Minutes of 44th FFIR meeting on 12/4/2002

The meeting was held in a room of 425 at KEK, 10:00-12:00, 12/4/2002. We discussed on beam delivery system(simulation), fast feedback system, collimation system and support tube R&D, etc. . We also discussed on the layout of the extraction line, which should be optimized with careful regard to the incomming FF line and the beam dump with radiation shields.

(1) Simulation on beam delivery system (Tanabe, University of Tokyo)

(transparencies, 4 pages, pdf ,104KB ) He updated the simulation of synchrotron radiations. Assuming the beam has a flat distribution (50 sigma_x, 200 sigma_y) at the entrance of BDS, the spatial and energy distributions of synchrotron radiations have been calculated around the interaction point(IP), where the collimation depth was set to be46 sigma_y x 12 sigma_x. the average energy was 4.76MeV. Since no mask is installed at the upstream of IP, the spatial distribution shows an asymmetry in horizontal direction. The results can be used for optimization of collimation depth together with a design of final quadrupole magnet, especially for the aperture.

Muon background was also simulated. The muon rate going through the detector has been estimated to 1.4 x 10-5 relative to the total number of electrons at the entrance of BDS. The average energy was 61GeV.

(2) Collimation system(T.Ohgaki, KEK)

(transparencies, 5 pages, pdf ,996KB ) He succeeded to combine the JLC collimation system with the Pantaleo's final focus system, where there is a big bend 0f 5.5 mrad. The JLC collimation system is based on the JLC design study ( Oide's nonlinear collimation system). This system can use the muon attenuators although the total length becomes longer (about 2.1km at present). He will investigate further details of this system ( especially for optical corrections) and backgrounds (synchrotron radiations, muons, etc.). He will also try to make shorter the BDS.

(3)Final focus system (S.Kuroda, KEK)

(transparencies, 1 page, pdf ,xxKB ) He studied tolerable errors of field strength of the final quadrupole magnet. This study is primarily for an option of permanent magnet. His result shows that beam size can be corrected within sigma_y(x)<4(350) nm for dk/k < +/- 1% by matching quadrupoles, sextupoles and longitudinal movement of the final quadrupole magnet. Magnitude of the movement is +/- 13mm for dk/k < +/- 1% , whose relation is linear.

(4) Fast feedback system(N.Delerue, KEK)

(transparencies, 12 pages, pdf ,1.9MB ) He demonstrated responses of circuits of simple and delayed models by real BPM signals and available electronics components at ATF. While he succeeded the simple model, he could not get proper "delayed response" with the delayed model. The reason is too weak (attenuated) signal after the delay. Using an available amplifier, signals were saturated. So apparently, an amplifier with lower gain and proper band width should be necessary, which will be available soon.

(5) Support tube R&D (H.Yamaoka, KEK)

(transparencies, 12 pages, pdf ,1.9MB ) He summarized the results of oscillation properties of two cantilevers (prototype) connecting with a thin plate. The cantilever is an aluminum plate of 100 (width) x 20 (thick) mm2 and the thin plate is 100 (width) x 2.5 (thick) mm2 , where the ratio of structural coefficients is 512. Two oscillation modes experimentally coincident very well with the thin plate. That is; frequencies were observed to be 26, 40, 161 and 187Hz as 1st, 2nd, 3rd, 4th mode, while they are calculated to be 30, 43, 184 and 197, respectively, by ANSYS. He also calculated several cases of different thicknesses of cantilevers (20 and 15mm, 20 and 19mm) and thin plates(0.5 ~ 2mm). Two cantilevers would start to oscillate with different frequencies for thinner "thin" plate. So, there must be optimized thickness for connecting two realistic cantilevers.

(6) IR/VTX simulation by Jupiter (T.Aso, Toyama National College of Maritime Technology)

(transparencies, 5 pages, pdf ,47KB ) He estimated background hits at the vertex detector (VTX) for various configurations of L*=2.3, 4.3 and 5m, where the thickness of the VTX-CCD is 330 micron-m. At the first layer, the background rates are 0.30, 0.35 and 0.40 hits/train/mm2 at L*=2.3, 4.3 and 5.0m, respectively. The results seems to be "unnatural" since we naively expect less hits at larger L*. He also showed distributions of the origins along the beam line. At the first layer, most of hits came from the IP, that is primary hits. In order to understand this "unnaturalness", he will analyze trajectories themselves and curling tracks.

The next meeting will be on 15 January (Wed.), 2003,10:00 - 12:00 pm at 3 gokan, 425 (in the process of scheduling, t) .