A simulation study of the e~+/e~- sensitivity of a low resistive phosphate glass electrode in a RPC using GEANT MC

The resistivity of conventional glass is quite high and is unacceptable in a high rate environment. Low resistive glass-electrodes could be a solution for this problem. The present study reports the e+/e-simulation results of an RPC detector made from low resistive phosphate glass electrodes. The detailed geometrical configuration of the content materials which are the essential components of the glass of the RPC detector have been created with the GEANT4 simulation code. Two different types of particle sources, i.e. for e+/e-, have been located on the detectors surface to evaluate the performance of the phosphate glass RPC. Both of the particles have been simulated as a function of their respective energies in the range of 0.1 MeV – 1.0 GeV. The present simulation work has shown that the resistive electrode plays an important role for the particle production in the RPC configuration.     

New limit on Lorentz- and CPT-violating neutron spin interactions

We performed a search for neutron spin coupling to a Lorentz- and CPT-violating background field using a magnetometer with overlapping ensembles of K and 3He atoms. The comagnetometer is mounted on a rotary platform for frequent reversal of its orientation. We measure sidereal oscillations in the signal to search for anomalous spin coupling of extra-solar origin. We determine the equatorial components of the background field interacting with the neutron spin to be b?Xn=(0.1 ± 1.6) × 10?33 GeV and b?Yn=(2.5 ± 1.6) × 10?33 GeV, improving on the previous limit by a factor of 30. This measurement represents the highest energy resolution of any spin anisotropy experiment.     

Optical nonlinear characteristics of MgF_2 films containing Cu nanoparticles

An investigation is made on the optical nonlinear characteristics of MgF2 fihns containing Cu nanoparticles. When the Cu volume fraction is 0.1, at approximately εm ＋ 2εd = 0, the film exhibits a strong thirdorder optical nonlinear refractive coefficient of 1.0×10^-9 cm2/W, a nonlinear refractive index of about -4.0×10^-7 esu, a third-order optical nonlinear response of about 6.8×10^-8s esu, and a figure of merit of about 1.0×10^-11. The result shows that the film may have potential applications in optoelectronic technology.     

流动注射化学发光分析法测定蒽醌类药物

基于蒽醌类药物在碱性条件下对高碘酸钾-鲁米诺化学发光体系的化学发光信号有强烈的抑制作用这一现象,结合流动注射技术建立了一种直接测定蒽醌类药物的流动注射化学发光分析新方法。该方法测定大黄素的线性范围为1.0×10-8—3.0×10-7g/mL,检出限为2×10-9g/mL;测定大黄酸的线性范围为7.0×10-8—3.0×10-6g/mL,检出限为2×10-8g/mL;测定大黄素甲醚的线性范围为1.0×10-9—5.0×10-8g/mL,检出限为3×10-10g/mL。该方法操作简单快速、灵敏度高,可用于样品中蒽醌类药物含量的准确测定。     

八元瓜环诱导菲、芴的室温磷光研究

以八元瓜环为诱导剂、碘化钾作重原子微扰剂,在亚硫酸钠除氧下,实现了菲、芴的室温磷光发射。在该体系中菲、芴的最大激发和发射波长分别为282和509 nm,276和518 nm,磷光寿命分别为1.82和3.68 ms。在最佳实验条件下,菲在1.0×10-7～1.5×10-6mol·L-1,1.5×10-6～1.0×10-5 mol·L-1和芴在8.0×10-7～8.0×10-6mol·L-1的浓度范围内分别与其磷光强度呈良好的线性关系,检出限分别为4.8×10-9和8.0×10-9 mol·L-1。     

Experimental determination of one-and two-neutron separation energies for neutron-rich copper isotopes

A method is proposed to determine the one-neutron S_n or two-neutron S_(2n) separation energy of neutronrich isotopes.Relationships between S_n(S_(2n)) and isotopic cross sections have been deduced from an empirical formula,i.e.,the cross section of an isotope exponentially depends on the average binding energy per nucleon B/A.The proposed relationships have been verified using the neutron-rich copper isotopes measured in the 64 A Me V ~(86)Kr+~9Be reaction.S_n,S_(2n),and B/A for the very neutron-rich ~(77,78,79)Cu isotopes are determined from the proposed correlations.It is also proposed that the correlations between S_n,S_(2n) and isotopic cross sections can be used to find the location of neutron drip line isotopes.     

94MeV Xe离子辐照引起的薄膜硅光学带隙变化研究

室温下,用94MeV的Xe离子辐照纳米晶和非晶硅薄膜以及单晶硅样品,辐照量分别为1.0×1011,1.0×1012和1.0×1013ions/cm2。所有样品均在室温下用UV/VIS/NIR光谱仪进行检测分析。通过对比研究了纳米晶、非晶、单晶硅样品的光学带隙随Xe离子辐照量的变化。结果表明,不同结构的硅材料中Xe离子辐照引起的光学带隙变化规律差异显著:随着Xe离子辐照量的增加,单晶硅的光学带隙基本不变,非晶硅薄膜的光学带隙由初始的约1.78eV逐渐减小到约1.54eV,而纳米晶硅薄膜的光学带隙则由初始的约1.50eV快速增大至约1.81eV,然后再减小至约1.67eV。对硅材料结构影响辐照效应的机理进行了初步探讨。     

金等离子体的荷态分配数的计算

在非局域热动力学平衡(Non-LTE)下,采用类氢近似,计算得出电子密度分别为6.0×10~(20) cm~(-3)、1.4×10~(21) cm~(-3)、1.0×10~(22) cm~(-3)和1.7×10~(22) cm~(-3)的条件下的三体复合、辐射复合、双电子复合系数随电子温度的变化,得出总的复合系数随电子温度的变化关系;结合相关的电离系数得出相应的离子占有数的比,最后,计算出一定电子密度和温度条件下Au~(48+)～Au~(52+)离子的离子丰度,从而得到金等离子体的荷态分配数与电子温度和电子密度的关系.     

靛红-过硫酸钠体系催化动力学光度法测定土壤中镍(Ⅱ)

基于聚乙二醇(PEG)对Ni2+催化过硫酸钠(Na2S2O8)氧化靛红褪色反应的增敏效果,建立了一种新的测定Ni2+的增敏动力学光度法。确定了最佳的褪色反应条件为:1.0×10-3mol/L靛红2mL、4.0×10-3mol/LNa2S2O81.5mL、PEG4000.5mL;反应温度为75℃。该方法的线性范围为1.0—10.0μg/25mL,检出限为4.8×10-2μg/mL。催化反应为一级反应,表观活化能为58.17kJ/mol,表观反应常数为2.15×10-4s-1。方法用于土壤中镍测定,结果满意。     

The study of spallation reactions, neutron production, and transport in a thick lead target and a uranium blanket during 1.5 GeV proton irradiation

The Neutron Activation Analysis Method was used to study neutron field in a setup consisting of a thick lead target and a natural uranium blanket. This setup was exposed to 1.5 GeV proton beam from the Nuclotron accelerator. By means of gamma-ray spectroscopic measurements we determined the yields of various nuclear reactions induced in the radio-chemical sensors. The data obtained were then compared with the results of a MCNPX simulation.     

A simulation study of the e~+/e~- sensitivity of a low resistive phosphate glass electrode in a RPC using GEANT MC

The resistivity of conventional glass is quite high and is unacceptable in a high rate environment. Low resistive glass-electrodes could be a solution for this problem. The present study reports the e+/e-simulation results of an RPC detector made from low resistive phosphate glass electrodes. The detailed geometrical configuration of the content materials which are the essential components of the glass of the RPC detector have been created with the GEANT4 simulation code. Two different types of particle sou...     

用于反应堆中子/γ 射线混合场测量的涂硼电离室性能

近年来,涂硼电离室已逐渐成为核反应堆周围大通量中子/γ射线混合场监测的辐射探测器之一. 研制了一种高灵敏度涂硼电离室,并给出了其内部结构.用fA级弱电流放大器测得: 当涂硼电离室的工作电压在700 V以下时,漏电流小于1.0 pA; 用Am-Be中子源辐照时测得涂硼电离室的电流曲线坪长为500 V, 坪斜为3.72×10^-4 V^-1;当涂硼电离室的工作电压为400 V时, 对应漏电流为0.4 pA.测试表明涂硼电离室中子信号电流与辐照源的相对位置有关, 将Am-Be中子源置于距石蜡慢化体底部8 cm时,测得中子信号电流最大值为2.0 pA. 用¹³⁷Cs和⁹⁰Sr辐照时测得涂硼电离室γ射线信号电流为 1.0---2.0 pA,但在γ射线场中坪特性不如中子场中坪特性明显. 电离室中子探测灵敏度达1.0×10^-15 Acm²s量级, γ射线探测灵敏度达9.0× 10^-22 Acm²s·eV^-1量级. 这种涂硼电离室漏电流小、灵 敏度高、坪特性好,可用于反应堆周围的中子/γ射线混合场测量.     

Background neutron in the endcap and barrel regions of resistive plate chamber for compact muon solenoid/large hadron collider using GEANT4

In this study the performance of double gap RPC has been tested by GEANT4 Monte Carlo simulation code. The detector response calculations taken as a function of the neutron energy in the range of 0.01 eV-1 GeV have been simulated through RPC set-up. In order to evaluate the response of detector in the LHC background environment, the neutron spectrum expected in the CMS muon endcap and barrel region were taken into account. A hit rate of about 165.5 Hz cm⁻², 34 Hz cm⁻², 33.6 Hz cm⁻², and 27.0 Hz cm⁻² due to an isotropic neutron source is calculated using GEANT4 standard electromagnetic package for a 20 × 20 cm² RPC in the ME1, ME2, ME3 and ME4, respectively. While for the same neutron source and using GEANT4 package a hit rate of about 0.42 Hz cm⁻², 0.7182 Hz cm⁻² was measured for the MB1 and MB4 stations respectively. Similar characteristics of hit rates have been observed for GEANT4 low electromagnetic package.      

Measurement of the positive muon lifetime and determination of the Fermi constant to part-per-million precision

We report a measurement of the positive muon lifetime to a precision of 1.0 ppm; it is the most precise particle lifetime ever measured. The experiment used a time-structured, low-energy muon beam and a segmented plastic scintillator array to record more than 2×10(12) decays. Two different stopping target configurations were employed in independent data-taking periods. The combined results give τ(μ(+)) (MuLan)=2?196?980.3(2.2) ps, more than 15 times as precise as any previous experiment. The muon lifetime gives the most precise value for the Fermi constant: G(F) (MuLan)=1.166?378?8(7)×10(-5) GeV(-2) (0.6 ppm). It is also used to extract the μ(-)p singlet capture rate, which determines the proton's weak induced pseudoscalar coupling g(P).     

长周期光纤光栅气敏薄膜传感器结构优化

基于三包层长周期光纤光栅模型,研究了包层表面涂覆一层溶胶凝胶气敏薄膜的长周期光纤光栅化学传感器的灵敏度Sn与薄膜光学参量(折射率n3和厚度h3)和光纤光栅结构参量(光栅周期、折变量和光栅长度)之间的关系。采用最优化数值方法,找到了获得高灵敏度所需的最佳膜层光学参量和光栅结构参量。理论计算表明,该类型传感器对膜层折射率的测量分辨率高达10-8。实验上制作了对乙醇气体敏感的传感器,并证实了传感器结构优化的必要性。     

石英粉/磷酸盐缓冲溶液体系中羟自由基荧光分光光度法定量检测研究

为了定量检测石英粉/磷酸盐缓冲溶液体系中极低浓度的羟自由基(·OH),依据对苯二甲酸(TA)在pH中性的缓冲溶液中与羟自由基反应生成唯一稳定且具有很强荧光特性的产物即2-羟基对苯二甲酸(HOTP),本文建立了滤液最大激发/发射波长EX_max/EM_max=316 nm/422 nm处的荧光强度与HOTP浓度关系的标准曲线,通过检测石英粉与缓冲溶液作用之后滤液的荧光强度,从而间接测定了体系产生的·OH累积浓度。通过重复试验并分析五个不同实验条件下体系产生的·OH累积浓度,最小检出限达到1.59×10-10 mol·L-1,相对偏差为1.20%~7.89%,标准偏差为1.09×10-9~2.17×10-9 mol·L-1,相对标准偏差为3.5%~5.8%,说明该方法具有较高的精确度和较好的重复性。该方法可用于定量检测pH中性溶液中极低浓度的·OH,与其他方法相比,具有明显的检测限低、成本低、灵敏度高、稳定性和重现性好等优势。     

光电倍增管中子直照灵敏度响应

 光电倍增管的中子直照响应对脉冲中子探测器的设计和实际应用具有重要影响。分析了中子束直接照射光电倍增管产生直照响应的过程和机理。中子与光电倍增管入射窗硼硅玻璃中的硼和硅发生(n,α)和(n,p)反应,导致窗玻璃产生荧光,从而使光阴极发射光电子。在5SDH-2小串列加速器上,选用9815B和9850B两种光电倍增管进行实验,得到了光电倍增管的中子直照灵敏度能谱响应曲线。结果表明：中子能量由低到高变化时,光电倍增管的中子直照灵敏度也随之增大;两种光电倍增管的中子直照灵敏度比值为1.9×10²~2.74×10²,该值与其相应的增益比量级一致。     

Search for sub-eV mass solar axions by the CERN Axion Solar Telescope with 3He buffer gas

The CERN Axion Solar Telescope (CAST) has extended its search for solar axions by using (3)He as a buffer gas. At T=1.8 K this allows for larger pressure settings and hence sensitivity to higher axion masses than our previous measurements with (4)He. With about 1 h of data taking at each of 252 different pressure settings we have scanned the axion mass range 0.39 eV?m(a)?0.64 eV. From the absence of excess x rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of g(aγ)?2.3×10(-10) GeV(-1) at 95% C.L., the exact value depending on the pressure setting. Kim-Shifman-Vainshtein-Zakharov axions are excluded at the upper end of our mass range, the first time ever for any solar axion search. In the future we will extend our search to m(a)?1.15 eV, comfortably overlapping with cosmological hot dark matter bounds.     

用于位置灵敏型中子探测器的6LiF/ZnS（Ag）闪烁体性能研究

研究了掺杂6LiF的ZnS(Ag)闪烁体对中子、γ射线的发光特性和EJ426闪烁体样品的热中子探测效率、出射光产额和γ灵敏度。EJ426的热中子探测效率为32.4%,出射光产额为8.01×103光子/中子,70 mV阈值时的γ灵敏度小于10-7,表明EJ426是较理想的闪烁体型位置灵敏中子探测器材料。     

化学发光法测定甲萘威

在NaOH介质中,铁氰化钾氧化鲁米诺产生化学发光,甲萘威对该发光反应有较强的抑制作用且抑制发光强度与甲萘威的浓度呈较好的线性关系,基于此性质建立了测定甲萘威的新方法。在实验的优化条件下,测定甲萘威的检出限为5.5×10-11mol.L-1,线性范围为1.5×10-10—4.0×10-8mol.L-1,对5.0×10-9mol.L-1甲萘威进行了11次平行测定,其RSD为1.74%。该法用于合成样品中甲萘威的测定,结果令人满意。