CASCA Chip-Based Readout Electronics System For The TPC Detector

TPC detector is a kind of high resolution track detector,which have been widely used in high-energy physics and astrophysics.Good readout system is a key step for the wide application of TPC detector.The nuclear electronics laboratory of Tsinghua University has developed the front-end readout ASIC(Application Specific Integrated Circuit)named CASCA(Charge Amplifier and Switched Capacitor Array)which is aimed to GEM-TPC detector.CASCA chip fulfils the function of pre-amplification,filtering,waveform sampling and serial output.Based CASCA chip,a modular,point to point readout system for TPC detector has been proposed in this article.And hardware,firmware and software have been developed.The hardware circuit of readout system is divided into three modules:Front-end card,Adapter card and Main-control card.Based on the full study of the electronics of casca chip,a matched control logic for sampling and readout,and digital conversion system was developed with an 8-channel output high-performance clock chip,low-power low-cost FPGA and lOMsps sampling rate,12bits precision analog-to-digital convertor.And for the higher data throughput needs in the future,the SRIO protocol is proposed to implement high-speed transmission between boards.Aiming at the control requirements of trigger mode selection,clock output and soft trigger in the readout system,a practical instruction control scheme is designed.The readout system can be controlled by the host computer.At the same time,the matching computer GUI monitoring software was developed to realize the waveform display of the sampled data and the instruction control of the readout system hardware.The idea of point to point has been adopted in the readout system.Several Adapter cards link to Main-control card with a HDMI cable.This system has compatibily for other similar readout ASIC by redesigning the adapter card.And a large number of Main-control cards in parallel could support thousands of channels in the large TPC detector.After testing,readout system work steady,the bandwidth of inter-board transmission based SRIO protocol is 2.014Gbps and the sampling INL(Integral Nonlinearity)of the one channel is less than 0.55%.