用金活化法测定加速器中子源中子注量及MCNP4C修正

在四川大学720所2.5MeV静电质子加速器上,由核反应7Li(p,n)7Be,T(p,n)3He产生中子,对中国工程物理研究院研制的新型中子探测器进行效率刻度实验中,需要知道探测器位置处的中子绝对注量,为此我们测量了0.165、0.352、0.576、1.400MeV四个能点的中子注量。测量方法采用的是金活化法,在实验测量中,由靶头材料、冷却水层和样品的包层材料等引起的多次散射效应及中子在样品中的自屏蔽效应等均对实验结果产生影响。这些因素在实验中不可避免,也难以通过实验方法扣除,因此用Monte Carlo程序MCNP4C对上述效应进行了修正计算。     

阈活化法测量重离子反应的中子能谱

本文介绍了用~(197)Au、~(32)S、~(27)Al、~(19)F、~(12)C 等阈活化片测量9.5和11.4 MeV/u的~(16)O~(+6)重离子入射厚铜靶产生的次级中子能谱的实验方法和结果。     

Phoswich探测器的重离子束测试

利用一套由１ｍｍ厚的ＰＩＬＯＴ－Ｕ和４０ｍｍ厚的ＮＥ１１５塑料闪烁体组成的Ｐｈｏｓｗｉｃｈ（光叠层望远镜）探测器测量了４０Ａｒ（２５ＭｅＶ／ｕ）＋１９７Ａｕ反应中出射的产物，粒子鉴别采用Ｐｈｏｓｗｉｃｈ的快慢成分方法．结果表明该方法能清楚地分辨出粒子的电荷．对Ｚ＝１的粒子，ｐ、ｄ和ｔ亦能分开．     

Activation cross-sections of deuteron induced nuclear reactions on gold up to 40 MeV

Cross-sections of deuteron induced nuclear reactions on gold were measured up to 40 MeV by using the standard stacked foil irradiation technique and high resolution gamma-ray spectroscopy. Experimental cross-sections and derived integral yields are reported for the ¹⁹⁷Au(d,xn)^{197m,197g,195m,195g}Hg and ¹⁹⁷Au(d,x)^{198g,196m,196g,195,194}Au nuclear reactions. The experimental data are analyzed and compared to literature and predictions of the ALICE-IPPE, EMPIRE and TALYS theoretical model codes. The application of the new cross-sections for accelerator technology, medical radioisotope production, thin layer activation and dose calculation is discussed.     

活化法测量197Au等核素的14MeV中子反应截面

采用活化法测量了197Au等核素的14MeV中子反应截面.当入射中子能量为14.75MeV时,197Au(n,2n)196Au反应截面测量结果为(2175±76)×10-31m2,并与其他测量结果和ENDF/B-6评价数据库数据进行了比较.对于结果的一些不确定度因素,采用MCNP程序进行了分析.     

EXPERIMENTS OF MeV ION BEAM INDUCED ATOMIC MIXING

An experimental apparatus for studies of MeV ion beam modification of materials has been established on a 3 MV tandem accelerator at Fudan university. A system of X-Y electrostatic scanning implantation of MeV heavy ions and in situ Rutherford. backscattering analysis was included in it. The uniformity of scanning implantation was checked by the RBS measurement of a Si wafer implanted with 1 MeV Au ions. MeV ion beam mixing of Au/Si, Au/Ge and Ag/Si systems was preliminarily studied. The samples were irradiated by certain fluences of 1 MeV Ag ions at room temperature. The mixed layers were analyzed in situ using the glancing RBS technique with 2 MeV 4He+ ions. For Au/Si system, a uniformly mixed layer with a defined composition is obtained, and the intermixing is much less for Ag/Si system than for Au/Si system.     

Measurement of fast-neutron capture cross sections for 75As

1 INTRODUCTIONThe cross sections of the "As(n,7)"As reaction are boortant in evaluating theradiation damage of the material. EXPerimeats[1-6] and evaluations have been performedto deterAnne the "As(n, 7)"As reaction cross section, but there are large discrepanciesamong them especially in the MeV neutron energy region. Therefore, new eXPerAnent isneeded.2 EXPERIMENT DETAILSThe measuremenis were perfOrmed at the 4.5 MV Van de Grand accelerator of theInstitute Of Heavy Ion Phy…     

放射性核束17N轰击9Be和197Au靶的中子发射

用飞行时间技术测得33.4MeV/u     

Energy loss of energetic Ar, Kr, Au and U ions in mylar, aluminum and isobutane

The BigSol Superconducting Solenoid Beam Line at the Texas A&M Superconducting Cyclotron has been used to measure energy losses of ⁴⁰Ar, ⁸⁴Kr, ¹⁹⁷Au and ²³⁸U ions in mylar, aluminum and isobutane at energies ranging from the Bragg peak up to several MeV/nucleon. The experimental data are compared with predictions from the SRIM code. In general experimental data for ⁴⁰Ar and ⁸⁴Kr are in agreement with model predictions whereas differences on the order of 10% are evidenced in some cases for ¹⁹⁷Au and ²³⁸U ions especially at and around the Bragg peak energies.     

Neutron yields from 155 MeV/nucleon carbon and helium stopping in aluminum

Neutron fluences have been measured from 155 MeV/nucleon 4He and 12C ions stopping in an Al target at laboratory angles between 10 and 160 deg. The resultant spectra were integrated over angle and energy above 10 MeV to produce total neutron yields. Comparison of the two systems shows that approximately two times as many neutrons are produced from 155 MeV/nucleon 4He stopping in Al and 155 MeV/nucleon 12C stopping in Al. Using an energy-dependent geometric cross-section formula to calculate the expected number of primary nuclear interactions shows that the 12C + Al system has, within uncertainties, the same number of neutrons per interaction (0.99 +/- 0.03) as does the 4He + Al system (1.02 +/- 0.04), despite the fact that 12C has three times as many neutrons as does 4He. Energy and angular distributions for both systems are also reported. No major differences can be seen between the two systems in those distributions, except for the overall magnitude. Where possible, the 4He + Al spectra are compared with previously measured spectra from 160 and 177.5 MeV/nucleon 4He interactions in a variety of stopping targets. The reported spectra are consistent with previously measured spectra. The data were acquired to provide data applicable to problems dealing with the determination of the radiation risk to humans engaged in long-term missions in space; however, the data are also of interest for issues related to the determination of the radiation environment in high-altitude flight, with shielding at high-energy heavy-ion accelerators and with doses delivered outside tumor sites treated with high-energy hadronic beams.     

Effect of MeV beams on the interface structure of metal(adlayer)-silicon (crystal substrate) systems

The influence of MeV ion beams on the measured intensity of the surface peak (SP) in channeling studies has been examined for Ag and/or Au covered Si(111), and Pd covered Si(111) systems with film thicknesses up to several monolayers. A simple phenomenological model is introduced to analyse the observed increase in atomic displacements induced by probing He ions of 1 MeV. For the Ag and Pd cases, effects attributable to the deposited metal was small while for Au an appreciable enhancement of the beam sensitivity was observed which increases with increasing Au thickness for beam doses of ? 3.1 × 10¹⁶ ions/cm². The observe differences cannot be explained by the difference in mass and atomic number of the overlayer atoms. The model suggests that the chemical nature of atomic bonds near the interface affects the damage threshold energy.     

Proposal of an Effective Initial Guess Scheme for Higher Harmonic Mode Calculation of Boiling Water Reactor Cores

Response functions of a BC501A liquid organic scintillator for neutrons up to 800 MeV have been measured at the heavy-ion accelerator of the National Institute of Radiological Sciences, Japan. A thick graphite target was bombarded with 400-MeV/u C ions and 800-MeV/u Si ions to produce high-energy neutrons whose kinetic energy was determined by the time-of-flight method. The measured response functions were compared with the results obtained using SCINFUL-QMD code, and the accuracy of the code was experimentally verified up to 800 MeV. This work will contribute to extending the energies measurable with our new radiation dose-monitoring system (DARWIN), which is based on the BC501A scintillator.     

固体气泡损伤探测器阈起源的实验判别

用500MeV/u^56Fe,650MeV/u^40Ar,600MeV/u^28Si和180MeV/u^4He对固体气泡损伤探测器（T－12型）进行了实验研究，实验结果表明，固体气泡损伤探测器的阈特性可用临界能量损失率表征，在一般条件下，限定能量损失率在不同重离子产生径迹时不具有相同的临界值，因此，不能作为径迹形成的判据。     

Measurements of induced activity in concrete by secondary particles at forward direction produced by intermediate energy heavy ions on an Fe target

Spallation and neutron capture reaction rate distributions were measured using activation detectors inside a 90-cm thick ordinary concrete pile exposed to a field of secondary particles escaping a thick (stopping length) iron target bombarded with various intermediate energy ions, 230 MeV/u He, 400 MeV/u C, and 800 MeV/u Si. Activation detectors of aluminum, bismuth, gold, and gold covered with cadmium were inserted at various depths in the concrete pile. In addition, the distributions of activation reaction rate were simulated by FLUKA and PHITS Monte-Carlo codes. Generally, comparison of measured and calculated reaction rates show agreement within a factor of two. The experimental data will be useful for benchmarking Monte-Carlo radiation transport simulation code capabilities in estimating radioactivity induced in accelerator radiation shielding.     

Energy loss of Xe-ions in thin foils

The energy loss of ¹³²Xe-ions in C, Al, Ni, Ag, Lu, Au, Pb and Th foils was measured in the energy range from 0.1 to 5 MeV/u using the TOF-E method. The results are compared with previously published data and with the predictions of several computer codes. They include theoretical codes: PASS, CASP, semi-empirical programs: SRIM, LET and the Hubert table predictions.     

~(12)C与~(209)Bi反应中Au同位素的产额与Q_(gg)的关系

用47MeV/u12C离子轰击天然铋靶,通过炮弹和靶核之间的核子转移反应产生Au同位素。使用放射化学方法从大量Bi和复杂反应产物中分离、纯化Au,并制备Au的γ射线测量源。使用HPGe探测器测量放射性Au同位素的γ活性。根据照射结束时Au同位素的活度和其他相关数据,确定每个Au同位素的产生截面。分析发现,缺中子Au同位素的产生截面与Qgg值之间不遵从指数依赖关系,这可用重离子碰撞中的次级过程加以解释。     

Measurements of the 152Srn(γ,n) Cross Section with Laser-Compton Scattering γ Rays and the Photon Difference Method

The cross sections of the ¹⁵²Sm(γ,n) and ¹⁹⁷Au(γ,n) reactions have been measured with the laser-Compton scattering (LCS) γ beam in the 8.3–12.4MeV energy range. The photon difference method has been used for LCS γ rays in the data analysis for the first time. The present data for ¹⁹⁷Au measured as the standard are in agreement with the preceding data and the recent recommendation. On the other hand, the preceding data for ¹⁵²Sm at 8.3 MeV are twice as large as the present data.     

Activation cross-sections of deuteron induced reactions on platinum

In the frame of a systematical study of light ion induced nuclear reactions on platinum activation cross-sections for deuteron induced reactions were investigated. Excitation functions were measured from the respective threshold up to 21 MeV for the ^natPt(d,x)^{192,193,194,195,196m,196}Au, ^natPt(d,x)^195m,197Pt and ^natPt(d,x)¹⁹²Ir reactions by using the stacked foil irradiation technique. Calculations of the excitation functions were performed by the ALICE-IPPE code and compared with the experimental results. The possible application of the experimental data is discussed.     

千兆电子伏重离子加速器——兰州冷却储存环

能量达千兆电子伏的兰州重离子加速器冷却储存环HIRFL-CSR,是一个集加速、累积、电子冷却及内外靶实验于一体的多功能双冷却储存环同步加速器系统,由主环CSRm和实验环CSRe构成,并以兰州重离子回旋加速器系统HIRFL作注入器。CSR将重离子束的能量从兆电子伏提高到千兆电子伏,同时利用空心电子束冷却技术将束流的动量分散及发射度降低1~2个数量级,并提供多种类的高电荷态重离子束以及放射性次级束(RIBs),以开展更高精度的物理实验及更广范围的应用研究。兰州冷却储存环于2006年建成并投入运行,实现了剥离注入与多圈注入、空心电子束对重离子束的冷却与累积、变谐波宽能区同步加速、等时性环型谱仪、RIBs的产生与收集以及重离子束的快慢引出,并实现了高能重离子束的空心电子束冷却,使得重离子束的动量分散降低到10^-5量级,而发射度收缩到0.1πmm•mrad以下。同时,完成了短寿命近滴线核素的高分辨质量测量物理实验及高能重离子束深层治癌的临床应用实验。