Minutes of 114th FFIR/BDSIM and 36th ILC-Asia WG4 meeting on 8/3/2005
ILC Asia WG4 : Minutes of 36th meeting
August 3 10:00
Rm.425 bldg.3 at KEK.
(1) ATF2 proposal, by T.Sanuki
As announced, all the comments and corrections have been received except for one section of "Beam Diagnostic (word file by S.Kuroda)" by end of this July. He is converting the word-file to Tex, and also checking the references. It will take a week to finalize the proposal. Since the publication process is ready to submit the proposal to the KEK library, it will be submitted in next Monday.
(2) Shintake monitor, by T.Suehara
Some of the packages, which have been received from SLAC, were unpacked at university of Tokyo. Suehara checked a possibility to exchange the mirrors for half wavelength (532nm) on the monitor. It seems to be possible. All the packages will be checked.
He continues to study the background by simulation (GEANT4). Since the beam divergences are maximum at the final doublet, the beam halo will hit the beam pipe at downstream of IP. He estimated the angular and energy distributions of the bremmstrahlung photons at the beam pipe with the incident angles of 0.1 to 1m radian to model the angular divergence in the doublet. He feel that the beam-halo must be collimated at upstream.
(3) Longitudinal space for BPM installation, by Y.Honda
( transparency, pdf, 1 page, 44KB )
Honda talked to the magnet group (R.Sugahara et.al.) on the SUS magnetic effect in the magnets, where the bellows and flanges are made of SUS. The magnet group requires any SUS material to be away from the magnet in distance of twice the magnet-aperture at least.
So, any flange must be located at 80mm from the magnet as shown in a figure. assuming the beampipe diameter is 32mm. If every magnet has a Q-BPM at the upstream side, the standard distance between two magnets is estimated to be 300mm, where there is a 100mm long bellow and the Q-BPM of 120mm length. At the proposed ATF2 optics, the distance should be 250mm except for the final Q and sextupole magnet. To reduce the distance from 300mm to 260mm, he suggested two configurations called as "irregular" for the downstream Q-BPM and "bellow included BPM".
There was a question on the distance, i.e. why the twice is necessary, while just an aperture seems to be enough. Also, the length of bellows must be optimized with necessary movements for the movers, which depend on the alignment and feedback performance, while this 100mm length is the present one used at the ATF extraction line. So it can be shorter. Most of adjacent magnets to the Q-magnets are sexupole magnets. So, can we put the bellow inside the sexupoles ?
The distance between the final Q and sexupole is 100mm. One solution is to make the sexupole with large aperture for enough space of magnet movements on the movers.
These questions will be asked the magnet and optics groups, i.e. to R.Sugahara and S.Kuroda, respectively.
(4) Radiation safety at the ATF2, by N.Terunuma
( transparency, pdf, 1 page, 952KB )
Terunuma talked to the radiation-control people on radiation safety issue at the ATF2 based on the baseline layout around IP as shown in a figure. They suggested that there should be additional space of about 1m length between the 2m-thick concrete shield and the beam dump. Major concern is that the dump is very close to public area outside of the assembly hall, where there is free from the radiation control. In the public area a tolerable dose is 0.2uSv/h, while it is 20uSv/h in the assembly hall.
Also, an interlock system must be needed for a failure of bending magnets. In addition, radiation level at downstream of the 2m thick concrete shield must be evaluated by simulation under various beam conditions which are expected at commissioning time as well as normal operation at the ATF2.
(5) ILC-WG4 plan at SNOWMASS, by T.Tauchi
Tauchi introduced the agenda which A.Seryi has distributed to the BDS mailing list. the message can be obtained at a URL of http://ilcphys.kek.jp/mail/archives/bds/200507/msg00021.html . Also, he introduced the BDS-BCD draft which is available at a URL of http://www-project.slac.stanford.edu/ilc/acceldev/beamdelivery/bds_bcd.htm . We would like to review the baseline choices at next meeting.