Draft Minutes of Accelerator Physics TS Group Meeting, Aug 16, 2006
1, Static tuning:
(A) BPM Scale error:
K.Ranjan’s study looks consistent with results from CERN, though detailed comparison has not been done yet. BPM scale error 20% RMS (given by Instrumentation Group) will cause problem in static tuning if we rely only on DFS.
Somebody (some others may not) feel 20% is too large.
There was discussion on possibility of calibration.
Experience of Tevatron shows smaller error.
Experience of FFTB, 15% error, suggests 20% may be reasonable.
A. Valishev (?) will investigate calibration methods. Then we should discuss with Instrumentation Group (M. Ross et.al.).
Written (after the meeting) comment by P.Tenenbaum:
One thing about the FFTB's 15% error was that it was systematic – all of the BPMs reported a movement which was larger than the actual movement. We checked this with the mover system, but in principle we certainly could have gotten a better calibration than 15% with dipole correctors as well. There was a comment that SC corrector calibrations are also difficult to do. My suggestion -- use NC correctors in the last part of the RTML. We can certainly calibrate these to 1%, and the linac has almost no filamentation and almost no wakefields; so the oscillation at the end of the linac should match the model prediction rather well.
Even with model errors from quad strength or energy gain uncertainties,
I would guess that we can limit the BPM scale factors to 5%.
(K.Kubo will ask M.Ross for his comments on our discussion.)
(B) BPM resolution:
10 micron, which is written in present BCD, is too large.
1~3 micron will be required.
We probably should ask BC (Baseline Configuration) change. But exact number could not be fixed.
(C) “Nominal misalignment set”:
(Do we agree on the table?)
(D) Bump tuning:
Required accuracy of beam size measurement should be set from realistic simulations.
(Do we already have?)
(E) Writing a document:
We should write a summary of ML static tuning study.
This work is related to writing Accelerator Physics section of RDR.
D. Schulte and K. Kubo agree to start.
2, RTML:
J.Smith will continue to study RTML tuning.
A.Latina will study tuning of Bunch Compressors.
P.Tenenbaum will try to find more people to study.
3, BDS:
G.White will report his work in the next meeting.
People at CERN have started study for CLIC BDS.
4, Dynamic study
Quad position jitter and beam injection jitter will not be problems for DFS tuning.
Feedback system should be designed and the performance should be checked.
(We need to assign someone to be responsible soon.)
Some questions:
Interference between feedbacks at different places and of different kinds?
Stability of lattice function (Quad strength and beam energy)?
Beta-function is too small for post linac FB?
(G.White said much more than this but I could not record. I would like to add his comments, if he gives what he said.)
5, Next meeting
August 29 (Tue.), same time (13:00 GMT).
Using WebEx (I think the system worked well.), no more old video system,
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