Tauchi explained the importance of a single-bunch operation of LINAC for beam diagnosis at IP. At present the beam profile monitor, such as CCD (pixel detectors), cannot provide an information of each bunch in a bunch-train because of its very short time-separation(1.4 - 5.6 nsec). When one of LINACs accelerate only a single bunch, we can use this bunch as a probe to look inside a bunch-train structure. In order to chose a specific bunch, a master timing of the single-bunch should be simply changed. It was pointed out by K.Oide that the single bunch operation may be necessary also during usual collisions since a condition of machines can be changed, which requires that there should be a single bunch in a bunch-train at 150Hz. There will be no problem for such operation. It was also emphasized by T.Matsui that a R/D of gating CCD should be pursued in parallel. This idea will be presented at LC95.
2) Present status of muon-backgrounds and a comment of muon source for a m+m- collider by Y.Namito
Namito summarized the two programs( MU_CARLO and MUON89) to calculate a generation and transportation of muons. The MU_CARLO is a Monte Carlo program which can take account of detailed geometry of FF-system while the MUON89 is an analytic calculation with no geometry. The former will be used for further calculations and it is filed in jlcux1:/home/namito/muatn where the documentation will be made by him. Then he showed the previous results, that is, the muon-attenuator with no magnetic field was more effective than that with 10KG because of the muon-reflection at the inner wall, and it reduced the muon-background down to one muon per 10^10 electrons if muons were created at 6000feet from IP. For LC95 he will calculate the background with a different material of the attenuator such as lead instead of iron because of its compactness. He will also calculate mu-production by polarized high energy photons of 250GeV for a possible muon-source of m+m- collider. It is expected that the emittance is roughly 1micron x 1mrad for such muons which is very close to the required one. The main point is that how many muons can be created.
3) Overview of a m+m- collider by K.Yokoya
Yokoya showed parameters and a scheme of 4TeV and 0.4TeV m+m- colliders which have been presented at the 2nd m+m- collider workshop, 1994 Nov. . The 4TeV collider; muons are produced by 30GeV PS with 2x3x10^13 protons/pulse at f_o=10Hz. The intensity of muons(N_mu) is 1.5x10^12/bunch = 0.15(mu/p) x 0.33(mu-survival) x 3x10^13, where the values of mu/p and mu-survival were given by B.Palmer. There may be Palmer's factors in them and the other places anyway, while the pessimistic mu/p is 0.03 etc. . The beam size(sigma) is 2.1micron at IP with 1.5 x 10^-9 m-rad emittance. The storage turn(n_s) is 1800 for B_ave=6Tesla, which is independent on the energy. The luminosity is calculated by f_o n_s N_mu^2 / 4pi sigma^2 = 3 x 10^34 cm^-2 s^-1 with a single bunch. The cooling is done by "ionization" through Li of 1.2km after the decay channel of 1.3km. Employing two small storage/accelerating rings which comprise super-Linacs with different frequencies, the mu-beams are finally accelerated up to 2TeV/beam in a main ring comprising TESLA-type LINACs(25MeV/m). This complex of machines is well fit at FNAL site. For muon-source the other ideas has been examined at the previous workshop, where none of them competed the above one. For an example, luminosity is less than 10^28 for electro-production by 50GeV beam(SLC).
We would like to consider a photo-production of muons by JLC-I (Ebeam= 250GeV). High energy photons are created by a famous Compton-backward scattering, which may be polarized to enhance a peak of muon-energies at close to 1/2 E(photon). So we may obtain high energy muons with reasonably low emittance because of the typical scattering angles of muons = mass(mu)/Energy(mu). There was another idea by T.Matsui. The main LINAC of JLC-I can be converted to the muon collider with the "conventional" muon source of 30GeV-PS. The point is that how a long bunched beam can be accelerate by JLC. The idea may be a multi-bunching of such beam. Anyway, we will continue this discussion.
4) Others
We discussed on a R/D of a support tube for QC1, mask and VTX etc. . This R/D is very important in order to ensure nano-meter beam colisions at IP. Up to LC93, Kanda(Hawaii univ.) had been working on it. He calculated ocscillation properties of the tube with measured ground motions, however it seems that he can not continue his work. No one proceeds his work since then. The next step must be a prototype test by making a "real" tube. We agreed to have a meeting for such a R/D. T.Matsui will organize the meeting soon with Kanda. Needless to say, this R/D is an essential subject for our conceptual design.