Design And Application Of Low Frequency Noise Measurement System For Semiconductor Radiation Detector

In recent years,semiconductor radiation detectors have been widely used in space particle detection,nuclear power industry,biological protection and other fields.As the primary element of radiation particle information acquisition,the detector needs to work in extreme environment such as high temperature,high pressure and strong radiation,so the study of its antiradiation ability and reliability are urgently needed.At the same time,it shows that the defects of semiconductor devices are closely related to their low frequency noise.To this end,this paper designed a detector measurement system to obtain its low-frequency noise,in order to provide proof to assess its anti-radiation ability and reliability.The analog part of this system is mainly composed of low-noise preamplifier,two stage amplify and DC offset circuit,adjustable cut-off frequency low-pass filter,single-ended to differential and 18-bit high precision ADC circuit.As the low-frequency current noise of semiconductor detector is very low,about pA Hz level,which is extremely easy to be annihilated by the inherent noise of the measurement circuit,so the design of system focuses on low noise preamplifier.It adopts the transimpedance amplifier structure,with three different feedback resistors,based on fA input bias current electrometer amplifier.The post-stage circuits,including anti-aliasing filtering and offset adjustment,makes further processing of the signal output from the preamplifier.At the same time,MSP430 F5529 microcontroller controls the circuit modules through the SPI,I2C protocol.Low-frequency noise data of the detectors that collected by system is transferred to PC via USB,which is used for spectral estimation and parameter analysis.After the system is designed and built,its performance is evaluated,including zero offset,temperature drift,and the noise power spectral density are also assessed under different ranges.Finally,this system measures the SiC neutron detector and demonstrates that the low-frequency noise of the irradiated detector is significantly increased compared to unirradiated one.The current noise power spectral density of former is about 1259pA~2/Hz,yet the latter is about 0.1pA~2/Hz at 1Hz.Meanwhile,the DC leakage current of irradiated detector is 189nA at 100V bias,three orders higher than unirradiated detector.The designed system can accurately measures the semiconductor detector weak DC leakage current and current noise and can be used for judging the performance degradation and reliability of the detector,which has certain practical value.