Minutes of 23nd FFIR meeting on 2/28/2001

The meeting was held in a room of 3-425 at KEK, 13:30-14:30, 2/28/2001. We discussed on a neutron background estimations, present status of studies and the ACFA report.

(1) Neutron background estimations A. Miyamoto reviewed the neutron background estimations in order to verify numbers in the draft. The most updated numbers have been presented at the LC99 in October,1999 by him. However, numbers in the draft are those which have been presented at LCWS99, May,1999 by Y.Sugimoto and some of them were wrong. Correcting the latter numbers, there are still differences as follows. The former is based on calculations by Fluka98, while the latter is based on GEANT-3. The numbers are all at the VTX first layer (r=2.4cm), and they are estimated for both beams.

sources     LCWS99 (GEANT3)    LC99 (Fluka99)
pairs       66 n/BX            252 n/BX
            3x10^7n/cm^2/y     14x10^7n/cm^2/y
BS photons  2x10^7/cm^2/y      5x10^7/cm^2/y
            6x10^20n/y generated in total
            1x10^17n/y back from water dump, which is located at 300m from IP.

We also discussed on a further study on the dump line. In the present draft, future improvements were mentioned on the self-shielding effect and additional shield. At present, we can estimate the back-scattering rate of neutrons from magnets by looking at the same rate at QC1 for e+e- pairs. The beam loss positions must be very useful to see possible locations of the additional shields along the beam line. We would like to include these improvements in the report.

(2) Present status N.Yamamoto identified a problem in the file of new FF optics. In matrix elements for the second order cancellation, an element of (1,2)-component was found to be non-zero which must be zero for the cancellation. He though that this problem creates higher order (3rd) aberrations increasing beam sizes at IP. He will try for the component to be zero.

(3) Discussion: ACFA report All sections except for the pair monitor have been received and they are posted on the web site of http://acfahep.kek.jp/subg/ir/group.only/acfarep/ . Next step is to edit them for consistent contents.

The next meeting will be on 14 March (Wed.), 2001 13:30 - 15:00 at 3 gokan, 425.