Development Of Scintillator Neutron Detector Based On SiPM Readout

Neutron scattering techniques are playing an important role in the study of material structure and dynamic properties,which are widely used in various subjects.As the first spallation neutron source in developing countries,China Spallation Neutron Source(CSNS)was successfully released the first neutron beam in November 2018.In the first phase of CSNS,three spectrometers have been built,the general powder diffraction spectrometer(GPPD)is one of them.The main detector of GPPD is large area scintillator neutron detector array(SNDA).The parameters of the SNDA have fulfilled the requirements of GPPD.However,the detector has some problems,such as poor uniformity of detection efficiency,high cost and complicated manufacturing process.Silicon photomultiplier(SiPM)is developing rapidly in recent years as the photoelectric detection device.It has better single photon resolution,and it is easy to integrate with small size,low power operation,good reliability and low cost.Therefore,the scintillator neutron detector based on SiPM array readout is studied in this paper.The scintillator detector based on SiPM readout system is the upgraded of the main detector of GPPD,SiPM is used to replace multi anode photomultiplier tube for light reading,this detector can realizes low cost,small dead zone,high detection efficiency uniformity and so on excellent properties.The scintillator neutron detector based on SiPM readout still consist of multi-scintillator screens sandwich with double-layer WLSF which is used to collect and to transmit the scintillator light.The 3mm size SiPMs are chosen as the optical readout device.In order to realize the engineering application,the performances of the core components ~6Li F/Zn S scintillators,wave-length shifting fiber and the SiPM were studied in detail.The light yield and neutron detection efficiency of ~6Li F/Zn S scintillators made of different substrates and manufacturers were tested.The optical attenuation length,optical transmission efficiency and bending loss of Y-11(200)and BCF-91A were tested.The dark count rate,temperature drift,V-G curve and radiation resistance of SiPM are tested.The SiPM model,working voltage and package specification are determined.The paper also focused on the new manufacturing technology of the detector with SiPM readout and a scintillator detector engineering prototype was developed with 196 mm x 444mm effective area.The performances of the detector prototype were obtained in the BL20neutron beam line in CSNS.The test results showed that the detector has good light avoidance and the efficiencies are 32%and 42%respectively when the neutron wavelength is 1.4?and2.8?.So,the detector efficiency is calculated as 40.2%for 2?neutron wavelength using the interpolation method.The position resolution of the detector prototype was tested by using a Cd slit.The position resolution is 4 mm×4 mm.The highest count rate of the detector prototype was 386 k Hz.At the same time,the inhomogeneity of the neutron detector efficiency based on the SiPMs readout is 35.81%,which is much lower than that of the previous version detector with MA-PMT readout as 67.73%.