Free Electron Laser Commissioning/Diagnostic Meeting

Tuesday, April 22, 1997
Recorder: R. Legg

Next Meeting

Date: April 29, 1997
Time: 3:00 - 4:00
Place: Test Lab Conference Room
Attendees
---------------

R. Legg, C. L. Bohn, Q. S. Shu, K. Jordan, J. Karn J. Bennett, L. Merminga, A. Guerra, S. Benson G. Biallas, B. Yunn, D. Douglas

Addenda/Errata to Previous Minutes
-------------------------------

  • S. Benson question for B. Yunn - Is the focus at the entrance of the quarter cryounit optimized (it looks very tight)? Yes; apparently this is a misperception caused by looking at Betatron functions vs. sigmas or vice-versa.

  • M. Wisemann sent me mail indicated the X chamber height is about 1.7 inches (?) but could get smaller. This is of interest to the scraping question raised last week.

    Items of Discussion
    ----------------------

  • D. Douglas presented his charts showing propogation of the electron beam around the machine for the 0, 60, and 135 pC cases based on the simulations of Byung. His simulations suggest that the high mismatch points are in the backleg, but still are small compared to the pipe size. The charts can be viewed on the www at:

    www.cebaf.gov/~legg/042297_comm/mismat.pdf
    www.cebaf.gov/~legg/042297_comm/remat.pdf
    (sorry about the orientation - they reflect the views of their sponser)

  • D. Douglas talked about the problems associated with the air core correctors and their "good field" spec. He approached the problem statistically, using the SSC design methods. He stated we haven't done the detailed field error simulations for the lattics and that it will take about 6 calendar months to do them.

  • The bottom line is that a 3% error in the field uniformity for the corrector magnets could translate into a 2X error in downstream sigmas. 1% is probably acceptable but we haven't done the simulations to know how conservative the estimates are.

  • The three proposed methods for correcting the magnets to meet the spec are:
  • Dave pointed out that while option three would work there were places on the machine without the space to insert metal magnets and not have crosstalk between them and adjacent devices. S. Benson related that this had happened on the Duke FEL and adding metal to fix problems can put one on a slippery slope.

  • It was decided that:

    We will abandon metal magnets where cross coupling is a problem (these will be identified by Dave), and pursue the best air core correctors we can measure for those locations. Otherwise we will use option 3). If we can do no better than 3% with the best air cores we can get now, then we may look at a retrofit after we have a better handle on the problem. To that end Dave is to start the simula- tions needed to really quantify the issue.

  • The slides for this talk can be viewed on the www at:
    www.cebaf.gov/~legg/042297_comm/corr.pdf

    New Issues
    ----------

  • Check your snail mail for the ITS shift schedule. All FEL principals are expected to do their part. Found out that the shift times are wrong on the schedule!!! Ops changed back to a straight 8 to 4, 4 to 12, and 12 to 8 schedule to meet demands with the staff available.

    Action Items
    ------------

  • D. Douglas will start simulations to look at gradient errors. 
      
Action Priority  Items (assigned)
----------------------------------

A-05   2  Injector energy precision                     Douglas
A-15   1  Commissioning Procedure                       Legg, Krafft    5/16/96
A-19   0  Web Documentation                                             weekly
A-20   1  10->42 MeV dump                               Douglas
A-24  1,2 Beam loss                                     Bohn
A-29   1  Software Planning for Longer Term             Bohn, et al.
A-30   1  Burnthrough/Conflat Expansion                 Denard, Kloppel
A-34   2  Consistent Linac phasing plan                 Yunn
A-35   1  simultaneous transverse and longitudinal      Kehne/Engwall	8/6/96 
A-39   1  report on ARR plan 				Legg		8/23.
A-42   2  2nd gun for long term tests			Bohn		10/1/96
A-44  1,2 Start Rui on emittance code                   Bohn            8/13/96
A-47   1  OTR beam interaction number by 		Denard		9/11
A-54   1  FEL Turn-On Proc				S. Benson	11/1/96
A-55   1  Laser Diagnostic Proc				Benson		11/1/96

Action Items (pending)
------------

P-02  1   Laser phase modulator						Jordan
P-05  1   Devise fine-tuning procedure for buncher gradient		Krafft/Kehne
P-08 1,2  How do we change energy? What is the energy range?		Benson
P-14  1   How is the gun/laser operated?				Benson
P-15      Discussion on robustness of controls				Legg
P-19  2   Consistent linac/bunching phase sets				Yunn
P-20  1   Lock plans (who in particular)				Johannes?
P-21  1   Save/restore plans						Benesch
P-25 1,2  RF control sensitivities/					Merminga
	    Microphonics Diff for FEL/
	    Pathlength effect
P-29  2   FEL/linac interaction						Merminga
P-30  2   Tracking including realistic wiggler fields			Douglas
P-37  1   42 MeV dump design and interlocking				Wiseman

Agenda for Next Meeting
-----------------------

                Item                              Person Responsible     Time
                ----                              ------------------     ----
    *	Review agenda/corrections to minutes	        Legg	         5 min.
    *	How the rf will go CW				Merminga	 20 min
    *   Milestones for ER test plans			Legg		 20 min
    *	New issues					All		 10 min
    *	Agenda for next meeting		                All		 5 min.