LET: Meetings: Minutes for 2005 September 13
Attending: Representatives from LEPP, FNAL, and SLAC
Ongoing Work since Snowmass:
Jeff Smith (LEPP) and Kirti Ranjan (FNAL) are performing comparisons of their 1:1 and DFS algorithms for nominally identical ensembles of misalignments and errors. Jeff's emittance growths are larger, but he does not observe "spikes" in the emittance vs S curve when averaging over 100 seeds (individual seeds have spikes, not the average); Kirti does see such seeds. Work is ongoing with Daniel Schulte (CERN). Other differences: Jeff uses BNS damping, Kirti does not.
Jeff is also looking at spin rotators for 5 GeV beams, starting from the Emma and TDR designs. There are plans afoot to add spin tracking to the beam-beam codes such as GUINEAPIG; does BMAD need this as well?
Nikolay Solyak (FNAL) is studying tuning bumps and finds that they help a lot; he will report on this and on adaptive alignment at the next meeting. He finds that wire scanner precision worse than 10% is a serious problem for bump tuning. ATF's laser wire achieved a 2% precision but the measurement takes a long time; Marc Ross (SLAC) expects about 5% precision with the linac installations. G. Blair wrote a note on this for EuroTeV last summer.
Marc is also looking at laser wires in the spin rotator area and cold linac. He is interested in using the wires to perform a "4-D emittance" calculation (ie, to measure the normal-mode emittances and coupling terms directly; standard techniques only measure the projected emittances). Previous attempts to perform this measurement have not been successful -- essentially the fit becomes ill-conditioned if the emittance ratio is large and the measurement precision is anything larger than miniscule. He is also looking at performing xy coupling measurements with cavity BPMs.
PT (SLAC) is making improvements to Lucretia: a better transfer map for sector bend magnets, addition of crab cavities, and a few bugfixes. Marc noted that Karl Bane wrote a TTF note a few years back on multibunch issues for crab cavities.
Old Business: None.
New Business: There is some concern about the positioning of the e+ production undulator in the ILC baseline design. The choice of position impacts tuning, MPS, and many other issues.
Next Meeting: Tuesday, 27-Sep-2005, 12:30 / 11:30 / 9:30.