50MeV／u^12C离子实验靶区中子注量率的测量

用阈探测器中子活化法测量了50MeV/u~(12)C离子实验靶区出射的热中子以及E_n分别大于6、11、20、50MeV的中子注量率。     

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.     

Neutron dose equivalent rate for heavy ion bombardment

The fluence rate distribution of neutrons in the reactionsof 50MeV/u ^18O-ion on thick Be,Cu and Au targets have been measured with an activation method of threshold detectors andthe neutron dose equivalent rate distributions at 1m from the tqrgets in intermediate energy heavy ion target area are obtained by using the conversion factors from neutron fluence rate to neutron doseequivalent rate.     

无屏蔽条件下用25.4cm单球雷姆计测量中能重离子反应中子剂量当量的理论修正

用重离子反应出射中子能谱和角分布估算了用25.4cm单球雷姆计测量100MeV/u~(12)C+C和41.7MeV/u~(12)C+Fe两个重离子反应中子剂量当量时的理论修正系数。     

用阈探测器活化法测量50MeV/u重离子实验靶区的中子注量率、能谱和中子产额

用阈探测器中子活化法测量了50MeV/u ~(12)C离子实验靶区的次级中子平均注量率、角分布、粗略能谱,并估算了重离子反应的中子产额。     

重离子加速器实验靶区的中子剂量当量率

用阈探测器中子活化法测量了５０ＭｅＶ／ｕ＾１８Ｏ离子轰击Ｂｅ、Ｃｕ、Ａｕ厚靶出射中子的注量率分布,并利用中子注量率对剂量当量率的转移因子,得到了重离子实验靶区的中子剂量当量率分布。     

75MeV／u^16O离子在辐照生物实验区产生的中子角分布

应用Ａｌ为阈探测器对７５ＭｅＶ／ｕ＾１６Ｏ离子在辐照生物研究区产生的Ｅｎ〉６ＭｅＶ中子的角分布进行了实验测量，以了解辐照生物实验区的中子分布情况，为进一步开展的重离子冶癌研究提供辐射防护的实验数据。实验结果表明实验区产生的中子具有明显的前冲分布。     

Neutron yields and emission rates in the forward direction for 50MeV／u ^18O—ion on thick Be,Cu,Au targets

Total neutron yields and neutron emission rates in the forward direction for 50MeV/u ^18O-ion on thick Be,Cu,Au targets have been measured using an activation technique.The results indicate that neutron yields and emission rates in the forward direction depend on the atomic number of target nuclei,i.e.the lighter target the greater neurtron yield and neutron emission rate.Meanwhile,the neutron yield of ^18O-ion is greater than that of 12C-ion when target nucleus and incident energy per nucleon are identical.     

Experimental test of a new neutron threshold detector and its application

The Possibility of using 209Bi as a new threshold detector to measure high-energy neutrons was investigated for the first time.At the same time the experiment measured successfully the emitted neutron fluence rate,energy spectrum and dose equivalent rate distributions in the heavy ion target area using a detector complex including 209Bi,^115In,^27Al,^19Fand ^12C samples.     

Preliminary Experiments on Accelerator-Driven Subcritical Reactor with Pulsed Neutron Generator in Kyoto University Critical Assembly

A series of preliminary experiments on an accelerator-driven subcritical reactor (ADSR) with 14 MeV neutrons were conducted at Kyoto University Critical Assembly (KUCA) with the prospect of establishing a new neutron source for research. A critical assembly of a solid-moderated and -reflected core was combined with a Cockcroft-Walton-type accelerator. A neutron shield and a beam duct were installed in the reflector region for directing as large a number as possible of the high-energy 14MeV neutrons generated by deuteron-tritium (D-T) reactions to the fuel region, since the tritium target is located outside the core. And then, neutrons (14MeV) were injected into a subcritical system through a polyethylene reflector. The objectives of this paper are to investigate the neutron design accuracy of the ADSR with 14MeV neutrons and to examine experimentally the neutronic properties of the ADSR with 14MeV neutrons at KUCA. The reaction rate distribution and the neutron spectrum were measured by the foil activation method for investigating the neutronic properties of the ADSR with 14 MeV neutrons. The eigenvalue and fixed-source calculations were executed using a continuous-energy Monte Carlo calculation code MCNP-4C3 with ENDF/B-VI.2 for the subcriticality and the reaction rate distribution, respectively; the unfolding calculation was done using the SAND-II code coupled with JENDL Activation Cross Section File 96 for the neutron spectrum. The values of the calculated subcriticality and the reaction rate distribution were in good agreement with those of the experiments. The results of the experiments and the calculations demonstrated that the installation of the neutron shield and the beam duct was experimentally valid and that the MCNP-4C3 calculations were accurately carried out for analyzing the neutronic properties of the ADSR with 14MeV neutrons at KUCA.     

Neutron yields from 1 GeV/nucleon U ion beams on Fe target

Yields of neutrons produced by a ²³⁸U ion beam of 1 GeV/nucleon kinetic energy impinging on a thick Fe target were measured resulting in distributions differential in neutron angle (0° < _n < 20°) and in kinetic energy (T_n > 50 MeV). The data serve in radiation protection planning for next-generation rare-isotope beam facilities. The experimental data are contrasted with predictions from transport codes as currently used in radiation shield design studies.     

A mathematical method to calculate efficiency of BF3 detectors

In order to calculate absolute efficiency of the BF3 detector, MCNP/4C code is applied to calculate rela-tive efficiency of the BF3 detector first, and then absolute efficiency is figured out through mathematical techniques. Finally an energy response curve of the BF3 detector for 1~20 MeV neutrons is derived. It turns out that efficiency of BF3 detector are relatively uniform for 2~16 MeV neutrons.     

一种新阈探测器的实验验证和重离子靶区中子测量

验证了用^2099Bi作为一种新的阈探测器测量高能中子的可能性，并利用^115In,^27Al,^19F,^12C和^209Bi组成的阈探测器组合测量了中能重离子反应实验靶区出射中子的注量率分布、能量分布和剂量当量率分布。     

Measurements of neutron induced activation of concrete at 64.5 MeV

The present paper presents the measurement of neutron induced activations on concrete using the 64.5 MeV quasimonoenergetic neutrons produced at the intense ⁷Li(p, n) neutron source at Cyclotron and Radioisotope Center, Tohoku Univeristy (CYRIC). The data were corrected for the effect of continuous neutrons in the source. The neutron energy, neutron yields and the spectrum of continuous neutrons were confirmed with the neutron time-of-flight method and the neutron activation measurement of the ²⁰⁹Bi(n, Xn) reactions having various threshold energy values. The nuclides produced by thermalized source neutrons are negligible. New data were obtained for concrete activation.     

快中子活化法对声空化核效应的验证

采用纯铜作为阈探测器检测声致核聚变产生的14 MeV中子。根据14 MeV中子与Cu的核反应,选择合适的放射性核素及其特征γ峰作为测量依据。中子辐照时间为50 min,经30 min和198 min冷却,NaI探测器分别测量了超声和非超声下活化铜片的511 keV特征γ峰计数,测量结果显示,采用短冷却时间可测得⁶²Cu的511 keV γ特征峰,γ峰净面积计数增量ΔC均为正值,具有统计意义,在声空化条件下核反应液体中D-T反应产生的14 MeV中子发生率大于在非声空化条件下的;采用长冷却时间可测得⁶⁴Cu的511 keV γ特征峰,ΔC均为正值,具有统计意义,在声空化条件下核反应液体中D-D反应产生的2.45 MeV中子发生率大于在非声空化条件下的。由此验证了声空化核效应（NEAC）,并初步分析了中子成核声空化核效应的机制。     

Anisotropy of Scintillation Response of Anthracene to Neutron Generated Recoil Protons and Carbon Ions

The directional anisotropy in the scintillation response of an anthracene crystal to heavy charged particles was investigated. Energetic carbon and hydrogen ions were produced internally by scattering fast neutrons from the constituent nuclei. By use of a two detector coincidence system, the scintillations due to monoenergetic ions recoiling in a particular direction were selected and analyzed. The energies of the ions ranged from 2 to 3.5 MeV for the carbon recoils and from .9 to 7.3 MeV for the hydrogen recoils. Even though there was a wide variation in the average specific energy loss of the heavy charged particles considered, the magnitude of the anisotropy only varied between 39% for the carbon recoils and 20% for the 7.3 MeV hydrogen recoils. The measured hydrogen ion response in a particular direction as a function of energy was found to be approximately described by the formula suggested by Birks, dL/dE = (1 + kBdE/dx)-1, with kB being directionally dependent. The directional carbon ion response appeared to be a linear function of energy over the energy range investigated.     

^92Mo（n,p）^92Nb^m反应截面的测量和低能中子的扣除

用活化法相对标准反应测量了＾９２Ｍｏ（ｎ,ｐ）＾９１２Ｎｂ＾ｍ反应截面,其能区为５－１９ＭｅＶ。测量中分析了低能中子的影响,采用恰当的方法有效地扣除他们的干扰。特别是在１７－１９ＭｅＶ能区,用空靶扣除了Ｄ－ｄ低能中子的影响,得到了合理的截面走向。     

Systematic investigation of spectroscopic factors from (d,p) reactions for deuteron nuclear data evaluation

Spectroscopic factors for the (d,p) reactions on ¹²C, ²⁷Al, ⁴⁰Ca, and ⁵⁸Ni for incident deuteron energies up to 100 MeV were extracted systematically by fitting theoretical distorted wave Born approximation calculations to the existing experimental data. The extracted spectroscopic factors show similar incident energy dependence for all the target nuclei. An empirical expression describing the energy dependence has been deduced and implemented in a computational code system developed specially for deuteron-induced reactions. The calculation with the code system reproduces the measured ²⁷Al(d,p)²⁸Al cross sections in the incident energy range from the threshold to 20 MeV and the measured double-differential cross sections for (d,xp) reactions on ¹²C and ⁵⁸Ni at 56 and 100 MeV fairly well.     

Theoretical and Experimental Determinations of Neutron Energy Deposition in Silicon

Theoretical calculations have been made of the energy deposited in silicon in ionization and elastic interactions by neutrons in the energy range of 60 keV to 15 MeV. In contrast to earlier determinations, care was taken to calculate accurately the effects of atomic recoils. These are of primary importance for permanent effects in silicon at all neutron energies and account for about 30% of the transient ionization at 14 MeV. To test the calculation of the energy deposited by 14 MeV neutrons, experiments were performed with a pulsed d-t generator. The experimental values in rads per unit fluence were (11 ± 2) × 10-10 rad-cm2 for special p-n junctions and (8 ± 2) × 10-10 rad-cm2 for power transistors. Both experimental values agree, withi jerror, with the calculated value of (8 ± 1) × 10-10 rad-cm2. The calculated variation of radiation damage in silicon with neutron energy was compared with existing experimental data. There is general agreement of theory with experiment from 200 keV to 14 MeV.     

Evaluation of Neutron- and Proton-induced Nuclear Data on 27Al up to 2 GeV

We have evaluated neutron and proton nuclear data of ²⁷ Al for energies up to 2 GeV. The best set of optical model parameters were obtained from 20MeV for neutrons and from reaction threshold for protons up to 250 MeV with the phenomenological non-relativistic potential forms incorporating effects of the dispersion relationship and results of the Dirac phenomenology. The transmission coefficients for neutrons and protons derived from the optical models were fed into the GNASH code system to calculate angle-energy correlated emission spectra for light ejectiles and gamma rays. For energies between 250 MeV and 2 GeV, the total, reaction and elastic scattering cross sections were evaluated by an empirical fit and recent systematics. Emitted nucleon and pion spectra were estimated by use of QMD+SDM (Quantum Molecular Dynamics+Statistical Decay Model).