Minutes of 32nd FFIR meeting on 11/15/2001

The meeting was held in a room of 3-216 at KEK, 13:30-15:10, 11/15/2001.

First, we discussed on the new FF optics and superconducting final quadrupole magnet (SC1). The FF optics has not been optimized yet with L* >4.3 m. The present optics is still the Pantaleo-Frank one with L*=4.3m as follows;

----------------------------------------------------
Element  Length   distance    Field gradient@at Ebeam=250GeV
                 from IP (m)      (T/m)
QF1.1       2       16.52       22.4     QC2
QF1.2       2       14.53       22.4     QC2
D1          3.05    12.53
Dec.00      0.61     9.48
LX0.23      0.3      8.87
SD0.1       0.3      8.56                Sextupole(SD)
SD0.2       0.3      8.26                Sextupole(SD)
LX0.24      0.3      7.96
QD0.1       1.68     7.65      64.35     QC1
QD0.2       1.68     5.97      64.35     QC1
D0          4.3       4.3                 L*
IP          0         0
----------------------------------------------------
, where QD0.1,QD0.2 is QC1 and QF1.1,QF1.2 is QC2. The horizontal crossing angle is assumed to be 6 mrad. For an estimation of beam loss at the dump line, the aperture of SQC1 was set to be 9cm, which corresponds to the inner radius of SC1 vacuum vessel. The aperture of QC2 must be 1cm at least. K.Kubo will estimate the beam loss along the dump line in this case. He will also design the dump line up to a beam dump, where the beam shall be bent downward further.

Next, we discussed on sources of beam tail. Usually the tail can be generated by Coulomb scattering with residual gas molecules and wake fields at the main linac. The other sources are "daughter" bunches adjacent to nominal bunches, which may be generated at RF-gun, dumping ring and bunch compressors. Their energies may be higher than the nominal ones by 1%. If they pass through the IP without hitting beam pipe and magnets, there is no background problem. So, a band-width (momentum acceptance) shall be carefully studied at the final focus system. There are two kinds of band-width,i.e. for luminosity and background. Dark current is an another source at the main linac. Although most of them can not pass through the linac and absorbed at a momentum collimation right after the linac, they must be quantitatively estimated.

The next meeting will be on 6 December (Thu.), 2001 13:30 - 15:00 at 3 gokan, 425.