Minutes from US-LET meeting: 2005 Apr 12 09:30 Pacific Time Attending: LEPP: G. Dugan, L. Gibbons, R. Patterson, D. Rubin, J. Smith FNAL: K. Ranjan LBL: A. Wolski SLAC: T. Raubenheimer, A. Seryi, PT, G. White, M. Woodley Recording: PT, SLAC COMMUNICATIONS: All agreed that some appropriate set of websites and pages are required, no clear consensus yet on what constitutes "appropriate." Given the general problem of webmaster availability, it was not felt that having a single website with a single gate- keeper was ideal. At some point a more modern system (a single site where any authorized person may post a file without going through a gatekeeper) will be available, in the meantime a sensible system might be to have websites at each lab which link to one another. In any event, some additional system of communication would also be useful. Mailing lists, discussion boards, and hypernews were all discussed. Whatever solution is selected, even on an interim basis, should satisfy a few criteria: -> ALL postings are archived in an accessible location and format (the BDS mailing list has this property already) -> Unnecessary and unwanted e-mails should be kept to a minimum; ideally, one should get periodic notification of new postings, for example just a list of posting titles, possibly with links (something similar was done for the LCC-note series), but if possible we should avoid a situation in which extremely content- rich e-mails are being frequently delivered to large numbers of people who do not want them. BaBar's hypernews was mentioned as a possible model, but nobody present at the meeting had any experience with it. Communications Action Items: -> Set up LET website at SLAC with some appropriate organization: PT -> Set up websites at other labs (avoid "missing webmaster" problem): TBD (Note that PT also volunteers to make a diligent effort to post on the SLAC LET site material forwarded from other labs; those other labs will have to decide for themselves whether PT constitutes a trustworthy resource in this regard). -> Investigate BaBar hypernews suitability: PT * * * * REPORTS FROM THE LABS: LEPP: Jeff Smith has been working on main linac DFS simulations using TAO and the BMAD library, starting from the TESLA TDR main linac (23.4 MV/m gradient, quad/24 cavities in the front, quad/36 cavities in the back, 60 degree FODO cell) and can reproduce existing simulation studies using equivalent algorithms and lattices. His plans for future simulation studies include: -> Stray fields -- impact of fields on static tuning algorithms (DFS, BA, Kubo). Expect to have some results for PAC 05. -> BPM Resolution: work with undergraduate to understand how this impacts static tuning methods (better resolution gets better emittance, but how much gain for how much BPM improvement?) -> Impact of beam jitter, again with an undergrad -> Ground motion -> Study the "end effect" problem (how to get the emittance under control in the first 0.5-1.0 km of linac). -> Beam halo -- model generation of beam halo in MDR, tracking of same through LET. The latter 2 items are probable topics for Jeff's PhD thesis. Gerry Dugan has identified an undergraduate to join his bunch compressor work this summer, and has been learning how to apply TAO to the problem. He will be working with Lawrence Gibbons on this problem, starting from the studies performed by Andy Wolski and PT. FNAL: Kirti Ranjan and Nikolay Solyak have been using the US-TOS lattice (28 MV/m, quad/24 cavities spacing throughout linac) and looking at 1:1 and DFS, and have reproduced the results from the LCC-note on cold vs warm static tuning. Kirti will be reporting on emittance dilution sensitivity to the amplitude of various errors at the APS meeting; this work will be ready to present at our next US-LET meeting. Further directions in main linac studies were discusssed, with a recommendation that the FNAL team begin studies to develop an optimal lattice strength vs energy scaling for use in the baseline. LBL: Andy Wolski has produced decks for 7 bunch compressors: a single stage BC which compresses from 6 mm -> 0.3 mm, and 3 other compressors (two 2-stage and one 3-stage) which can compress from 6 mm -> 0.3 mm or from 6 mm -> 0.15 mm. He has completed studies of their emittance dilution for on-axis beams, emittance dilution for 1 sigy offset, IP longitudinal sensitivities to MDR extraction phase, BC RF phase, BC RF amplitude; as the decks are complete, some measure of length / cost is also available for each system. SLAC: Andrei Seryi is working with the BDS team to develop fully-realized BDS designs for 2 mrad and 20 mrad crossing angles, including all the detector, solenoid, and extraction issues. PT has been working with Andy Wolski on the BC studies, with a focus on the transverse emittance sensitivities of the 7 systems. Glen White has been performing full time-domain simulations including e+ and e- main linac and BDS, the beam-beam interaction, and bunch trains; he's using the TDR linac and BDS, and also the TDR linac matched to the ILC IR1 BDS; he's working with a physicist at Daresbury to model collimator wakefields in such a way as to add them to his simulation; Mat-Merlin now has a manual. * * * * NEW BUSINESS: There was discussion of the overall layout of the ILC: where is the MDR as compared to the location of the linac, etc. This is a very rich topic, and it was agreed that this was something good to discuss more fully in our next meeting (a presenter will be identified). Where is the actual boundary between BDS and LET? One can fairly simply select a boundary in the machine between the LET and the main linac, but specifying a conceptual boundary (ie, "Is this task more a BDS task or an LET task?") is harder. It may not even be strictly desirable to have a hard-and-fast treaty point in the work, as long as the two task forces are not duplicating effort. * * * * AGENDA FOR NEXT MEETING: -> Main linac emittance tuning parametric study: Kirti Ranjan, FNAL -> Options for overall layout: TBD