【作者】 邱琳；

【导师】 王小胡； 唐彬；

【作者基本信息】 西南科技大学 ， 物理学， 2021， 硕士

【摘要】 作为研究物质结构和动力学性质的理想探针,中子散射技术已在凝聚态物理、化学、生命科学、材料科学等领域应用。作为发展中国家拥有的第一台散裂中子源,中国散裂中子源(China Spallation Neutron Source,CSNS)于2018年11月顺利打靶并出束。CSNS一期建成的三台谱仪中,通用粉末衍射谱仪(General Purpose Power Diffractometer,GPPD)主探测器采用自主研发的大面积闪烁体探测器阵列,该探测器各项指标均满足谱仪要求。但该探测器存在探测效率均匀性较差、成本较高与制作工艺复杂等问题。硅光电倍增管(Silicon Photomultiplier Tube,SiPM)近年来发展迅速,具有比光电倍增管好的单光子分辨能力、易于集成、工作电压低、稳定性高、成本低廉等优点。本论文对基于SiPM阵列读出的闪烁体中子探测器进行研究,在GPPD主探测器的基础上,通过采用SiPM代替多阳极光电倍增管进行光读出来实现低成本、小死区、高探测效率均匀性等优异性能。SiPM闪烁体探测器主体结构采用双层闪烁屏夹芯结构,波移光纤垂直排布以实现二维位置分辨,后端光读出采用3 mm尺寸的SiPM。为实现探测器的工程应用,论文详细研究了核心元器件~6Li F/Zn S闪烁屏、波移光纤和SiPM的性能并开展了比对选型。对不同基材和厂家的闪烁屏,测试了其光产额以及中子探测效率等性能;测试了Y-11(200)与BCF-91A两种主流波移光纤的光衰减长度、光传输效率与弯折损耗;重点测试了光电转换元件SiPM的暗计数率、温漂、V-G曲线和耐辐照性能,并确定了用于探测器工程样机的SiPM型号、工作电压和封装规格。论文重点研究了基于SiPM阵列读出的闪烁体中子探测器的制作工艺,完成了一个有效面积196 mm×444 mm的闪烁体探测器工程样机的制作,并在中国散裂中子源的BL20中子束线开展了样机性能测试。测试结果表明探测器的避光良好,对波长为1.4?和2.8?的中子探测效率分别为32%与42%,利用插值法推算出探测器对2?中子探测效率为40.2%。利用狭缝对探测器的位置分辨能力进行测试,探测器像素大小为4 mm×4 mm,探测器的最高计数率为386 k Hz。同时,基于硅光电倍增管阵列读出的闪烁体中子探测器的效率不均匀性为35.81%,远低于GPPD旧版闪烁体中子探测器的67.73%。更多还原

【Abstract】 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%.更多还原