Minutes of 16th FFIR meeting on 10/4/2000

The meeting was held in a room of 3-425 at KEK, 13:30-14:40, 10/4/2000. We discussed on (1)prototype test (2) new mask system and (3) others.

(1) Prototype test (transparencies in Japanese, 12 pages of pdf ,925kB) Yamaoka reminded us the plan of support tube prototype test as already discussed at the previous meeting. Then, he showed some results of ANSYS calculations for the prototype. For the case of a single tube, the maximum deformations are expected to be 1mm at the first natural frequency of 24Hz with available acceleration force (max. 14cm/sec^2) and negligibly small at the second natural frequency of 30Hz. For the case of cantilever, they are calculated to be 0.9mm and 7 micro-m at the first(25Hz) and second(194Hz) natural frequencies, respectively. The calculations assume that the damping coefficient is 2% and the support is rigid.
In this week, the design of all components will be completed, then they are to be ordered to KEK machine-shop. The prototype system will be ready in this November. First test result will be available at the end of this year.
He expressed his strong interest in measurements of ground motions at B4 of Oho experimental hall where the prototype is going to be tested and KEK-site also. We discussed such possibility and we would like to ask N.Yamamoto-san how we proceed it.

(2) New mask system (transparencies,3 pages of pdf ,65kB) Sugimoto showed a new mask system for L*=4.3m corresponding to Pantaleo's new FF optics and B=3 Tesla. The L* is so far that the conical mask must not be needed. Luminosity monitor (or forward calorimeter) consists of two calorimeters located at about 2m and 4m from IP. The angular coverages are from 40mrad to 222mrad and from 20mrad to 40(+more)mrad, respectively. As we can see the third transparency, these calorimeters are outside of a core of e+e- pairs so that their performance must be as good as the conventional ones. He also looked at photons hitting in the CDC by JIM. He found that the number of photons was about half of the conventional design with L*=2m. He raised two possible issues, that is, (a) the performance of pair monitor may be worse and (b) compensating SC-solenoid may not be needed. Anyway, he will continue this study and he will present results at LCWS00.

(3) Others We discussed on the update of beam delivery system(BDS). Major issues are (a) extraction of momentum collimation section from the conventional collimation system(JLC Design Study) designed by Oide, whose primary purpose is a machine protection and the transverse collimation shall be located at a section from BC1 to pre-linac, assuming no beam-tail develops after the pre-linac collimation, and (b) the new FF optics with L*=4m. With 300m momentum collimation and 300mm FF, the total BDS length is about 600m. So, the another issue comes, that is, (c) how to prepare two IPs, for which big bend must be in front of the BDS. If the angular separation between 2 IPs is +/- 10mrad, the 2 IPs can be separated by about 10m, transversely, so they must be longitudinally separated by 20m at least. There must be large tunnel for the BDS and IPs . The FF optics is needed to estimate synchrotron radiation profiles for apertures of final quadrupole magnets. Muon protection must be investigated too.

The next meeting will be on 18 October (Wednesday), 2000 13:30 - 15:30 at 3 gokan, 425.