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"Linear Collider Gaseous Tracker R&D"

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After completed the R&D program on Jet chamber for JLC in 2003, the CDC group decided to move up to TPC R&D for ILC. This group has started a performance study of TPC since 2004, and simulation study byimplementing TPC into the full GEANT4 simulation frame work (JUPITOR) is also on going.

The TPC performance study has been carried out using the MPI TPC prototype, a Persistent-Current superconductive solenoid (PCMAG), and the Pi2 test beam from the KEK Proton Synchrotron (PS). Goals of this performance study are (A) to compare and understand the performance of different types of TPC such as MWPC, GEM and Micromegas, and (2) to demonstrate stable operations of these TPC in beam. This work has been carried out as an international collaboration with LC TPC R&D groups at MPI/Munich, DESY, Orsay and Saclay, and Carleton University.

The MPITPC is a small TPC prototype made at MPI/Munich. It has a detachable end-flange on which we mount a TPC end-detector of 10 cm x 10cm. The maximum drift distance is about 26cm. To readout out the TPC end-detector, we use the preamplifier and digitizer for ALEPH TPC. We can readout as much as 256 channels.

In the beam test, we make the best use of thin wall (20%rl) of the PCMAG. The inner diameter of the PCMAG is 850mm, the effective length 1m, and the maximum field 1.2T. The filed at the center is uniform enough for MPITPC although the magnet is an open magnet. For cosmic test, another PCMAG with yoke, and thus a better filed uniformity, is available at the KEK cryogenic center.

We have so far performed four beam tests at the pi2 test beam from KEK PS.:

(1) Test of a MWPC TPC in June 2004,

(2) Test of a TPC with three layers of GEM in April 2005,

(3) Test of a Micromegas TPC in June 2005, and

(4) Test of Micromegas (and GEM) with resistive anode readout in Oct 2005.

The MWPC TPC operated in the TDR gas in the test (2) was so called an メultimateモ MWPC having the anode wire spacing of 2mm and a 1mm gap between the anode wires and the cathode readout pads. The size of pads was 6mm x (6.3 mm x 2.3mm in pitch). Although the ultimate MWPC TPC provides an improved space resolution, it certainly suffers from the poor two-track separation and the large E x B effect. Although the group has been testing Japanese-made GEMs, in the test (2) we used the GEM foils from CERN. Here we employed a pad plane with 6mm x 1.17mm (6.3mm x 1.27mm) matching to a narrow signal of GEM. In the test (3) and test (4), we tested Micromegas TPC without and with the resistive anode. In both cases the pad size was same to one for MWPC. The test (4) was the first test of the resistive anode readout of Micromegas (and GEM) in the magnetic filed. In the test (4), the Carleton TPC prototype was also used.

We are getting understood our measured position resolutions and the pad responses, by a numerical calculation and a simulation, in term of pad pitch, diffusion, pad response function, and the effective number of primary electrons resulted from the fluctuation of gas amplification.

We are also working on newly produced GEM foils which are employing different methods (plasma etching and laser etching) for polyimido trimming by Japanese company.

Plans for the next year;

1) Complete small prototype test

2) Simulation study of TPC performance under realistic ILC condition

3) Optimization of MPGD-readout system (including digital TPC)

Plan for the next 2-3 years End-detector for a large prototype TPC under LC-TPC

We had submitted a budget request for large prototype TPC production for two years without any success. Our support is not sufficient to continue R&D program.