LET: Meetings: Minutes for 2005 May 10

Attending: Representatives from LEPP, FNAL, LBL, and SLAC

Reports from the Laboratories:

Cornell: Jeff Smith has studied BA, DFS, and Kubo's Method for emittance control, with and without an external DC field (the Earth's field as measured in Ithaca, NY was used in the study); this work will be reported in a paper at PAC next week. Jeff modelled the linac as having zero field in the RF cavities and a constant field in the quad and drift spaces (since the RF cavities are shielded). This led to an interesting question: how effective is the shielding for the RF cavities? SLAC's experience with attempting to shield the linac in the 1960's was not very good (the remnant field in the shielding material was at least as large as the earth's field). Understanding just how good the shielding of the RF cavities is would be worthwhile research.
FNAL: Kirti Ranjan is doing a study of 30 MV/m main linacs with a variety of quad spacings (both uniform throughout the linac and non-uniform), and looking at the performance of DFS (which may differ from the performance of 1:1 steering reported here). Results soon.
LBL: Andy Wolski reported that the bunch compressor study was converging on a recommendation for the baseline, to wit: a 2-stage solution which could be tuned to have either 2 90 degree phase rotations or 1 such rotation. The former configuration is better for emittance preservation, the latter is better for protecting the IP from damping ring phase and bunch length instabilities. The next step in the study will be to look at the best way to design a BC which accomodates both of these configurations, can reach bunch lengths as low as 150 um RMS, and makes optimal use of installed RF cavities. The current status of the BC study will be reported at PAC.
SLAC: PT reported on efforts to build a "scarecrow" ILC lattice which would include properly matched decks from the BC to the IP, and would encompass all the configurations listed in the ILC parameters document (various gradients, bunch lengths, final energies, LCD solenoid on or off). The idea would be to have a reasonable lattice for initiating start-to-end (S2E) simulations, with the understanding that more complete decks will be issued once the decisions which are needed for those decks are made. There is also an effort underway to define a set of tasks for the baseline and the CDR, information is available here. Marc Ross reported on research into using the HOM signals to derive beam position information, and concluded that resolution at the level of 1 micron was achievable; this will be reported at PAC.

Old Business: No items of old business were discussed.

New Business: Three items of new business:

Tom Himel's availability study is investigating the parameters of a "keep-alive" conventional positron source, which would operate when positrons from an undulator source are not available. He would like input from LET on the sorts of beam tuning operations which we foresee, and some insight into what sort of positron beam (charge, rate, quality) would be needed. He would like this input on the timescale of the next 6 to 8 weeks.
Marc Ross will convene a "brainstorming" meeting on MPS in the next few weeks. The goal is to begin work on a quantitative list of all occurrences which could cause accelerator damage within a single train or even single bunch at nominal charge density. The goal is to have a complete catalog of all such failures by Snowmass, and to have sufficient quantitative information to begin studying mitigation (ie, for mitigation it matters if the MPS tolerance on a component is 1 part per million or 1% -- we need to have all those sorts of quantities in hand by Snowmass).
The Laser Wire group would like input from the LET taskforce on how we would foresee using laser wires in the ILC, so they can focus their R & D effort.

Next Meeting: Tuesday, 24 May 2005, 12:30 / 11:30 / 9:30.