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Feasibility of measurements

At present the most promising detector is a pixel type such as CCD vertex detectors[7] in order to measure dense positions of particles. We do not need to measure their energies since momenta of our interesting particles are analyzed by the 2 tesla solenoidal magnetic field as described in the previous section. The densest regions are tex2html_wrap_inline1077 and tex2html_wrap_inline925, whose density is estimated to be 120(particles) x 72(bunches) /4.1cmtex2html_wrap_inline1443 (0.32MHz/cmtex2html_wrap_inline1443) if the detector can be read out only between RF pulses at 150Hz for the JLC-I[9]. The occupancy rate is below 1% in the CCD-detector with 25x25tex2html_wrap_inline1447mtex2html_wrap_inline1443 pixel size. Assuming that the energy of electrons(positrons) traversing the detector is 200MeV, the total dose is estimated to be 110Krad for a year(100days)'s experiment. This estimated dose is very close to present life time of CCD-detectors. For experiments in several years, we should need more radiation-hard CCD detectors resisting up to 1Mrad. Since there are good prospects, megarad hard CCD detectors are available in the near future[7, 8]. In order to get any useful information inside a bunch-train of 201.6nsec (2.8ns x 72bunches), it is greatly required to have a fast-gating CCD. Since there is few possibilities to realized such a CCD in future, it is very difficult to extract informations for each bunch during collisions. However, there is a solution to get information inside the bunch-train when one of two LINACs can be operated with a single bunch which is called a test beam. This test beam can probe inside the bunch-train in the other LINAC by colliding with the specific bunch in it at IP. We can easily choose any bunch to be probed in the train by adjusting a timing of the test beam. For this test beam operation, any information concerning a bunch property can be obtained.

As clearly seen in Tab.1, where measurement errors are statistical ones corresponding to numbers of bunch collisions listed in the second column, beam sizes (tex2html_wrap_inline741) and vertical displacements can be measured sufficiently even for a single bunch. For the measurements of transverse rotations a few bunch trains must be necessary for the statistical accuracy.


next up previous
Next: Conclusions Up: Nanometer Beam-Size Measurement during Previous: Measurement of transverse rotation

Toshiaki Tauchi
Sat Dec 21 00:34:16 JST 1996