CeF3闪烁探测器对五种能量中子的甄别能力研究

用CeF3闪烁体和常用闪烁体ST401分别配特性相同的光电倍增管构成两种闪烁探测器,在1.2MeV、2.5MeV、3.5MeV、5.0MeV和14MeV等能量的稳态中子源场中,测量了这两种闪烁体探测器的电流输出,得到结果表明:上述能量的中子与CeF3闪烁探测器作用形成的电流比同尺寸ST401闪烁体构成探测器的输出电流均低一个量级以上,这些结果与这两种探测器在钴、铯γ源中测量结果比较,可以得出在n、γ混合辐射场中测量γ辐射时,CeF3闪烁探测器能够较好地屏蔽这些能量中子的干扰.     

国产YAP:Ce闪烁晶体的相对探测能力测量

为适应在n、γ混合脉冲辐射场中对低强度快脉冲γ辐射测量的需要,近年国内新研制出实用型YAlO3:Ce(YAP:Ce)快响应无机闪烁晶体.我们使用脉冲线性电流大于1.5 A的光电倍增管,分别配置这种晶体以及CeF3、NaI等晶体构成闪烁探测器,在放射性标准源场中,对晶体的相对探测能力进行测量.测量结果表明:国产新型YAP:Ce无机晶体对这1.25 MeV 射线的探测能力比同体积的CeF3平均高一个量级,是同体积NaI的40;左右;当晶体厚度小于2 mm时,YAP:Ce与CeF3、NaI的输出比值分别大于16和44;,说明厚度越薄晶体的相对探测能力越强.     

几种有机、无机晶体相对灵敏度和时间特性测量实验

在进行中子/γ粒子测量时,一般采用致电离辐射探测器进行测量.闪烁体作为致电离辐射探测器的重要组成部分,需对闪烁体的特性进行实验测量.本文总结了在СГС-67型三通道γ加速器和DPF中子源上进行的NaI(Tl)、CeF3、PbWO4晶体的灵敏度、时间响应等特性的标定实验,分析了实验现象,合理地处理数据,给出了实验结果.     

大面积LaBr3:Ce闪烁探测器伽马灵敏度和时间响应测量

在60Co放射性标准源场中,对国内新研制的大面积LaBr3∶Ce闪烁探测器伽马灵敏度进行了测量,并用GD100光电管分别与LYSO:Ce、ST401闪烁体构成闪烁探测器的伽马灵敏度进行了对比分析;应用CΓC-67型三通道的ns快脉冲辐射源对这种大面积新型闪烁晶体本身的时间响应特性进行了测量.实验测量结果表明:直径76 mm的大面积LaBr3∶Ce闪烁探测器伽马灵敏度与LYSO∶Ce、ST401闪烁探测器的同体积归一灵敏度比分别超过5和200;时间响应前沿2.56 ns,后沿56 ns,半高宽23.56 ns,衰减时间25.45 ns.     

YAP∶Ce晶体伽玛能响及抗中子能力研究

YAlO3∶Ce(YAP∶ Ce)是近年国内新研制出的实用型快响应无机闪烁晶体.本工作针对YAP∶ Ce晶体与光电倍增管组合构成闪烁探测器,根据闪烁体沉积能量与质能吸收系数等相关参数的核物理理论关系,通过解析方法计算了多种γ能量对应的灵敏度,同时应用Monte Carlo方法模拟,获得了YAP∶ Ce晶体对γ射线的能量响应理论趋势;并通过实验测量了该探测器对γ和中子多种能量点的灵敏度,以检验理论和模拟计算的可靠性.理论和实验结果表明:YAP∶ Ce闪烁探测器0.3 MeV～ 1.25 MeV能区γ灵敏度随能量的增加而平缓地增加;其中1.25 MeV能量的灵敏度比0.37 MeV能量的灵敏度高约70;;同时具有较强的抗中子干扰能力:1.25 MeV的γ灵敏度与DT(14.1 MeV)中子灵敏度相当,比DD(2.54 MeV)中子灵敏度高5倍多;并且实验结果与理论计算、M.C模拟结果差异在5;范围内.     

低强度脉冲伽马辐射测量中LaCl_3、YAG∶Yb和CeF_3闪烁探测器优选

为了在低强度脉冲伽马辐射测量中获得更精密可靠的测试数据,对La Cl3(50 mm×30 mm)、YAG∶Yb(50mm×50 mm)两种新型闪烁探测器和常用Ce F3(45 mm×20 mm)闪烁探测器的灵敏度、伽马/中子甑别能力、时间响应特性、统计涨落等主要参量进行了实验测量和对比。实验测量结果表明:La Cl3闪烁探测器灵敏度最高;伽马/中子甑别能力比另两种闪烁探测器高1倍以上;时间响应与Ce F3闪烁探测器相当;统计涨落最小(测点注量率相当的情况下)。进行中子、伽马混合脉冲辐射场中的低强度脉冲伽马辐射测量时,三种闪烁探测器中,La Cl3闪烁探测器是一种更佳的实用候选闪烁探测器。     

国产无机闪烁晶体LaCl_3∶Ce的探测能力和时间响应测量

以国产的掺铈氯化镧(LaCl3:Ce)闪烁晶体与线性电流大于1.5 A的光电倍增管构成闪烁探测器,利用 60Co、137Cs放射性标准源场,实验测量这种探测器对γ辐射的探测能力,并与同情况NaI:Tl闪烁探测器进行比对;利用266 nm单色激光和ns级的γ脉冲辐射分别对这种闪烁体的光致激发、辐射激发的时间响应性能进行测量.测量结果表明:国产新型LaCl3:Ce无机闪烁晶体样品构成的探测器对1.25 MeV 、0.66 MeV γ射线的探测能力平均约为同情况NaI:Tl闪烁探测器的103%,高的已超过了同尺寸NaI:Tl构成的闪烁探测器;266 nm单色激光光致激发时间响应波形前沿、半高宽、后沿和衰减常数分别为1.05 ns、17.42 ns、54.30 ns和24.61 ns,ns级的γ脉冲辐射激发的时间响应波形前沿、半高宽、后沿和衰减常数分别为1.52 ns、21.99 ns、75.13 ns和34.19 ns.     

强辐射对Yb∶YAG超快无机闪烁探测器灵敏度影响的实验测量

为了给强脉冲辐射场中应用超快闪烁探测器进行精密物理测试以及相关晶体抗核加固提供实验测量数据参考,针对近年新研制的Yb∶ YAG超快无机闪烁体与GD40光电管构成的快闪烁探测器,在源强近万居的强稳态辐照场中,细致测量了辐射累计伽马剂量从约1 Gy开始到最高约1 kGy全过程中Yb∶ YAG超快闪烁探测器输出电流的变化数据;在测点注量率大于1017cm-2·s-1的“强光一号”短γ脉冲辐射场中,测量了Yb∶ YAG超快闪烁探测器输出脉冲波形响应情况.实验测量结果表明:在强稳态辐射场情况下,对应累计剂量5 ～ 10Gy时,YAG(Yb)闪烁探测器灵敏度下降约5～10;(相对辐照IGy时的情况);测点累计伽马剂量约1 kGy时,Yb∶ YAG超快闪烁探测器的电流输出与约1 Gy时的比值约50;;短γ脉冲辐射情况下,测点累计注量约4×109 cm-2,Yb∶ YAG超快闪烁探测器输出电流约1A时,灵敏度下降约10;(相对累计注量约3×109 cm-2的情况),当测点注量大于1010 cm-2(累积剂量超过100 mGy),Yb∶ YAG超快闪烁探测器会出现较明显的损伤现象.     

Cs2LiYCl6∶Ce晶体的n/γ双探测闪烁性能研究

Cs₂LiYCl₆∶Ce(CLYC)晶体是一种具有n/γ双探测能力的新型闪烁晶体。采用坩埚垂直下降法生长出富⁶Li的CLYC晶体毛坯,经加工、封装得到φ50 mm×50 mm的CLYC闪烁晶体封装件,其对¹³⁷Cs 662 keV γ射线的能量分辨率为4.22%;测量²⁵²Cf中子源的脉冲波形甄别(PSD)品质因子(FOM)为3.45。凭借其优异的性能,CLYC闪烁晶体有望在中子探测领域替代³He正比计数管,并可作为n/γ双探测的优选材料,应用于中子辐射探测器、放射性同位素识别仪、个人辐射剂量仪,以及其他中子、伽马射线的探测。     

LaBr3:Ce闪烁晶体的生长及性能研究

掺铈溴化镧(LaBr3:Ce)闪烁晶体具有光输出高、衰减时间短、能量分辨率高等优异特性,在核医学成像、地质勘探、石油测井、空间物理等核辐射探测领域具有广阔的应用前景.本文采用改进的坩埚下降法,利用自发成核成功地生长了Ce3+掺杂浓度5.0at;、尺寸φ50 mm×60 mm的LaBr3:Ce闪烁晶体,测试了晶体的光输出、能量分辨率和衰减时间等闪烁性能.结果表明,在137Cs(662 keV)放射源作用下,LaBr3:Ce晶体的光输出为同体积NaI:Tl晶体的155;,能量分辨率为3.3;,衰减时间为25 ns.     

Triethyl ammonium salt of O,O′-bis(p-tolyl)dithiophosphate, [Et3NH]+[(4-MeC6H4O)2PS2]−

Triethyl ammonium Salt of O,O′-bis(p-tolyl)dithiophosphate and O,O′-bis(m-tolyl)dithiophosphate have been obtained by reaction of p- and m-cresol, respectively with P₂S₅ in toluene and have been characterized by elemental analysis, IR, ¹H and ³¹P NMR spectroscopy. The molecular structure of O,O′-bis(p-tolyl)dithiophosphate has been determined. Crystal data: [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻: Monoclinic, P2₁/c, a=15.2441(9) ?, b=10.415(2) ?, c=3.9726(9) ?, β=91.709(7)°, V=2217.5(1) ?⁻³, Z=4.Supplementary materials Additional material available from the Cambridge Crystallographic Data Centre (CCDC no. 600927 for [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻ comprises the final atomic coordinates for all atoms, thermal parameters, and a complete listing of bond distances and angles. Copies of this information may be obtained free of charge on application to The Director, 12 Union Road, Cambridge CB2 2EZ, UK (fax: +44-1223-336033; email: deposit@ccdc.cam.ac.uk or www:http://www.ccdc.cam.ac.uk).     

First-principles coexistence simulations of supercooled liquid silicon

We perform first-principles coexistence simulations of the low-density and the high-density phases of supercooled liquid silicon and find a negative slope for the coexisting line in the temperature-pressure plane. Electron density maps and electron-localization function plots of the two phases of silicon show marked differences. The calculated differences suggest more localized electrons in the low-density liquid compared to the high-density liquid, coming from an increased population of covalent bonds, which further explain the calculated negative slope in the two phase coexistence regime. This is consistent with the presence of a pseudo-gap in low-density liquid silicon, absent in the high-density liquid which shows a metallic behavior.     

Crystal structures of thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane

Structures of both thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane, ?C₆H₄?CH₂SCH₂?C₆H₁₀?CH₂SCH₂?, have been determined, wherecis andtrans refer to the attachments to the cyclohexane ring. Thecis form crystallizes in the monoclinic space groupP2₁/c witha=8.4299(11)Å,b=21.772(2)Å,c=8.9724(13)Å, β=116.574(11)^o, andZ=4. Thetrans isomer packs into the monoclinic space groupP2₁ witha=8.159(16)Å,b=10.185(5)Å,c=9.558(2)Å, β=112.435(18)^o, andZ=2. The cyclohexane ring of thecis isomer is in the chair conformation, while the cyclohexane of thetrans isomer is found in a twisted boat conformation.     

CTAB与SDBS对碳酸锶粒子生长形态调控及机理研究

以表面活性剂CTAB和SDBS为化学添加剂,采用化学共沉淀法对碳酸锶晶体的生长形态进行调控,成功地制备出了实心的树枝状和花瓣为空心的花状碳酸锶粉体,并用X射线衍射(XRD)、扫描电子显微镜(SEM)和傅里叶变换红外光谱(FT-IR)等分析手段对样品进行了表征;最后重点对化学添加剂可能产生的影响机理进行了初步的探讨.结果表明,CTAB和SDBS在晶体生长的过程中能起到显著的影响作用,两者对粒子分散性能的作用效果相反,而且后者对晶体(013)和(213)晶面表面能降低的贡献明显大于前者.     

Crystal structure of Zn4Na(OH)6SO4Cl·6H2O

The structure of Zn₄Na(OH)₆SO₄Cl·6H₂O, a secondary mineral from Hettstedt, Germany, was determined by single-crystal X-ray diffraction. The crystals are hexagonal,a=8.413(8),c=13.095(24) Å, space group $P\bar 3$ , Z=2. The structure was refined to R=0.0554 and R_w=0.0903 for 970 reflections with I≥3σ(I). The structure can be described as zinc hydroxide layers perpendicular toc, from which sulfates and chlorides extend. The layers are held together by a system of hydrogen bonds involving hexaaquo Na⁺ ions which occupy the interlayer space.     

Synthesis and Crystal Structure of 5-[2-(6-bromonaphthalenyloxymethyl)]-3-(4-morpholinomethyl)-1,3,4-oxadiazole-2(3<Emphasis Type="Italic">H</Emphasis>)-thione

Abstract  The title compound, C₁₈H₁₈BrN₃O₃S, a derivative of 1,3,4-oxadiazole, crystallizes in the triclinic space group P-1 with unit cell parameters a = 6.8731(3), b = 8.9994(4), c = 15.7099(6) ?, α = 92.779(3)°, β = 130.575(3)°, γ = 107.868(4)°, Z = 2. The dihedral angle between the mean planes of the planar naphthyl and morpholine (chair) rings with the planar oxadiazol ring is 50.1(8) and 76.8(6)°, respectively. The planar naphthyl ring is twisted 52.2(5)° with the mean plane of the morpholine ring. A group of four intermolecular close contacts are observed between a bromine atom and hydrogen atoms from the closely packed naphthyl, morpholine and oxy–methyl groups in the unit cell. These molecular interactions in concert with an additional series of π–π stacking interactions that occur between the center of gravity of the two 6-membered rings of the naphthalene group influence the twist angles of each of these three groups. A MOPAC AM1 calculation of the conformation energy of the crystal structure [226.0128(9) kcal] compared to that of the minimum energy structure after geometry optimization [29.9744(1) kcal] reveals a significantly reduced value. The twist angles of the three groups above also change after the AM1 calculation giving support to the influence of both intermolecular C–H···Br short-range interactions and Cg π–π stacking interactions on these angles which therefore play a role in stabilizing crystal packing. Graphical Abstract  Crystal structure of 5-{[(6-bromonaphthalen-2-yl)oxy]methyl}-3-(morpholin-4-ylmethyl)-1,3,4-oxadiazole-2(3H)-thione, C₁₈H₁₈BrN₃O₃S, is reported and its geometric and packing parameters described and compared to a MOPAC computational calculation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Crystal structure of irisolidone from the flowers of Pueraia lobata

Irisolidone (5,7-dihydroxy-6,4′-dimethoxyisoflavone) was isolated from the flowers of Pueraia lobata and its crystal structure was examined by X-ray single crystal diffraction. The crystal structure of irisolidone is monoclinic, space group P2₁/c with a = 15.491(9) ?, b = 7.895(4) ?, c = 13.321(7) ?, β = 110.546(9)° and Z = 4. Hydrogen bonding and aromatic π–π stacking assemble the title compound into a three-dimensional networking structure.     

Synthesis of spinacine and spinacine derivatives: crystal and molecular structures of Nπ-hydroxymethyl spinacine and Nα-methyl spinaceamine

The natural amino acid L-Spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) has been synthesized following a new pathway which gives a chemically and optically pure product with an excellent yield. The crystal structures of a synthetic intermediate, N^π-hydroxymethyl-spinacine, and a spinacine derivative, N^α-methyl-spinaceamine, have been investigated through X-ray diffraction: Spi(πMeOH)·H₂O, monoclinicP2 _i,a=8.571(1),b=6.682(1),c=8.588(1) Å, and β=94.67(1)^o. Spm(αMe)·2HCl·H₂O, triclinicP l,a=7.492(4),b=10.799(3),c=7.040(2) Å, α=91.88(2), β=98.36(3) and γ=73.34(3)^o. Spi(πMeOH) crystallizes with a water molecule and displays a zwitterionic character. The carboxylate group is in equatorial position and forms a short electrostatic interaction of 2.618(2) Å between one of its oxygens and the protonated nitrogen of the tetrahydropyridine ring. The crystal packing is assured by strong O?H???O, O?H???N, N?H???N intermolecular hydrogen bonds and C?H???O close contacts. The biprotonated compounds Spm(αMe) crystallizes with two Cl^? anions and a water molecule. The positive charge on the imidazole ring is delocalized on the conjugated moiety N=C?N. The crystal is built up by clusters formed by two biprotonated Spm(αMe) molecules, four Cl^? anions and two water molecules linked together by hydrogen bonds.