高电荷态离子与Si(110)晶面碰撞的沟道效应研究

不同电荷态低速离子(Ar^q+,Pb^q+)轰击Si(110)晶面,测量不同入射角情况下的次级粒子的产额. 通过比较溅射产额与入射角的关系,证实沟道效应的存在. 高电荷态离子与Si相互作用产生的沟道效应说明溅射产额主要是由动能碰撞引起的. 在小角入射条件下,高电荷态离子能够增大溅射产额. 当高电荷态离子以40°—50°入射时,存在势能越高溅射产额越大的势能效应. 关键词： 高电荷态离子 溅射 沟道效应     

高电荷态离子与SiO2表面相互作用的研究

高电荷态离子(Pbq ,Arq )由兰州近代物理研究所的ECR实验平台所产生,轰击非晶态SiO2表面.用微通道板测量溅射粒子产额的角分布.用公式拟合实验溅射角分布得到了较好的结果,并给出了初步的理论解释.由此得出了高电荷态离子与SiO2表面作用的微分溅射截面.实验结果表明高电荷态离子能够增加动能溅射;同时高电荷态离子入射能够引起势能溅射.在大角度入射时,溅射产额主要是由碰撞引起的;在小角入射时势能溅射所占比重会增大.     

Study of the PIN detector's radiation tolerance

PIN detectors have been extensively used to detect charged particles and X-ray. The new type PIN detectors were irradiated by different energy protons, and their irradiation tolerance was investigated. Relative charge collection efficiency, energy spectrometer and relative energy resolution were also measured. With the increasing of irradiation dose, charge collection efficiency decreased and relative energy resolution grown. The results suggested that the irradiation tolerance in the PIN detector depended on the range of the protons in the detector. The maximum tolerance irradiation doses of the detector for the impacts of 3.5 and 7.2 MeV protons were 3×10¹⁰p/cm² and 7.2×10⁹p/cm², respectively.     

Effect of deuteron density distribution on the deduction of screening potential from the D（d,p）T reaction in Be metals

The D(d,p)T reaction in Be metal environments has been measured to investigate the electron screening effect in metals in an energy region of from 5.5 keV to 10 keV in a center of mass system (CMS) at a temperature of 121 K. The depth distribution of deuteron density in Be metals has an impact on the observed reaction yields. A model of deuteron density distribution in metal has been proposed to obtain the original yields. A screening energy of (116±46) eV has been obtained with the assumed deuteron density distribution model.     

Energy calibration of tagged photons by the d（γ,π~-pp） reaction

The energy of tagged photons, which were provided from the internal photon tagging system of the Laboratory of Nuclear Science, Tohoku University, has been calibrated using the d（γ,π-pp） reaction. Charged pions and protons in the final state were detected with the Neutral Kaon Spectrometer （NKS2）. Photon energies were obtained from the reaction of d（γ,π-pp）. The derived photon energy was consistent with the design of the tagger system and the previous measurement using electron-positron pair production. The consistency demonstrates the performance of NKS2 and the capability of the photon energy calibration using d（γ,π-pp）.     

Energy calibration of tagged photons by the d(γ,π~-pp) reaction

The energy of tagged photons, which were provided from the internal photon tagging system of the Laboratory of Nuclear Science, Tohoku University, has been calibrated using the d(γ,π-pp) reaction. Charged pions and protons in the final state were detected with the Neutral Kaon Spectrometer (NKS2). Photon energies were obtained from the reaction of d(γ,π-pp). The derived photon energy was consistent with the design of the tagger system and the previous measurement using electron-positron pair production. The...     

医用放射性同位素99Mo/99mTc生产现状和展望

99mTc是目前临床诊断应用最为广泛的医用放射性同位素。现有医用99mTc主要通过在实验堆中辐照高浓缩235U生成的99Mo衰变得到,存在工艺复杂、成本高、长距离运输损失等弊端以及核扩散风险。此外,全球实验反应堆为数不多且面临老化、退役问题,也多次因计划内的维修或意外停产事件而使99mTc供应面临困难。本文从99Mo/99mTc的供求现状入手,分析了目前供应链中存在的主要问题,重点介绍了六种传统及新型99Mo/99mTc生产技术的原理、研究进展及其经济性效益。详细评述了三种99Mo/99mTc分离纯化工艺,提出了99Mo/99mTc生产的发展趋势和展望。其中,以加速器驱动裂变低浓缩铀盐溶液的生产方式具有无反应堆、无高浓缩铀、放射性废物少等优势,是未来的重点研究方向。同时,为减少99Mo/99mTc损失,提高产品质量,开发和优化与生产体系相适应的分离纯化工艺也势在必行。中国科学院核能安全技术研究所FDS中科凤麟核能团队设计开发的一种氘氚聚变中子源驱动的99Mo次临界生产系统方案,可获得27Ci/d的99Mo产量,能满足国内一个中等省份的医疗诊断需求。     

固态同位素β源选择对直充式核电池性能的影响

直充式核电池具有工作寿命长、结构简单、开路电压高、易微型化等优点,具有广泛的应用前景。目前,国内外对直充式核电池同位素源的选择多集中在同位素β源,尚未对不同同位素β源进行系统的分析对比。针对此问题,通过理论计算及SuperMC建模处理,研究了3H（Ti3H₂）、14C,35S,45Ca,63Ni及147Pm六种固态同位素β源对直充式核电池的能量转换效率及理论输出功率的影响。结果显示,能量转换效率随源衰变粒子平均能量的升高而增大;理论输出功率及功率密度与源半衰期成反比。综合工作寿命、输出功率及能量转换效率,建议选用147Pm同位素源。