Minutes of the 3rd FFIR meeting on 1/27/2000

The meeting was held in a room of 3-425 at KEK for 13:30-15:30. We discussed on (1) 3 Tesla detector solenoid (iron structure), (2) support tube, and (4) extraction line.

(1) H.Yamaoka presented the 3 Tesla solenoid magnet design.(Transparencies, pdf, 2.11MB or tif, 15pages,2.19MB ) The major updates are (a) the shorter length of coil from 7.7m to 6.8m therefore the total length change from 14.4 to 13.5m and (b) one coil instead of 3 ones. First, the field distribution was calculated. The field uniformity became worse from1.4% to 4.6% since the current density of the coil was assumed to be uniform while it was adjusted in the previous 3 coils. The degradation can be recovered by changing the current density even for the single coil. Second, the magnetic force was also calculated. The longitudinal movement of the endcap was reduced from 4.8mm to 3.7mm. The single coil recalls an issue of support of the calorimeter since gaps between coils could be used for the support as mentioned in the JLC-1(Green Book). We ask Y.Fujii about this issue.

(2) H.Yamaoka presented the design of the tungsten masks with a rough idea of how to install them.(Transparencies, pdf, 2.11MB or tif, 15pages,2.19MB ) Since the total length of the iron structure is 13.5m, the support tube would be 16m long for the outside support positions. He thought that this length was too long for installation inside of the detector. So, he considered two separated tungsten masks without support tube, whose length is 7.7m each. The mask comprizes 4 pieces which are connected tightly by bands for barrels. The vertical displacement of the front was estimated to be 1.6mm for 40 tons (total weight), where support positions are 6.7 and 7.7m from the front. The 1st and 2nd eigen frequencies are estimated to be 17 and 91 Hz, respectively. For the smaller displacement and the higher 1st eigen frequency, supports must be necessary at the endcap (e.g. 4m from IP). Oscillation study is also highly needed.

(3)K.Kubo presented an optical design of dump line, up to a 2nd focus point (45m from IP) where the energy distribution and polarization of extracted beams can be measured. (Transparencies, pdf, 758KB or tif, 7pages,749KB ) Present assumptions are as follows. First magnet is located at 10.5m from IP. No magnetic field (such as solenoid and QC1 etc.) is considered in the 10.5m. Right after collisions at IP, the beam has normalized emittance (X/Y) of 1600/20 x10^{-8}m with beta_x/beta_y=4mm/0.15mm and alpha_x_alpha_y=1.5/0.0, which have been estimated by K.Yokoya. The beam is bent downward by two bending magnets, that is, 4cm below the beam line at the 2nd focus point. A 2cm dispersion (eta_y) is generated at the 2nd focus point, where the beam size was estimated as a function of energy (E'=E+dE or dE/E). The typical sizes are $\sigma_y=$1.7, 7.0 and 12 micron-m for dE/E=0, -0.005 and 0.01, respectively, while the beams are shifted vertically in 0, 100 and 200 micron-m because of the dispersion (eta_y=2cm). Therefore, we can measure the energy distribution with O(<0.1%) accuracy in principle. He also showed "survival ratio"s of disrupted beam as a function of energy with apertures of 8, 10 and 12 mm at the dump line. Only beam-particles of more than 70(80)% beam energy can survive with the aperture of 12 (8)mm. At the next meeting, he will estimate neutron yields as a function of distance from IP at the dump line for disrupted beams by CAIN, assuming 1 neutron is generated with 100 MeV (electromagnetic) energy deposit.

Next FFIR meeting will be held on 2/17 (Thus.) at 13:30-, 3-425, KEK, Japan. We will discuss on optimization on 3 tesla solenoid magnet , support tube/tungsten mask, super-QC1 and extraction line and others.