Design Of Readout Circuit For Particle Detector

As Micro-structure gas detector has advantages of high time accuracy and spatial resolution,good radiation resistance,high gain and can be made as large scale detector,it has developed rapidly in recent years.Micro-structure gas detector also has been μsed in many fields like High-energy physics experiments,nuclear medicine imaging,safety monitoring,and space astronomy,etc,because of these advantages.However,compared with the fast development of gas detector,the research of readout circuit is relatively slow.Therefore,it is significant for design of readout circuit system which used for gas detector.The readout circuit system is capable to detect some unknown particle signal which collected by the fronted particle detector,and measuring the energy characteristic and flying time information of the unknown passing particle.According to the data acquiring from the readout circuit system,can furtherly determine the type and physical properties of unknown particles.In this paper,principle about the readout circuit system acquiring the energy and time information of the unknown particle is firstly introduced.According to the development status of readout electronics at home and abroad,the readout system in this paper is designed by comparing representatives of readout electronics home and aboard like Medipix,Timepix and GOSSIPO,etc.The fronted circuit of readout system include preamplifier,voltage discriminator,10-bit SAR ADC,oscillator,logical control circuit and 3 shift registers as 4-bit,12-bit and 10-bit,respectively.The feedback capacitance is used to collect the charges which produced in the detector by passing particle in the fronted circuit.The charges in capacitance is discharged by MOS switch.After converting the charges into voltage signal proportional to quantity of electric charge,the signal is divided into 2 ways.One is used to measure time information,the other one is used to measure energy information.The time information measurement is dependent on Time-Digital Convertor(TDC),TDC circuit consists of voltage discriminator,oscillator and 2 counter as 4-bit and 12-bit respectively.The energy information measurement is completed by the Analog-Digital Convertor.The all readout circuit system is composed of 4×4 pixel array.The unknown particle information is binarized and shifted out through the shift register in pixel unit.The readout circuit of particle detector designed in this paper uses TSMC 180 nm CMOS process.And it occupies 1110μm×1325μm(weight×height,4×4 pixel array total dimension,include ESD,PAD).The chip works with 1.8V power supply,The time resolution of Time-of-Flight is 1ns,and the dynamic range of unknown particle which can be detected is 1fC~150fC.The range of Time-of-Flight is about 40μs.