The TOPAZ Time Projection Chamber

Abstract A Time Projection Chamber (TPC) is under construction for the TOPAZ e + e − experiment at TRISTAN. The dimension of the TPC is 260 cm in diameter and 300 cm in axial length. Fin-type fine field cages are set inside GFRP insulator cylinders which also serve as the pressure container. The sector is made of multilayer G10 boards for better electric and thermal isolation. The cathode pads are substantially larger in area than those of the PEP4-TPC and having zigzag-shaped boundary. These serve to maintain high spatial resolution with fewer number of pad channels. Signals are amplified by low noise preamplifiers and shaping amplifiers, and, stored and digitized by FASTBUS based CCD-digitizers. Digitized information is preprocessed and sent to VAX 11/780 at a rate 2 MHz per 32 bit word. Nitrogen LASER beam will be used extensively with the LASER beacon system for calibration. Test results on production prototypes are also reported.