Monte Carlo Simulation Study Of Timing Performance Of SiPM-based Plastic Scintillator Detector

Time-of-flight detectors(TOF)are an important part of high-energy physics experiments.In collider experiments,some particles(π,K,P,etc.)need to be determined by measuring their flight times.And the ability to distinguish these particles depends on the detection accuracy of TOF.Therefore,it is very necessary to understand and study the performance of TOF in terms of time performance,in order to explore the factors that affect its performance,so as to improve its detection ability.In this paper,we choose a plastic scintillator detector based on silicon photomultiplier(Si PM)as TOF for research.In the past,people often used photomultiplier tubes(PMT)as photon detectors on TOF,but due to its sensitivity to magnetic fields,large size,and high operating voltage,it is not suitable for applications in strong magnetic field environments and integrated systems.Therefore,we choose Si PM,a new type of semiconductor detector,as the photon detector in the TOF system.Si PM has the characteristics of high gain,insensitivity to the magnetic field,excellent photon detection efficiency(PDE)and time resolution.Because of its superior performance,it has attracted more and more attention from scientific researchers this year.Plastic scintillator is a kind of organic scintillator,which has the characteristics of fast time response,simple production,low price and good luminescent performance.Due to the excellent performance of both Si PM and plastic scintillators,in many large-scale experiments such as LHCb and BSEⅢ experiments,the combination of the two is proposed or has been applied.In order to explore the factors affecting the time performance of the detector,and to provide guidance for the subsequent construction of a scintillator detector with high time resolution.This paper mainly carried out the following three aspects of work.The first aspect is to construct the optical response model of the plastic scintillator detector based on Si PM,and carry out more detailed research on the detector through the method of simulation,so as to provide data and theoretical support for the construction of the actual detector.The second aspect is to build a test platform based on Hamamatsu S13360-2050 VE MPPC.While testing Si PM characteristic parameters,it can verify the optical response model through experiments and provide data support for subsequent TOF performance analysis.The third aspect is based on the high-energy Kedi HND-S2 plastic scintillator,Saint-Gobain BC-408 plastic scintillator and Hamamatsu S13360-2050 VE MPPC through the optical response model to initially analyze the factors affecting time resolution.The optical response model of the plastic scintillator detector based on Si PM is mainly divided into two parts: plastic scintillator and Si PM.The Geant4 software is mainly used to establish the geometric entity of Si PM and the plastic scintillator response model.After the plastic scintillation geometric entity is established,it is filled with the parameters required for normal work,such as light yield,refractive index,decay time,etc.After that,a digital Si PM response model is established,and the influence of Si PM dark count,after-pulse,optical crosstalk and other characteristics as well as the nonlinearity of Si PM under high light intensity are considered in detail in the model.After the Si PM response model is established,the modeling of the entire detector system is preliminarily completed.Finally,using the optical response model,the influence of Si PM and plastic flash characteristics on the time resolution ability of the detector is preliminarily studied by the method of controlling variables.In terms of experimental testing,the test platform we built mainly measures the gain and photon detection efficiency(PDE)of silicon photomultipliers,both of which are important characteristics for understanding the performance of Si PM applications under low or even extremely low light conditions.In this work,we set up a series of experimental devices and determined the corresponding testing procedures.Using a fixed-wavelength light source at 405 nm,we quantified the gain and PDE of the Si PM at different temperatures and bias voltages.In order to ensure that the Si PM works under low or even extremely low light conditions,two integrating spheres were set up in the experiment,and they were linked together with a lighttight device.We present the breakdown voltage,gain,and PDE measurement methods and results for the Hamamatsu S13360-2050 VE MPPC.In addition,at 25°C,we obtained results consistent with the data given by the manufacturer.The temperature and bias voltage dependence of Si PMs can provide guidance for their use,such as gain compensation of readout circuits,optical modeling of Si PMs,and optimization of operating conditions for Si PM-based detectors.Based on the three aspects of scintillator structure and reflective layer material,scintillator and Si PM time characteristics,and Si PM characteristics at different temperatures,based on high-energy Kedi HND-S2 plastic scintillator,Saint-Gobain BC-408 plastic scintillator and Hamamatsu S13360-2050 VE MPPC conducts a preliminary analysis of factors affecting time resolution.In the analysis of the scintillator structure and reflective layer materials,we found that increasing the size of the scintillator and using materials with high reflectivity as the reflective layer will make the time resolution of the detector worse.However,the opposite result was obtained under the condition that the increasing direction of the scintillator size coincided with the incident direction of the charged particles.Through the analysis of the time characteristics of the scintillator and Si PM,we found that even if the Si PM has a faster rise time,the closer the rise time of the Si PM and the rise time of the scintillator is,the better the time resolution is.Based on the analysis of the time-resolved effect of Si PM properties at different temperatures,we found that lower temperatures give better results.And while analyzing the three aspects,we have described the reasons behind these results and given corresponding suggestions for the results obtained from the analysis of different aspects.