用飞行时间法测量氚的深度分布

氚在材料中的浓度、深度分布及其在材料中的扩散行为,是从事核聚变研究者最为关心的问题之一。氚(钛)靶是14MeV中子发生器的主要部件,精确地分析氚在靶中的行为,可以为合理地设计氚靶的厚度提供依据,并使靶的寿命和密封的中子发生器的寿命得以延长。因此,研究一些可行的方法来分析氚在基质材料中的行为有着应用的价值。用离子背散射     

Measurement of fast-neutron flux density by means of156dY

V. G. Khlopin Radium Institute. Translated from Atomnaya Énergiya, Vol. 73, No. 6, pp. 504-405, December, 1992.     

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…     

An elgenvalue and eigenfunction study of time-dependent fast-neutron spectra in 232Th

The pulsed problem for fast neutrons in Th has been studied using the multigroup diffusion equation and eigenfunction expansion method. The time-dependent fast-neutron spectra have been obtained up to 8000 ns inside Th systems with buckling ranging from 0.0 to 0.015 cm⁻². The results have been obtained using the 27-group BARC data set. It has been shown that for a fast Th system, unlike a fast U system, all the time eigenvalues lie in the continuum and no discrete time eigenvalue exists. A fast Th system behaves more like a non-multiplying system. The spectra shift continuously to lower energies with increasing time. However, pseudo-asymptotic conditions are established in certain time intervals. The start of pseudo-equilibrium conditions and the duration for which they persist is seen to increase with decreasing buckling. The reason for the establishment of pseudo-equilibrium conditions has been discussed. The theoretical results for the instantaneous decay constant inside a 40 cm cube of Th have been compared with the experimental results of Moo et al. (1973). The present results are in good agreement with the above experimental results based on the ²³⁹Pu detector.     

The use of resonance detectors for the investigation of neutron spectra in fast-neutron reactors

The possibility of the investigation of the low energy portion of the neutron spectra in reflecting fast reactors by activated resonance detectors is considered.Absorber difference and 1/v absorption methods are illustrated by an example of the measurement of the flux distribution of resonance neutrons with energies of 4.9 ev (Au¹⁹⁷) and 2.95 kev (Na²³) in the reflecting reactors BR-1 and BR-5. It is shown that the neutron spectrum region from one to several thousand electron volts can be studied in adequate detail with the aid of the set of detectors described.The authors express deep thanks to A. I. Leipunskii for interest in the work and to I. I. Bondarenko and V. V. Orlov for helpful advice and comments.     

用飞行时间法测定回旋加速器束流能量

我所改建后的等时性回旋加速器,质子能量从10—30MeV连续可变。如何测定这些束流的能量,方法很多,如弹性、非弹性散射,核反应等。本工作用飞行时间法测定了该所等时性回旋加速器的束流能量。其优点是方法简单、可靠,测量结果准确度较高,在较宽的能量范围内都可以适用。     

多探测器快中子飞行时间谱仪

描述了一台串列加速器HI-13上的多探测器快中子飞行时间谱仪,并与国际上同类谱仪进行了比较。本谱仪主要用于能量大于8 MeV的快中子散射实验、次级中子双微分截面及带电粒子引起的出射中子能谱的测量。简要介绍了谱仪各主要部分(包括零信号拾取筒、氘气体靶、探测器、电子学等)的结构和特性及其在快中子实验中的应用。     

Study of space-dependent fast-neutron spectra and tritium breeding ratio in different assemblies of Li, Li and natural Li

Using diffusion theory and the eigenfunction expansion method, a detailed space-dependent study of fast neutron spectra has been carried out in ⁷Li, ⁶Li and natural Li assemblies of dimensions 100 × 60 × 60 cm³ and 30 × 60 × 60 cm³. Values of total (space-averaged) tritium breeding ratio (TBR) have been obtained for these assemblies. BARC-892, a 27-group data-set was used for these calculations.

The results of TBR for the smaller assembly have been compared with the corresponding experimental and calculated values of Takahashi et al. (1984). We find that the present values of TBR are in reasonably good agreement with the above experimental results.     

Comparison of lead-and sodium-cooled fast-neutron reactors

The author expounds his point of view concerning the comparative advantages and drawbacks of two types of technology for liquid-metal fast-neutron reators: lead and sodium. It is concluded that there are no substantiation and no significant factors justifying forced implementation of a lead-cooled reactor, especially in the existing economic climate in Russia. Successful advancement of a new reactor technoloy is possible at present only if the technology is accepted internationally and the principal nuclear countires participate. Russian Science Center “Kurchatov Institute”. Translated from Atomnaya énergiya, Vol. 86, No. 3, pp. 171–174, March, 1999.     

The development of a time of flight spectrometer for LARN

An elastic recoil detection time of flight system to depth profile light elements has been developed on ALTAÏS, the new Tandetron accelerator at LARN. The detector mounted at 45° from the beam axis consists of two isochronous electron detectors for the timing signal (START and STOP) and a 450 mm² heavy ion PIPS detector that detects the energy of the recoil atoms. The 2MV Tandem accelerator provides heavy ion beams with a maximum energy of 16 MeV depending on the charge transfer efficiency of the gas exchange canal located in the middle of the machine. A large variety of primary ion beams like ²⁸Si, ³⁵Cl, ⁶³Cu, ¹²⁷I or ¹⁹⁷Au can be produced with the SINIX heavy ion source and accelerated on the target. Typical current around 1 nA can be obtained. The energy transfer to the recoil atoms is typically in the MeV range and depends on the mass and the energy of the projectile. Some secondary effects like the energy loss in the carbon foils of the timing detector but also in the entrance window of the energy detector should not be neglected if we try to depth profile light elements with this technique. Time resolution of about 1 ns for the electrons detectors is suitable to obtain 1 amu mass resolution. Some examples of applications will be developed in this paper.