Development of the time projection chamber with micro pixel electrodes

1. Development of the time projection chamber with micro pixel electrodes H. Kuboa, K. Miuchia, T. Nagayoshia, A. Ochib, R. Oritoa, A. Takadaa, T. Tanimoria, M. Uenoa aDepartment of Physics, Kyoto University, Japan bDepartment of Physics, Kobe University, Japan AbstractThe TPC based on the gaseous chamber with micro pixel electrodes (m-PIC) has been developed for measuring three-dimensional tracks of charged particles. Anode pixels are formed with 0.4 mm pitch on the strip aligned perpendicular to the cathode strips in order to obtain a two-dimensional position. In the TPC with area of 10 cm square and drift length of 8cm, a uniform electric field of about 0.4 kV/cm is produced. For encoding of the three-dimensional position a synchronous readout system has been developed using FPGAs with 40 MHz clock. The TPC with the system enables us to reconstruct the three-dimensional track of the particle at successive points like a cloud chamber. The drift velocity of electrons in the TPC was measured with cosmic muons for three days, during which the TPC worked stably with the gas gain of 3000. Furthermore a three-dimensional track of a Compton scattered electron was taken successfully 1. Introduction To solve the problem In 2001 we developed Micro Pixel Chamber (m-PIC) [1] classified as a micro-pattern detector as signal electrodes with gas amplification In 2002 we developed a TPC based on the m-PIC. Problem of traditional TPCs A part of ions produced in the avalanche around the sense wire accumulate in the drift volume and distort the electric field Space charge increases in the avalanche region. 2. Detector Design m-PIC Field cage Electric field calculated by Garfield[4] around anode electrodes the avalanche multiplication due to a strong electric field higher gas gain than MSGC without discharges [1, 2]. two-dimensional readout 10cm x 10cm m-PIC was developed [1, 3]. Readout electronics system FPGA 40MHz Xilinx Virtex-E 30 cm t=16ns ATLAS TGC ASD 10 cm Signal shape of cathodes for one incident cosmic muon 3. Performance Three-dimensional track of a Compton-scattered electron (solid line) and its projection on the planes (dot lines), when 511 keV gamma-ray is irradiated. Kr(90%):ethane(10%) Drift velocity Application to the gamma-ray imaging is reported in Ref. [6] Two-dimensional imagetaken with m-PIC. In the drift region b-decay electrons were emitted from 85Kr. Ar(80%):ethane(20%) References [1] A. Ochi, et al., Nucl. Instr. and Meth. A 471 (2001) 264. [2] T. Tanimori, et al., Nucl. Instr. and Meth. A 381 (1996) 280. [3] T. Nagayoshi, et al., in this conference [4] R. Veenhof, Nucl. Instr. And Meth. A 419 (1998) 726. [5] U. Becker, et al., Nucl. Instr. and Meth. A 421 (1999) 54 [6] R. Orito, et al., in this conference (circle)this work (dot line)Ref.[5]