Time-resolved measurement of atomic emission enhancement by fs--ns dual-pulsed laser-induced breakdown spectroscopy

Time-resolved measurement of atomic emission enhancement is performed by using a 500-fs KrF laser pulse incident upon a high density supersonic O_{2} gas jet, synchronized with an orthogonal ns frequency-doubled Nd:YAG laser pulse. The ultra-short pulse serves as an igniter of the gas jet, and the subsequent ns-laser pulse significantly enhances the atomic emission. Analysis shows that the contributions to the enhancement effect are made mainly by the bremsstrahlung radiation and cascade ionization.     

Thermal desorption characteristic of helium ion irradiated nickel-base alloy

The nickel-base alloy is one of the leading candidate materials for generation IV nuclear reactor pressure vessel.To evaluate its stability of helium damage and retention,helium ions with different energy of 80 keV and 180 keV were introduced by ion implantation to a certain dose(peak displacement damage 1-10 dpa).Then thermal desorption spectroscopy(TDS)of helium atoms was performed to discuss the helium desorption characteristic and trapping sites.The desorption peaks shift to a lower temperature with increasing dpa for both 80 keV and 180 keV irradiation,reflecting the reduced diffusion activation energy and faster diffusion within the alloy.The main release peak temperature of 180 keV helium injection is relatively higher than that of 80 keV at the same influence,which is because the irradiation damage of 180 keV,helium formation and entrapment occur deeper.The broadening of the spectra corresponds to different helium trapping sites(He-vacancies,grain boundary)and desorption mechanisms(different Hen Vm size).The helium retention amount of 80 keV is lower than that of 180 keV,and a saturation limit associated with the irradiation of 80 keV has been reached.The relatively low helium retention proves the better resistance to helium bubbles formation and helium brittleness.     

低能量阈HPGe探测器测量WIMPs

建立了一套用于暗物质WIMPs粒子直接探测研究的低本底、低能量阈高纯锗探测器,探测器质量为5g,能量阈可以达到100eV.基于标准模型的最小超对称性扩展理论(MSSM),讨论了该探测器可能研究的超对称参数空间.研究结果表明,在WIMPs较小质量区域,这一实验可能给出WIMPs与锗核相互作用截面的最低上限     

Synthesis,Crystal Structure and DNA Interaction of N-（Benzimidazol- 2-ylmethyl）-5-chlorosalicylideneimine

The title compound, N-（benzimidazol-2-ylmethyl）-5-chlorosalicylideneimine, has been synthesized and characterized by X-ray single-crystal diffraction. It crystallizes in the monoclinic system, space group P21/n, with a = 8.3765（2）, b = 18.1398（4）, c = 9.4764（3）А, β= 112.141（2）°, V= 1333.74（6）А^3, Mr = 285.73, Z = 4, Dc = 1.423 g/cm^3, F（000） = 592,/z = 0.285 mm^-1, the final R = 0.0538 and wR = 0.1456 for 1917 observed reflections with I〉2σ-（I）. The fluorescence quenching of the title compound by DNA with Stern-Volmer constant of 2.8×104 M^-1 indicates that it binds to double-stranded DNA in a partial intercalation mode.     

Developing cold-resistant high-adhesive electronic substrate for WIMPs detectors at CDEX

Herein we report a prototypical electronic substrate specifically designed to serve the weakly interacting massive particles(WIMPs)detectors at the China Dark Matter Experiment(CDEX).Because the bulky high-purity germanium(HPGe)detectors operate under liquid-nitrogen temperatures and ultralow radiation backgrounds,the desired electronic substrates must maintain high adhesivity across different layers in such cold environment and be free from any radioactive nuclides.To conquer these challenges,for the first time,we employed polytetrafluoroethylene((C2F4)n)foil as the base substrate,in conjunction with ion implantation and deposition techniques using an independently developed device at Beijing Normal University for surface modification prior to electroplating.The remarkable peeling strengths of 0.88±0.06 N/mm for as-prepared sample and 0.75±0.05 N/mm for that after 2.5-days of soaking inside the liquid nitrogen were observed,while the regular standards commonly require 0.4 N/mm^0.6 N/mm for electronic substrates.     

暗物质寻找实验中CsI（T1）晶体反符合探测器实验研究

一个正在建设的位于韩国Y2L地下实验室的低能暗物质探测实验中,采用了CsI（T1）晶体反符合探测器作为主动屏蔽体.本工作对CsI（T1）晶体反符合探测器的实验性能进行了研究.通过FADC系统记录的脉冲波形数据,研究了探测器的能量分辨率和波形甄别的能力;研究相同能量γ射线入射到反符合探测器不同位置的相对光输出将有助于选择探测器的工作参数;为了解晶体自身放射性对暗物质测量的影响,利用低本底HPGe探测器对CsI（T1）晶体内部的放射性进行了测量,得到晶体内部Cs同位素的放射性活度.探测器系统进行了约18d的试运行取数.实验数据表明,CsI（T1）晶体探测器的反符合效率约为31%,HPGe探测器的本底计数率水平约为133cpd.为了进行暗物质探测研究,需要采取有效的方法进一步降低探测器的本底水平.     

MRPC宇宙线测试及温度效应

建造了一套MRPC单元的宇宙线测试系统.在数据处理过程中实现对入射宇宙线的方向选择.实验结果表明:MRPC的时间分辨可以达到约84ps,对应的触发系统参考时间分辨可以达到约75ps.对MRPC的温度特性进行了研究,得到了一些初步结论.     

缬氨酸Schiff碱和N,N’-杂环碱三元铜配合物的合成、 晶体结构及与BSA作用

合成了铜与水杨醛缩缬氨酸Schiff碱(salval)分别和1,10-菲咯啉(phen)及2,2’-联吡啶(bpy)形成的三元配合物[Cu(salval)(phen)] (1), [Cu(salval)(bpy)]•3H2O (2). 通过元素分析, 摩尔电导, IR, UV, TG-DTG对其进行了表征. 配合物2的结构经X射线单晶衍射确定, 三斜晶系, P-1空间群: a＝0.92676(3) nm, b＝1.03143(4) nm, c＝1.25042(3) nm; α＝74.108(2)°, β＝77.2240(10)°, g＝81.5880(10)°, V＝1.11642(6) nm3, Dc＝1.467 g•cm－3, Z＝2, F(000)＝514, 最后吻合因子R1＝0.0441, wR2＝0.0856 [I＞2σ(I)]. 同时用荧光法研究了配合物与牛血清白蛋白(BSA)的相互作用. 结果表明, 两种配合物对BSA的荧光都有较强的猝灭作用, 静态猝灭是引起猝灭的主要原因. 在浓度比c配合物/cBSA为0～10范围内, 配合物1和配合物2在BSA上只有1个结合位点; 25 ℃结合常数KA分别为6.50×105 (1), 4.33×105 (2) L•mol－1; 给体(BSA)与受体(配合物)间的最近距离r分别为3.85 (1), 4.26 (2) nm. 说明两种配合物都能部分插入BSA分子内部, 且配合物1与BSA的作用强于配合物2.     

Effect of the integrated time of the induced current signal on the position resolution of the RPC detector

A prototype RPC with position resolution less than 1 mm has been produced and studied. Based on this RPC detector, the effect of the width of the integrated FADC time window on the position resolution of a RPC has been studied experimentally and theoretically. The results of theoretical calculation and experimental measurement have shown good agreement.     

Systematical law of (n, γ) reaction cross sections of even-even nuclei

We have derived a formula for the neutron radiative capture cross section in the framework of a statistical model approach to nuclear reactions. Based on this formula, new systematics are established between the (n, γ) reaction cross section and the energy level density of a compound nucleus or a relative neutron excess of an even-even target nucleus for neutron incident energy above the resonance region to MeV. Good agreement with experimental data suggests that this new systematical law is helpful to analyze the experimental data.