Minutes of 100th FFIR/BDSIM and 22nd ILC-Asia WG4 meeting on 4/6/2005

ILC Asia WG4 : Minutes of 22nd meeting

April 6 10:00
Rm.425 bldg.3 at KEK.

(1) ATF2 proposal

The editorial board (Sanuki, Andrei and Blair) discusses on the executive summary which is also the PAC05 paper. A chief editor will be selected among them for the PAC05 paper.

(2) Bunch compression system

At the previous meeting, Vladimir pointed out that no bunch compression is needed since the updated IP-BPM design has enough sensitivity to "2nm" position resolution even with the large beam divergence (his talk).

Honda will report the angular jitter (as well as divergence) effect on the resolution at the next meeting.

Kuroda introduced Pivi's talk on the bunch compression system consisting of a chicane sandwiched between two RF cavities of S and C-band. The energy spread is inversely proportional to the bunch length in his design. However, Yokoya pointed out that a non Gaussian tail in the compressed beam must create significant background for the Shintake monitor. So, aperture must be wide enough for the "1%" energy spread.

After discussions, we finally agreed that the baseline design has no bunch compression because of the background issue and limited space as well as saving the budget.

(3) ATF2 layout in the assembly hall

As you realized Kubo's e-mail, the piping system of the KEKB crab cavity R&D might not move in March 2006 when the floor construction starts. The crab cavity R&D plan already delayed the schedule in a few months. At present, two cavities will be installed in the KEKB-ring in February 2006. Immediately after the installation, we will know whether the piping system can move to the STF area.

So, at today's meeting, we agreed that we make a baseline design with no interference with the KEKB crab cavity area and an optional(ideal) design of the straight beam line adding a Mark's 10m long coupling correction section. Apparently, the baseline design can not have additional space for the coupling correction. Both beam lines must keep off the piping system (blue area in the figure) and the RF gun area both with 3m open space for concrete shield. No bunch compression system is considered in both designs.

Kuroda will make these designs consulting with the optical design group by the next meeting. Also he ask Araki-san for drawing the layout in the assembly hall.

Kubo will ask Mark for simulation of the coupling correction under the present condition at the ATF extraction line. Mark' talk can be found on this home page ( ILC-BDS at SLAC) .

When the beam line increases in length close to the assembly hall wall, the beam dump must be thicker than the present one of 3m thick concrete. Kuroda (Terunuma) will ask radiation safety group for the necessary thickness, where the beam dump must be 3m apart from the wall. Also, Tauchi (Urakawa) will estimate additional cost for the extension by the next meeting.

(4) 5mm diameter beam pipe at IP for IP-BPM

We would like to finalize the design of IP-BPM for construction ready. Therefore, we would like to confirm that the 5mm diameter beam pipe at +/- 20cm around IP has no problem on the ATF2 beam. We know that Andrei asked K.Bane for the evaluation. However, we has no answer. So, Tauchi will ask Andrei for the answer. With this positive answer, Vladimir can initiate the final design. He will complete the detail technical design within 2 months, i.e. by June.