Minutes of 103rd FFIR/BDSIM and 25th ILC-Asia WG4 meeting on 4/27/2005

ILC Asia WG4 : Minutes of 25th meeting

April 27 10:00
Rm.425 bldg.3 at KEK.

(1) ATF2 commissioning

Following the discussions at the previous meeting, the experiences of FFTB commissioning have been asked to SLAC. Dr. Peter Tenenbaum (PT) kindly replied as this. Therefore, we need a "4um" carbon wire scanner or a laserwire system instead of Shintake monitor for commissioning. Also, a section of "strategy for the commissioning beam" might be needed in the ATF2 proposal.

(2) Q-BPMs and Q-magnets

The PAL group will visit to KEK for 8 through 10 May, 2005. We will discuss on the basic design of Q-BPM with 100nm position resolution and detailed schedule of prototype and mass production during this visit. A sketch of Q-BPM on the Q-magnet is provided by Y.Honda. Electronics design was presented at the video meeting with SLAC on 4/28, i.e. next day of this meeting.

Kuroda introduced basic properties of Q-magnets. There are 22 Q-magnets at the final focus system and 5 Q-magnets at the transfer line of the base line design, All the magnets has same length of 20cm and aperture of 32mm diameter, where the beam pipe has inner diameter of 20mm.

(3) Shintake monitor

T.Suehara briefly explained status of the shipment from SLAC and estimations of signal and background.

The shipment was prepared by T.Sanuki and T.Okugi with help of D.McCormick and M.Ross at SLAC for 26 through 29 April. The arrival will be in middle of June.

At ATF2, the signal yield is estimated to be order of 104/bunch with the maximum photon energy of 28MeV. Possible background would be synchrotron radiation, bremmstrahlung photons by collision with beam and residual gas in beam pipe and also by collision with the beam-halo and beam pipe, and back-scattered radiations from the beam dump. Since the typical critical energy is about 1 KeV, the synchrotron radiation must not be background at the Shintake monitor. The background from the dump can be discriminated by timining so that a distance between the monitor and the dump is important parameter; i.e. a few m distance may be preferred. In order to estimate the radiation and the optimal distance from the dump, an experimental study will be conducted in next ATF run; i.e. a week of 16th May. The most severe one might be the bremmstralung photons with the same timing as the signals. At FFTB/SLAC, beam collimation has been essential in order to suppress the background produced by the halo. Therefore, we would like to estimate the halo at the ATF extraction line. The ODR experiment could have some information on the halo, and the wire scanner can measure the halo in principle with higher sensitivity of the detector. Such possibility should be investigated.

(4) discussion on plan for SNOWMASS

At the first ILC workshop on November 2004, the WG4 decided that two crossing angles of 2 and 20mrad are the strawman schemes. However, at the MDI workshop on January 2005, Y.Iwashita presented an idea of RF kicker to provide a headon collision. Since then, the hardware R&D on the kicker has been initiated by him. There is potentially a desire of headon collision in experimentalists for simple experiment with the minimum veto angle. So, we would like to support this headon scheme. Recently. it is proposed that we should prepare the optics design (SAD or MAD dec-files) of all the crossing angle schemes and ILC-Asia WG4 is expected to contribute on this effort. The short term goal is the presentation at the BDIR workshop ,London, 20-23 June. Finally, the full discussion shall be at SNOWMASS to choose a baseline design. At KEK, it seems to be difficult to find a person to study the headon optics design. Therefore, we would like to ask Dr. L.Keller (SLAC) for the further study, who has investigated the extraction beam line with the headon scheme collaborating with Y.Iwashita. We could contribute the estimation of background from the extraction line by the BDSIM, etc. .