Minutes of 37th FFIR meeting on 4/12/2002

The meeting was held in a room of 3-425 at KEK, 13:30-15:00, 4/12/2002. We had a TV conference with Niigata(Iwai), Toyama(Aso) and Tokyo(Aihara) universities. We discussed on simulation studies of beam delivery system based on GEANT4. After the TV conference, we discussed on distributions of disrupted beam at the dump line and a design of final focus superconducting magnet.

(1) TV conference

After a brief explanation of the JLC beam delivery system(BDS) by Tauchi, we discussed on a possible framework of simulation in this system. The BDS covers collimation, final focus systems, interaction region and dump(extraction) line, which is from the exit of main linac through the beam dump. Since our target is to estimate backgrounds in the JLC detector, GEANT4 was chosen as a common simulation program. Previous studies has used separate programs for backgrounds, i.e. muons by MUCARLO, synchrotron radiations by MQRAD, e+e- pairs, neutrons by GEANT3 and neutrons by FLUKA98, etc..

It was agreed that for such studies detailed geometries must be clearly specified and posted on a web-site ( probably, acfahep-ffir group site ). Parts of beam lines and detectors are desired to be "decoupled" in the GEANT4-framework as much as possible. It means that an interface between them must be well-designed so that NLC or TESLA beam lines can be easily implemented in the simulation for an example. Since NLC group has already started to simulate machine-related backgrounds by GEANT4, it is better to know their method and present status at the beginnng.

we agreed on further discussion on this study. A. Miyamoto will arrange the second TV conference, where an explanation of JUPITER (JLC detector simulation based on GEANT4), NLC study and work-sharing will be discussed.

(2) Particle distribution at quad by tracking-1 at the dump line (Kubo)

(transparencies, 2 pages, pdf ,86kB ) K.Kubo showed particle distributions at QC1, QF1, QD1 and BH1 of the dump line by SAD-tracking. The distributions is very asymmetric in horizontal direction since the disrupted beam has "low energy" tail and passes through a superconducting QC1. The present geometry assume a superconducting magnet with l*=4.3m for the final focus magnet as a current design.

(3) Design of superconducting magnet (Tsuchiya)

(transparencies, 2 pages, pdf ,154kB ) Instead of K.Tsuchiya, T.Tauchi showed a design of superconducting final focus magnet. It is QD0 with a field gradient of 64.35T/m and 3.35m long, which is equivalent with the QC1. The inner radius is 8cm. The super conducting coil is heat-insulated by three stainless steel pipes; which are 3mm-thick inner vacuum vessel, 8mm-thick 90K thermal shield and 6-mm thick inner He vessel, and it is tightly supported SUS collar. The outer radius is 27 cm. The other upstream magnets are conventional warm-iron ones, which will be designed by K. Egawa (accelerator). The design must be taken account of the particle distributions given by K.Kubo.

The next meeting will be on 25 April (Thu.), 2001 13:30 - 15:00 at 3 gokan, 325.