Free Electron Laser Commissioning/Diagnostic Meeting

Tuesday, May 14, 1996
Recorder: G. Krafft

Next Meeting


Date: May 21, 1996
Time: 3:00 - 4:00
Place: Test Lab Conference Room

Attendees


D. Douglas, L. Merminga, G. Neil, G. Biallas, S. Benson, D. Kehne, and G. Krafft

Items of Discussion


New Items


Requirements and reviews for diagnostics; especially new ones. Jordan agreed to come up with a plan that can be discussed in the next few weeks. The plan will have due dates for requirements, reviews (if re- quired!), and prototypes. There was broad agreement that this was a good way to procede.

Shielded viewers. No action, however, Sinclair has wondered why the first viewer in the ITS is shielded given the large bunch length there. Not clear at the moment how to get his concerns addressed. Pending.

Extra dipoles for the 10->42 MeV dump. No action, but Biallas will get the drawing updated.

Slit design. This came up again at the Tuesday meeting. The best plan presented was to have D. Kehne forward what's known about the UCLA design to Wiseman, so he can at least get some idea how to get started. More detailed planning and calculations related to the performance of the device will have to wait greater availability in Kehne's time; the soonest he was willing to consider was the middle of June, partly because he's not sure what the scope is. In other words, this item will remain a pending item as it has been for two months.

42 MeV dump design and interlocking. Krafft forwarded messages received from Sinclair on the fact that the current injector dump won't work at 600 muA. Biallas volunteered that Butch was probably available to start detailed design work given some guidance. Krafft will try to recruit Sinclair to help. Also, it was pointed out that T. Smith at Stanford has a dump with the right parameters.

Action Items


A-01 No specific changes indicated. Douglas intends to make some changes however.
A-03 No documentation confirmation as of 4/9/96.

A new potential problem is photoemission in the gun by background light in the cave, especially by things like viewer lights. After a short discussion, Jordan and Benson agreed to look at the problem. Potential solution mentioned was to filter the illumination light so that no photoemission is generated. An active item is added.

Optics and J. Flanz visit: Douglas gave a summary of the visit, including especially a admonition from Flanz to have good phase space measurments available to get the job done quickly. Given the experience with the main machine, this seems wise counsel.

The final item of discussion is a long pending item, namely organization of documentation, especially Web documentation. Krafft presented a preliminary tree based idea. The group seemed convinced that this approach might save us headaches in the future. It is probably better to get this done sooner rather than later because our initial documentation might be also organized relatively painlessly now; it gets more difficult the longer one waits. Krafft, Niel, and Jordan will meet to try to come up with a preliminary tree two levels deep; we will try to get something on the web that people can take potshots at in the next few weeks. T. Oren has been consulted on some of the details. A previously pending item was made active.

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             4/16/96
A-02    Viewer light photocurrent                     Benson, Jordan   
A-03    Stray fields in test stand                    Legg  	       complete
A-04    Unit gradient precision                       Bohn, Liu        4/16/96
A-05    Injector energy precision                     Douglas          4/09/96
A-06    10 MeV dump optics                            Douglas          5/14/96
A-07    Bypass optics                                 Douglas          4/30/96
A-08    M56/RF phasing and beam load issues           Neil, Douglas, Liu
A-09    Dump Instrumentation                          Legg             5/23/96
A-10    Back leg diagnostic placement                 Douglas          5/30/96
A-11    Multifrequency CSR Measurements               Krafft           4/30/96
A-12    How should the path length be checked?        Krafft, Jordan   4/30/96
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     4/30/96
A-18    Trombones                                     Douglas, Krafft  4/09/96
A-19    Web Documentation                             Krafft
A-20    10->42 MeV dump                               Biallas
A-21    Diagnostics review                            Jordan

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-17    Gang of power supply for backleg quads
         (must include emittance meas. capability)
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
*   Task List Discussions                         All           30 min.
*   Agenda for next meeting                       All            5 min.