SiD geometry, magnets and masks:
Takashi Maruyama reported that
At the earlier meeting with SiD colleagues (J.Jaros, M.Breidenbach, N.Graf) it was decided not to change L* but to move M1 and Lumon by 20cm closer to IP to provide 10+10cm for BPM and warm-cold transition, and to increase the support tube radius to about 26cm to accommodate the QD0 size.
Takashi presented an updated Geant model. The issues of space constraints require more studies. In particular, according to Steve Smith, 10cm would be sufficient for a BPM, but according to Brett Parker, 10cm may be insufficient for cold-warm transition of the large aperture QD0. There is also a question of any possible movers needed for the FD magnets, which would take space. Finally, the SiD wall should have a possibility to slide along the beamline by about 2m, thus we also need to consider the sizes of SD0 and the rest of FD.
Increasing beam size at the dump in 20mrad beamline:
Yuri Nosochkov (reported by Lew Keller) found an optical solution to increase the beam size at the dump window by about a factor of ten, so that the window would not be destroyed by an undisrupted beam. This is achieved by lengthening the beamline by about 150m and removing the final doublet in the extraction line. The increased beam size would provide passive protection of the window and rastering ("painting") of the beam would not be needed in this case.
ANSYS simulations of the dump window:
Eric Doyle made simulations of the beam dump window with ANSYS and reproduced ZDR results in terms of temperature difference across the window and temperature in the steady state regime when the window is cooled by water. Next step would involve calculation of transient regime -- increase of the temperature and stress during passage of the train.
The group then discussed various issues of the dump design, in terms of choice of the material for the window (e.g. copper may not be optimal, end more strong material could be considered), radiation damage effects, Tritium production, etc. Dieter Walz, who was present at the meeting and described his experience on various aspects of the design, will work on the ILC dump aiming to have the preliminary design by Snowmass.
New ATF2 optics with extended diagnostics:
Mark Woodley presented the ATF2 optics whith extended diagnostic section. This optics use about 7m of additional space and three additional quadrupoles. It has almost ideal diagnostics and skew-correction section, similar to the one we plan for ILC. The bandwidth of this optics was not yet optimized. We also need to consider the post IP beamline, and make sure it has enough length and number of BPMs, since they will determine the accuracy of beam based alignment of the FD. Mark is also continuing to look into "coasting-style" diagnostics section.
Andrei Seryi, 06/07/05