**(1) H.Yamaoka presented the support system for QC1 and tungsten mask.
**(Transparencies, pdf,
29 pages,6.85MB). As discussed in the previous meeting, he analyzed the support system
without the support tube. It consists of conical and cylindrical tungsten
masks, inside of which there are QC1 and QC2 magnets. There are two fixed points
at 7 and 8 m from IP in each. The total weight is estimated to be 81 ton for
both two systems. The gravitational sag is 1.6mm at the front and the maximum
stress is 23MPa. He executed three kinds of analyses, that is, Modal analysis,
harmonic oscillation (resonance response) and spectrum analysis, for two cases
of rigid and "soft"(15Hz spring constant) fixed points with ANSYS program. The
case of "soft" fixed points resembles might be realistic. From the Modal
analysis, the first, second and third eigen frequencies were calculated to be
17, 81 and 173Hz, respectively, for the rigid case. They become 15, 38 and
105Hz for the "soft" case. Responses were estimated at resonances by the
harmonic oscillation analysis. Inputs of oscillations are measured values at
Tsukuba-hall as previous analysis. With a typical damping ratio of 2%, the
maximum displacement was calculated to be 8.2nm on 15 Hz resonance at 2m from
IP. Relative displacement between two QC1's can be estimated by the spectrum
analysis for any kinds of ground motions. He is learning how to estimate it for
"un-correlated" ground motions (with any phase differences).
Since the gravitational sag seems to be large, he added one more fixed point at
3.85m from IP, where the tungsten mask can be supported on pole tip (iron
structure). The sag becomes much smaller value of 0.09mm with the maximum
stress of 5MPa. The first and second eigen frequencies increase 71 and 189 Hz,
respectively.

He also presented a method of assembling the tungsten mask which must be divided into 4 pieces. Basically the same talk will be given at the ISG5 meeting, SLAC, in next week.

**(2) Y.Sugimoto presented "Beam background hits in the JLC detector with
different mask configurations".**
(Transparencies, pdf, 6
pages, 154KB )
At B=3 Tesla, the size of the CDC shall be reduced to 2/3 for the same
geometrical acceptance as that at B=2 Tesla although the momentum resolution
gets slighter worse for the shorter lever arm. Therefore, the front face of the
endcap calorimeter can move at 1.9m from IP. Since the conical mask covers up to
2m from IP, thickness of the cylindrical mask which surrounds QC1 may get
thinner. He first calculated energy deposits due to photons and neutrons in the
calorimeter as a function of the thickness. He found a steep and shallow
deceases for photons and neutrons, respectively. Without the mask, the energy
deposits were 7.5GeV(photons) and 4.4GeV(neutrons) per bunch crossing. With 2cm
thickness, they becomes about 1/5 and 70%. The CDC hit rates were also
calculated. The results are more impressive, that is, all the hit rates were
"negligibly" small. This tells us that the calorimeter works well even for no
mask case. Then, he presented an aggressive mask configuration. The major
change is the conical part. The angular coverage is from 60 to 100mrad and the
top is located at 1m from IP. Even with this configuration, backgrounds was
estimated to be small.

**(3) K.Kubo updated the "JLC dump line design" to reduce beam loss.**
(Transparencies, pdf, 4
pages, 530KB or tif, 4
pages,523KB
)
The major change was to move the vertical bend further near the second IP. He
showed the energy distributions of loss particles for various apertures. He
also showed neutron yields ,which can be directly seen from IP, as a function of
aperture. The realistic aperture produced neutrons with a flux of
10^{15}/cm^2/year. It exceeds the tolerable flux by 10^5 times.

**(4) K.Kubo presented "Beam tail study in main linac tracking", since the most
difficult one in the pre-linac collimation is a longitudinal collimation of beam
tail.**
(Transparencies, pdf, 4 pages,
447KB or tif, 4 pages,441KB
)
He found that 5 sigma_z collimation is necessary for momentum range of +/- 2%
after the main linac acceleration.

**Next FFIR meeting will be held on 3/8 (Wed.) at 13:30-, 3-425, KEK,
Japan.** We will discuss on 3 tesla solenoid magnet , support
tube/tungsten mask, super-QC1 and extraction line and others.