchrotron Light Monitor plans: no meeting occurred. It was emphasized that this issue should be dealt with expeditiously. Krafft felt scolded. A meeting with Denard, Piot, Jordan, Benson, Krafft, and Bohn should be scheduled.

Bob Legg presented his plans for an IR viewer for the ITS beam dump. There were several questions that arose. First, J. Denard expressed reservations about the safire window in the high radiation environment. This was dispelled by Legg and others, but Legg agreed to check once again. It was also stated that the IR camera would be more generally useful; it was agreed that a meeting to discuss the camera to buy and the best way to coordinate camera usage was appropriate. Legg, Krafft, Bohn, Jordan, Shin, Neil, Benson, and Denard at least, should be involved.

The lion's share of the meeting consisted of continuing going through the summary of the wide BPM meeting. The meeting produced consensus that such BPMs are useful (we want them), they cannot be reliably used for dispersion measurements when the beam is transversely large, we will use them for steering because we need the positions within the dipoles, and that they are probably not useful for locks downstream of the wiggler because of the effects of laser startup on the beam. This has the attendant consequence that there must be a BPM for energy lock in the first chicane (i.e. before the wiggler).

Most of the rest of the meeting was spent in a non-convergent discussion on various issues associated with autosteering. Things like number of BPMs to autosteer machine, software availability (Bohn will be scheduling a planning meeting with White and Watson soon), software capability or lack thereof, and SLM inputs were discussed. It was debated whether we needed autosteering at all. At the end, it was agreed to allow Bohn to try to interact with the relevant inputs and try to come up with a plan. We will try to schedule this next week.

Finally, on the issue of viewer light generated photocurrents, Sinclair, Jordan, and Benson all agreed that Kevin's idea to use camera illumination by IR LEDs was a good one. They emit at wavelengths above 960 nm, and will not generate photocurrent. This solution has been tested successfully. It was agreed that furthur documentation (i.e. beyond this note in the minutes) was unnecessary, and the issue is completely closed.

Action Items


A-03 No documentation confirmation as of 4/9/96.
A-19 We hope to have a preliminary version of the documentation tree (hierarchy) posted next week. Please take pot shots at it as appropriate.
A-21 Jordan agreed to present a plan for diagnostics reviews on 6/18/96.

First Cut List of Commissioning Tasks


The following list was started for commissioning the Injector Test Stand by D. Kehne and G. Krafft. It is only a first cut and should be added to and modified through e-mail to G. Krafft. The list is a partial answer to the question: what does it mean for the Injector Test Stand to be done?

C-1     RF gradients verified
C-2     Operational RF phases determined
C-3     Drifts (of phases if like main machine) quantified
C-4     Gun current verified/operational procedure complete
C-5     Beam jitters determined
C-6     Cryounit Focussing/Convergence determined
C-7     High power CW beam is delivered for ``awhile''
C-8     Cathode lifetime studied
C-9     Engwall/Kehne studies on gun transverse/longitudinal emittance complete
C-10    PARMELA ``verified''

After the move to the FEL building the following tasks must be completed to prepare the beam for injection into the linac.

C-11    Transverse phase space at injection verified
C-12    E-beam matched at injection point
C-13    Longitudinal phase space verified
C-14    Longitudinal tilt checked at injection
C-15    Above determined at high power

Action Items (assigned)


A-01	Update Drawing                                Bohn                weekly
A-02    Viewer light photocurrent                     Benson, Jordan    complete
A-03    Stray fields in test stand                    Legg              complete
A-04    Unit gradient precision                       Bohn, Liu
A-05    Injector energy precision                     Douglas
A-06    10 MeV dump optics                            Douglas
A-07    Bypass optics                                 Douglas
A-08    M56/RF phasing and beam load issues           Neil, Douglas, Liu
A-09    Dump Instrumentation                          Legg               6/04/96
A-10    Back leg diagnostic placement                 Douglas
A-11   	Multifrequency CSR Measurements               Krafft             6/04/96
A-12    How should the path length be checked?        Krafft, Jordan     6/11/96
A-13    Impedance Layout for Wiggler                  Yunn, Neil        complete
A-14    Reduce M56 to under 30 cm                     Douglas           complete
A-15    Commissioning Procedure                       Legg, Krafft       5/16/96
A-16    Average Current Measurement/Assess Far. Cup   Legg
A-17    4-Channel BPM on the IRFEL                    Bohn, Denard
A-18    Trombones                                     Douglas, Krafft
A-19    Web Documentation                             Krafft              weekly
A-20    10->42 MeV dump                               Biallas
A-21    Diagnostics reviews                           Jordan             6/11/96 
A-22    Beam dump and scaper design                   Wiseman            6/18/96
A-23    Ganged powering schemes                       Douglas
A-24    Beam loss                                     Bohn
A-25    Synchrotron Light Monitors                    Krafft
A-26    IR Camera Plan                                Legg
A-27    Autosteer Plan                                Bohn
A-28    Cavity Coupling                               Yunn

Action Items (pending)


P-01    Determine Beam Pulse structure for setup
P-02    Laser phase modulator
P-03    Slit emittance measurement
P-04    Is an energy compression scheme needed?
P-05    Devise fine-tuning procedure for buncher gradient
P-07    Diagnostics "Freeze"
P-08    How do we change energy? What is the energy range?
P-09    Do we need bunching after the module
P-10    Will the SLM monitor work to center the large beam
P-11    Calculate from Hall C data how much scatter the BPMs can take
P-12    FEL/OTR interaction question
P-13    Do we have sufficient diagnostics for emittance degradation measurements
P-14    How is the gun/laser operated?
P-15    Discussion on robustness of controls??????
P-16    Injector diagnostics in the main machine
P-18    Technote by Yunn summarizing machine impedance
P-19    Consistent linac/bunching phase sets
P-20    Lock plans (who in particular)
P-21    Save/restore plans
P-22    FSD plans
P-23    Transverse Effects in CSR
P-24    FEL Commissioning review
P-25    RF control sensitivities/Microphonics Diff for FEL/Pathlength effect
P-26    What if studies
P-27    Plan to measure beam loss
P-28    Scrapers: Where and How?
P-29    FEL/linac interaction
P-30    Tracking including realistic wiggler fields
P-31    What drives the vacuum spec.
P-32    Are two sextupole families enough to tune M56
P-33    Is path length feedback needed?
P-35    Coordinated ITS beam running/SRF commissioning plan
P-36    Beam power robust BPMs
P-37    42 MeV dump design and interlocking

Agenda for Next Meeting


         Item                           Person Responsible   Time
         ----                           ------------------   ----
* Review agenda/corrections to minutes       Krafft	     5 min.
*   New drawing                               Bohn           5 min.
*   New issues
       IR Camera Plan

*   Autosteering                              Bohn           5 min.
*   SLM Power and Cameras                     Piot          15 min.
*   Web documentation                        Krafft         10 min.
*   Active item discussion                    All           10 min.
*   Agenda for next meeting		      All	     5 min.