新型太阳中微子闪烁探测器的研制

概述了一种新型太阳中微子闪烁探测器的研制,其中载钆(Gd)液体闪烁体的Gd浓度达到5%、光的衰减长度≥150cm、对60keV的Gamma-ray之能量分辨率为21%(σ);直径1cm、厚3cm的GSO:Ce晶体,其发光产额约为NaI(Tl)晶体的20%、光的衰减时间为60ns、对662keVGamma-ray之能量分辨率为9.2%(σ).文章讨论了由这两种闪烁体构成的复合探测器的特点及作为太阳中微子探测器其本底的降低措施.对直径10cm、厚50cm的这种复合探测器的模拟计算表明其光的收集效率可达20%.     

塑料闪烁体β射线望远镜的能量刻度

建立了一台塑料闪烁体β射线望远镜并进行了能量刻度.利用一组端点能量从0.7MeV到6.1MeV的β~+发射体作为参考源,线性能量刻度的误差仅35keV.     

塑料闪烁体β射线望远镜的能量刻度

建立了一台塑料闪烁体β射线望远镜并进行了能量刻度.利用一组端点能量从0.7MeV到6.1MeV的β^±发射体作为参考源,线性能量刻度的误差仅35keV.     

ST401塑料闪烁体的脉冲中子相对光产额评估方法

介绍了脉冲中子在ST401塑料闪烁体上的相对光产额评估方法.采用Geant4蒙特卡罗软件模拟X射线和中子在闪烁体中的输运行为,记录产生的全部带电粒子类型和能量,由公式计算得到相对光产额.给出了不同能量的单个中子和单个X射线入射到1 mm,3 mm,5 mm,1 cm,2 cm,3 cm,5 cm厚ST401的平均相对光产额.在0.3 MeV脉冲X射线源和14 MeV脉冲中子源上开展验证实验,采用相同的图像测量系统记录相对光产额,给出了单个中子与X射线的平均相对光产额比值.模拟结果与实验结果相对误差小于10%.结果可以为宽能谱脉冲中子束图像测量系统的量程安排提供依据.     

重离子物理实验中的塑料闪烁探测器

前言塑料闪烁体的光衰减时间短,有较高的光产额,允许以高计数率探测粒子,在制作工艺上很容易加工成不同的形状和体积,并且成本低廉。由于以上一系列特性,使它在各种闪烁体中具有突出的地位,因此广泛应用于高能物理和核物理。     

塑料闪烁体中子探测效率及相对发光产额的标定

利用加速器中子源研究了用于标定塑料闪烁体中子探测效率及相对发光产额的实验技术 ,在四川大学原子核科学技术研究所 2 .5MeV静电加速器上 ,利用T(p,n)和D(d ,n)核反应作为中子源 ,在 0 .6—5MeV中子能区对直径为 40mm ,厚度为 5mm的 1 42 1塑料闪烁体的中子探测效率及相对发光产额进行了测定.A method used for the calibration of neutron efficiency and the relative photo yield of plastic scintillator is studied. T(p,n) and D(d,n) reactions are used as neutron resources. The neutron efficiencies and the relative photo yields of plastic scintillators 1421 (40 mm in diameter and 5 mm in thickness) are determined in the neutron energy range of 0.655—5 MeV.     

微量MgO掺杂对GAGG∶Ce晶体光学和闪烁性能的影响

共掺杂离子是优化晶体闪烁性能的重要手段之一,本文采用提拉法生长了GAGG∶Ce和GAGG∶Ce,0.1%Mg晶体。通过测试硬度、透过率、X射线激发发射(XEL)谱和符合时间分辨率等方法研究了微量MgO掺杂对GAGG∶Ce光学及闪烁性能的影响。GAGG∶Ce和GAGG∶Ce,Mg的维氏硬度平均值分别为1 430 kg/mm~2和1 420.4 kg/mm~2,表明Mg~(2+)的掺杂几乎没有对GAGG∶Ce的硬度产生影响。XEL谱结果表明,共掺杂Mg~(2+)后GAGG∶Ce晶体的发光峰值波长约为540 nm,但5d_1→~2F_(5/2)及5d_1→~2F_(7/2)发射峰红移了12～24 nm,Mg~(2+)的引入可能改变了Ce~(3+)的5d_1激发态向~2F_(5/2)和~2F_(7/2)跃迁几率分布。通过共掺杂Mg~(2+),发现尽管光产额由5.8×10~8 lx/MeV(58 000 ph/MeV)降低为4.15×10~8 lx/MeV(41 500 ph/MeV),但GAGG∶Ce,Mg符合时间分辨率得到了显著改善,达146 ps。此外,比较不同尺寸样品的光产额,发现GAGG∶Ce,Mg对闪烁发光的自吸收程度小于GAGG∶Ce。以上结果表明,微量MgO掺杂是优化GAGG∶Ce晶体闪烁性能的有效途径。     

液体闪烁体探测器测量皮秒激光脉冲中子源能谱

在星光Ⅲ实验装置上开展皮秒激光脉冲中子源实验,使用液体闪烁体探测器测得较好的中子信号,利用飞行时间法获得中子的能量/时间分布,通过示波器电压时间积分与阻抗之比得到不同能量段的电荷值。建立液体闪烁体探测器Geant4计算模型,通过实际打靶情况与标定情况下液体闪烁体探测器出光口收集到的可见光光子数之比,结合标定的灵敏度数据,获得液体闪烁体探测器对不同能量中子的灵敏度。计算得到源发射的中子能谱,能量在1 MeV以上的液体闪烁体探测器方向测得的中子产额为1.04108 sr-1。     

基于塑料闪烁光纤阵列的γ射线位置灵敏探测器数值模拟

基于蒙特卡罗的模拟方法,设计了一个基于塑料闪烁光纤阵列的γ射线位置灵敏探测器并对其性能进行了系统的研究。分析了该探测器在高能γ粒子辐照下的康普顿散射特性和圆形塑料闪烁光纤的能量泄漏情况,发现随着入射能量的不同,康普顿边缘峰值也相应变化,并且和入射光子能量一一对应。考虑阵列间粒子串扰的情况下,利用此特性得到该位置灵敏探测器在0.8~7.0 MeV的γ入射能量下,能量分辨率和空间分辨率分别能够达到10%和cm量级。但由于闪烁光纤原子序数较低,在较高能区的探测效率也较低,只有15%左右或更低。这就使得利用闪烁光纤阵列探测器不能同时满足较好的空间分辨率和能量分辨率,两者出现一定的矛盾。     

狭长CsI(Tl)闪烁体发光效率的研究

提出了基于狭长CsI（Tl）闪烁体和面阵CCD器件，采用光纤和光纤面板进行光耦合及传输，以扇形束线阵扫描方式实现对X射线探测与成像的工业X-CT系统探测器方案.基此，通过物理分析及数学建模，利用Matlab模拟研究了X光能量小于450 keV时狭长CsI（Tl）闪烁体的发光效率等性能指标.研究结果表明：当光电吸收截面μph和康普顿吸收截面μc分别为0.000313和0.0000295、反射层反射系数R和衬底反射系数Rs分别取0.95和0.8、荧光线性吸收系数σ取0.000222 μm－1时，得到狭长CsI(Tl)闪烁晶体的长度l、高度h和宽度w取值范围分别是926～4512 μm、242～5000 μm和242～5000 μm的结论.在此范围内，既可使闪烁晶体有较好的空间分辨率又可获得最高的发光效率.     

Scintillation properties of K2LaCl5 with Ce doping

In this work we present the scintillation properties of K₂LaCl₅ doped with Ce³⁺ concentrations of 0, 0.1, 1 and 10%. Under X-ray excitation the crystals show the efficient Ce³⁺ (5d–4f) luminescence between 340 and 400 nm. Depending on the Ce concentration, the light yields vary between 24,000 and 50,000 photons/MeV (ph/MeV). Experiments with 662 KeV gamma ray excitation show light yields varying between 13,000 and 30,000 ph/MeV. For Ce luminescence a single exponential decay time of approximately 40 ns is expected. However, for K₂LaCl₅:10%Ce, the decay is not single exponential. As a function of the time t, it can be described by a 1/t^1.63 behaviour for large t. With a crystal of K₂LaCl₅:10%Ce we obtained an energy resolution of 5.1% for 662 KeV gamma ray excitation of ¹³⁷Cs.     

An experimental study of the relative response of plastic scintillators to photons and beta particles

A scintillation counting system has been constructed with the use of BC-400 and EJ-212 series plastic scintillators along with a subminiature photomultiplier tube to investigate the effect of increasing plastic scintillator thickness on system-integrated counts. Measurements have been carried out using four different gamma sources with different energies ranging from 6 keV to 1.332 MeV and a Ni-63 beta source with a maximum energy of 66 keV. Scintillator thicknesses ranged from 10 μm to 2500 μm. The response of the system was determined by measuring the integrated counts as a function of scintillator thickness. These experimental findings were used to empirically determine the optimum thickness of scintillator material with which to build a low energy beta detector which discriminates against high energy gamma photons in a mixed radiation field environment.     

Growth and Study of Scintillation Properties of Orthovanadate Crystals Ca:GdVO<Subscript>4</Subscript> and Ca:YVO<Subscript>4</Subscript>

New scintillation orthovanadate crystals Ca:GdVO₄ and Ca:YVO₄ featuring intrinsic luminescence are grown. The spectra of pulsed cathodoluminescence of new scintillators and their luminescence decay time are studied. Using γ-rays with an energy of 662 keV from the ¹³⁷Cs source, total absorption spectra (so-called photopeaks) for new orthovanadate crystals are measured. It is shown that the light yield of Ca:YVO₄ and Ca:GdVO₄ crystals is 28100 photon/MeV and 14000 photon/MeV, respectively.     

Luminescence and scintillation properties of advanced Lu3Al5O12:Pr3+ single crystal scintillators

In this paper we present the luminescence and scintillation properties of Lu₃Al₅O₁₂:Pr (LuAG:Pr) single crystals with Pr³⁺ concentration of 0.13 wt %, grown by the Czochralski method. The light yield and energy resolution were measured under 662 keV γ-ray excitation. The dominant emission band peaking at 310 nm with a shoulder at 370 nm was observed in the photoluminescence spectrum. High light yield of 24,500 ph/MeV and an energy resolution of 5.3 % were obtained for a 6 × 6 × 2 mm³ LuAG:Pr sample. Light yield dependence on sample height and shaping time was measured. The estimated photofraction in pulse height spectrum and total mass attenuation coefficient at 662 keV γ-rays were also determined and compared with the theoretical ones calculated using the WinXCom program.     

Die Lichtausbeute des Plastikszintillators NE 102A für Elektronen von 3 bis 11 keV

The light yield of the plastic scintillator NE 102A for electrons has been measured as a function of electron energy between 3 and 11 keV and scintillator thickness between 0,1 and 50 mm. The scintillation response is a linear function of the electron energy down to energies of 4 to 8 keV, these values depending on the scintillator thickness. The light yield of thin scintillation sheets for low energies was observed to be considerately larger than for thicker sheets. Two possible explanations are discussed.     

Luminescence and scintillation properties of Lu0.8Gd1.2SiO5:Ce and Lu1.8Gd0.2SiO5:Ce single crystals: A comparative study

The luminescence and scintillation properties of Lu_0.8Gd_1.2SiO₅:Ce and Lu_1.8Gd_0.2SiO₅:Ce single crystals are compared. At 662 keV γ-rays, light yield (LY) value of 29,800 ph/MeV obtained for Lu_1.8Gd_0.2SiO₅:Ce is much higher than that of 20,200 ph/MeV obtained for Lu_0.8Gd_1.2SiO₅:Ce. The energy resolution of 6.0% obtained for Lu_0.8Gd_1.2SiO₅:Ce is better than that of 7.7% for Lu_1.8Gd_0.2SiO₅:Ce due to its better intrinsic resolution and proportionality of LY. The LY and energy resolution for α-rays, as well as a LY ratio under excitation with α- and γ-rays (α/γ ratio) are also determined. The intrinsic LY and light loss coefficient under excitation with α- and γ-rays are evaluated. The photofraction at 662 keV γ-rays is also determined and discussed.     

Luminescence and Scintillation Characterization of Cs2NaGdBr6: Ce3+ Single Crystal

Luminescence and scintillation properties of newly discovered bromo-elpasolites Cs₂NaGdBr₆: Ce³⁺ (CNGB: Ce³⁺) are presented. Single crystals of CNGB: Ce³⁺ with dimensions up to Ø7×10 mm³ are successfully grown by the Bridgman technique. X-ray excited luminescence measurements of the grown samples showed a broad emission band in the wavelength range from 365 to 470 nm. It offered an energy resolution of 5.1% (FWHM) at 662 keV for 10% Ce sample. The light output of the investigated samples increases along with cerium concentration. A maximum light yield of ～36,800 ph/MeV is measured for the 10% Ce sample crystal. Under γ-ray excitation, CNGB: Ce³⁺ crystals showed three exponential decay time components. The scintillation mechanism in the sample crystal is presented.     

Determination of the scintillator decay time by the autocorrelation method

An autocorrelation method is developed for determining the composition and decay time of scintillators. This method also allows studying the spatial distribution of nuclear radiation and controlling the amount of the dopants introduced in the scintillator. The decay time is measured from a few nanoseconds to microseconds. It is found out that the decay time increases in plastic scintillators with a wavelength shifter and a Gd doped.     

Improvement of the scintillation properties of Gd3Ga3Al2O12:Ce,B single crystals having tailored defect structure

A novel approach is reported to minimize various defect centers in Ce doped Gd₃Ga₃Al₂O₁₂ single crystals to improve the scintillation properties. The crystals of Gd₃Ga₃Al₂O₁₂ codoped with 0.2 at% Ce and B (GGAG:Ce,B) have been grown in air and argon ambient using the Czochralski technique. The scintillation light output of crystals grown in Ar ambient was significantly increased after annealing the crystals in air. The measured light output of 60000 ph/MeV for annealed crystals is the highest value reported among this class of materials. As a consequence, the energy resolution at 662 keV gamma‐rays from a ¹³⁷Cs source was improved from 8% for the crystals grown in air to 6% for crystals grown in Ar and subsequently annealed in air. Further, the thermal quenching energy of photoluminescence (PL) emission was increased to be 470 meV for the annealed crystals. The thermoluminescence (TL) measurements suggest that the crystals grown in Ar ambient and post‐growth annealed in air may have a lesser concentration of trap centers which subsequently lead to the improvement in optical and scintillation properties leading to a superior detector performance. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Crystal growth and characterization of CsSr1–xEux I3 high light yield scintillators

In this work, we report on single crystal growth and characterizations of a new scintillation material: CsSr_1–xEu_x I₃ (0 ≤ x ≤ 1). Single crystals of CsSr_0.99Eu_0.01I₃, CsSr_0.92Eu_0.08I₃ and CsEuI₃ were grown via the Vertical Gradient Freeze method. The crystals exhibit good crystal quality, high light yield, and excellent energy resolution. Initial results show that the scintillation light yield of our CsSr_0.92Eu_0.08I₃ crystal is ～65,000 ph/MeV with 5.9% energy resolution at 662 keV. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)