Research Of A Large Area Detection Device Forβ-ray

Radioactive contaminationin nuclear sites cannot be ignored. With alpha raysshow their penetrating power very weak and cause the inconvenience when detecting.Gamma rays, you need to make the initial screen to do the shielding work. This papermainly studies a large area beta ray detection device, to match such as the type of largedoor for whole body beta contamination monitoringwhich needs the situation ofcombined probes.This task stems from “863plan” project “development of energy spectrumdetection instrument with high-precision”.Based on the retrieval and analysis of thebeta contamination instrument at home and abroad, refer to content achievement andrelated literature. And interaction theory ofthe rays toward matter combined withMonte Carlo method. As we know, beta rays interact with matter mainly with ionizingradiation loss and damage energy loss two ways, also have strong electron scatteringphenomenon. Monte Carlo method is widely used in nuclear physics experiments, forthe study provides a short cut to a certain extent, using MCNP5program to simulateelectronics, photons. It can also simultaneously simulate the resulting photons, andgives the lifelike image transport process, relatively, and descriptionof the detailedmathematical basis. With powerful geometry modeling, and the variance techniquesofparticle transportduring the process is more abundant. The use of plastic scintillator forβ detection has its unique advantages, but in this study, the plastic scintillation andphotomultiplier tube mismatch in geometric, need to be optical coupled, in order tomakethe photonsproducedincident to the photocathode of photomultiplier tube as moreas possible, this is the focus of the paper.First, Monte Carlo method is used to simulate thedetection efficiency ofplasticscintillation forβ rays and γrays, then carry out a large area β detection devicegeometric model building, take the standard source90Sr+90Ywhichreleases beta rays,itsmaximum energy is0.546MeV. After detection simulation, it is concluded that:(1) Using the Monte Carlo method forsimulationof the count results of low,medium and high energyβrays affectedby γ dose field, it is concluded that: using highβ/γ detection efficiency plastic scintillation slice when thickness becomes0.1cm, γ-raycounting onβ-ray interference effect can be neglected. (2) In exploring aluminum film to avoid light in, through the theoreticalcalculation ofrange of β-ray in aluminum, and refer to the actual production ofaluminum film thickness,determine the thickness of aluminum filmfor12microns, cansimultaneously satisfy theβparticle energy loss as little as possible (about18keVloss,energy responseof large gantry monitoring device:>100keV) and avoiding light in.(3) Using the Monte Carlo method simulation to optimize the device side slopeAngle, it is concluded that:intersection surface with photomultiplier tube Angle is70°,the adjacent two side Angle by50°, can meet the requirements of installation of thedevice on the door type monitor and the reflective effect is good.(4) About the simulation studyofβ-raytraverse aluminum film causes its energystraggling and angle deviation, it is found that the maximum energy0.546MeVof90Sr+90Y source appear0.8keV energy straggling,angle deviation of particle forcollimating beam within0-20°becomes apparent, but little impact on the detectionresults of the large area equipment.In the end, theproduction processof prototype was presentedas well as the outputpulse signal by the preamplifier circuit measurements. When the device prototypeproduction completed, using oscilloscope tomeasure the signal, it is concluded that: thepulse signal amplitude is controlled about600mv, sometimes the amplitude can reachmore than1V, rising time within100ns. It can well meet the requirements of thesubsequent processing circuit.