Minutes of 8th FFIR meeting on 4/21/2000

The meeting was held in a room of 3-525 at KEK , 13:30-14:30, 4/21/2000. We discussed on (1) Pantaleo's new FF optics, (2) dump line and so on.

(1) Pantaleo's new FF optics: transparencies(2 page of pdf, 15kB) N.Yamamoto briefly reported the present status of the new FF optics at KEK. First, he reviewed JLC optics ( so called Oide's optics ) which has two separate CCSs (Chromaticity Correction Sections) upstream of final doublets, that is, CCX(horizontal) and CCY(vertical). In each section, higher modes can be "automatically" canceled because of "pai" phase. The total length is ~600m. Second, new optics, so-called Pantaleo's optics, was explained. There is only one CCS where CCX and CCY are overlapped and a small CCS is inserted between final doublets(QC1 and QC2). So, this configuration is compact and the total length is 300m. Because of reducing CCS, the Pantaleo's optics has significantly less bending magnets. He noticed that K2-values are very different, that is, Oide's K2(SD)=-0.88 while Pantaleo's K2(SD)=330. K2 represents strength of sextupole. However, the pole field (B_pole) can be estimated by K2*a^2, where a is an aperture of the sextupole. If a=1cm, B_pole=330 *10^{-4}=0.03tesla (300Gauss) for Pantaleo's. So the sextupole is not so strong. There was a discussion on the strength of bending magnets; can the length be shorten with stronger magnetic field possibly provided by superconducting magnets? such ... Answer is "No" since the magnetic field strength is limited by radiations. He pointed out that Pantaleo's tuning knobs may be non-linear while Oide's ones are linear and independent of CCX,CCY-sections. We should aware of the tunability also. Presently he could not observe good cancellation of higher modes in Pantaleo's optics, so, he is in middle of debugging the new optics.

(2) Dump line: After the previous meeting, Kubo got a program from Miyamoto to calculate magnetic field along extracted beam line. transparencies(2 page of pdf, 21.3kB) However, the precision was not enough. Miyamoto is preparing updated routine with finer mesh sizes in his ANSYS calculations, which will be available in next week (4/23-).

(3) Sanuki (University of Tokyo) joined in our group since the previous meeting. He is going to estimate machine backgrounds from main linac through collimation/final focus sections. At the first step, he downloaded SAD program to his linux-computer. He succeeded to compile the SAD, but failed to execute an example program. Anyway he launched his new job for JLC. It is great!

(4) Others. In this year, we will upgrade our computing system for ANSYS-analysis and we will make a prototype of support tube to verify our calculations for ground motions.

The next meeting will be on 10 May, 2000 13:30 - 15:30 at 3 gokan, 425.