Oide1_ART2007

1. 1) Cavity production R&D: The present plan for S0/S1 sets the target of evaluation in FY2009 by producing substantial number of 9-cell cavities. Besides the baseline TESLA cavity, it will be also important to produce enough numbers with alternate shapes or materials such as large grain & single crystal for the evaluation. An international coordination for the partitioning and balance is quite important for this study to avoid unnecessary duplication or not to lose completeness. • 2) The presented plan for the ILC accelerator unit test starts in FY11. I am wondering it is consistent with the schedule of the EDR. Actually similar situation exists in other regions, too. The goal and schedule of the EDR must be discussed. • 3) The newly designed adjustable rf coupler will be an essential component for the rf distribution system. I hope actual production and high power tests including durability will be done soon.

2. 4) Although the beam test for low emittance beam with electron cloud in a dedicated mode at CESRTA or other rings can be interesting, I think more clarification of the goals and methods is necessary. We must take the following issues into account: (a) Such a proposed emittance is only achievable at low bunch current which may not be enough to cause the electron cloud. (b) Since it is not possible to replace all existing beam pipes with ILC-style ones, the formation of the electron cloud will be quite different from the ILC DR. (c) Testing a small piece of beam pipe can be done parasitically in running machines. • 5) The bunch length in the DR might be restored to 6 mm by smaller momentum compaction. If you care the instabilities due to small alpha, a variable momentum compaction lattice may be considered. • 6) The beam simulation in the linac should take the energy calibration error into account at each location in the linac. • 7) Vertical crab effects by the crab cavity should be considered. Also knobs to correct them should be prepared.