Electrical Properties of Uranium Carbonitride

Rapid separation using NTA in paper electromigration was applied to the study of the γ-decay of ¹⁴⁸Pr and ¹⁴⁹Pr produced in the fission of ²³⁵U. The γ-ray spectrum was measured with a high-resolution Ge(Li) detector. The γ-transitions found to decay with half-lives shorter than 3 min were: 135, 162, 256, 300, 511, 614, 696, 868, 1,022 and 1,248 keV. Of these, the values of 300 keV, and of 135 and 162 keV were in fair agreement with those reported for ¹⁴⁸Pr and ¹⁴⁹Pr. The decay plot of the strong photopeak of 300 keV presented good linearity and the accurate half-life of ¹⁴⁸Pr could be determined as 2.30±0.03 min, which is longer than the 1.98 min reported for ¹⁴⁸Pr. Similar decay plots of both photopeaks at 135 and 162 keV gave a half-life of 2.9±0.1 min for ¹⁴⁹Pr, which again is longer than the reported value of 2.3 min. Other low intensity photopeaks at 256, 696, 868 and 1,022 keV decaying with half-lives of 2.1～2.4 min can possibly be attributed to ¹⁴⁸Pr. The γ-transitions of 110, 578 and 742 keV reported for ¹⁴⁹Pr could not be observed in this experiment.     

Electrical Properties of Neutron-Irradiated Silicon at 76°K: Hall Effect and Electrical Conductivtty

Defects produced in p-type silicon by neutron irradiation have been investigated using electrical conductivity and Hall effect measurements at 76°K. Samples from crucible-grown (1, 10, and 50 ohm-cm) and float-zone (10 ohm-cm) boron-doped silicon were irradiated at 76°K with nearly fission spectrum neutrons and annealed isochronally between 76° and 700°K. The electrical properties of neutron-irradiated p-type silicon exhibit an illumination dependence similar to that observed previously in n-type silicon and attributed to the presence of defect clusters. Therefore, neutron-produced changes in the electrical properties of p-type silicon also are attributed to defect clusters. The sensitivity to illumination was observed for all resistivities and for both crucible and float-zone p-type silicon. The illumination-induced conductivity decays slowly with time at 76°K and influences the thermally produced changes in the electrical properties upon annealing for temperatures up to 150°K. Neutron-produced changes in the electrical properties measured after annealing to 150° K are found to be qualitatively consistent with an insulating void model for cluster-space-charge regions. The best modeling of the experimentally observed changes is for the 50 ohm-cm (large void volume) silicon. The annealing loss of the light sensitive defects occurs in diffuse stages between 150° and 550°K with the largest stage between 150° and 240°K. A major fraction of the hole mobility annealing parallels that for the light sensitive defects and suggests that the mobility change is caused primarily by defect clusters.     

Electrical Properties of Plasma Deposited Low-Dielectric-Constant Fluorinated Amorphous Carbon Films

Fluorinated amorphous carbon （a-C：F） films were deposited at room temperature using C4Fs and CH4 as precursor gases by electron cyclotron resonance chemical vapour deposition （ECR-CVD）. Chemical structures were analysed using X-ray photoelectron spectroscopy （XPS）. The current conduction shows ohmic behaviour and the leakage current increases with the content of C sp2 in the deposited a-C：F films at a low electric field. The behaviour of the leakage current is well e~plained by the Poole-Frankel mechanism at a high electric field. The interface traps, rather than chemical structures, of a-C：F films determine the PF emission current.     

Laser-induced optical reflection and absorption of GaP

Changes in the optical absorption and reflection coefficients of GaP induced by irradiation with 600 ns laser pulses of the wavelenghts at the direct and indirect band gaps have been measured. It is found that a persistent increase in the absorption coefficient and a permanent decrease in the reflection coefficient, in addition to transient increases in the absorption and reflection coefficients, are induced, by irradiation at the band gap. The persistent component is found to be evolved with a surprisingly long time constant of about 10 ms. This component is ascribed to laser-induced modification of the surface layers or damage formation. The transient component is ascribed to temperature rise on the basis of time-resolved optical absorption measurements. It is found that the persistent changes are induced by irradiation with the indirect band gap photons at a fluence which induces only a little change in the transient reflectivity. The threshold laser fluence to create the surface modification by the indirect band-gap irradiation is found to be only four times that by direct band-gap irradiation. A delayed reflectivity change is found to be induced by irradiation at the indirect band gap and is ascribed to the modification of surface layers by photons at the surface layer, which enhances the absorption coefficient. We interpret these experimental results in terms of non-thermal laser-induced atomic processes.     

Effect of Low Temperature Electron-Irradiation on the Electrical Properties of Undoped GaSb

Undoped GaSb samples were irradiated at 15°K and 80°K with 0.5 MeV and 1.0 MeV electrons. The effects of the irradiation on the temperature dependence of the Hall coefficient RH and the Hall mobility ?H were investigated and a study of the recovery of the radiation-produced changes of these properties was made. After irradiation the Hall coefficient curves in a log RH vs T-1 diagram exhibit a maximum at low temperatures which indicates impurity conduction resulting from radiation-produced defects. At higher temperatures where the normal conduction mechanism is predominant the sign and magnitude of the radiation-produced changes of the Hall coefficient depend in a complex manner on measurement temperature, irradiation dose and irradiation energy. The Hall coefficient data obtained after small irradiation doses provide evidence that both acceptors and donors are produced by the irradiation. Donor production appears to be more pronounced at 1.0 MeV than at 0.5 MeV. At low temperatures the reciprocal Hall mobility has a tendency to vary stronger than linear with increasing irradiation dose. The dependence of the change of the reciprocal Hall mobility on the measurement temperature indicates that a substantial fraction of the radiation-produced defects act as neutral scattering centers. Recovery between 15 and 390°K occurs in four major stages which are located near 124, 168, 210 and 360°K. Acceptors are removed in all four stages. Evidence for the removal of donors is found only for stage IV.     

Recent Developments in GaP(Cs)-Dynode Photomultipliers

Recent developments in GaP(Cs)-dynode photomultipliers are reviewed. The physics of secondary emission is discussed and models are described which explain secondary emission from conventional dynode materials and from GaP(Cs) dynodes. The concept of negative electron affinity is explained in terms of an energy diagram. Device performance is reported with regard to both electron and time resolution. A general discussion of the characteristics of GaP(Cs)-dynode photomultipliers is included.     

Atomic-scale structure of irradiated GaN compared to amorphised GaP and GaAs

We have compared the atomic-scale structure of ion irradiated GaN to that of amorphised GaP and GaAs. While continuous and homogenous amorphised layers were easily achieved in GaP and GaAs, ion irradiation of GaN yielded both structural and chemical inhomogeneities. Transmission electron microscopy revealed GaN crystallites and N₂ bubbles were interspersed within an amorphous GaN matrix. The crystallite orientation was random relative to the unirradiated epitaxial structure, suggesting their formation was irradiation-induced, while the crystallite fraction was approximately constant for all ion fluences beyond the amorphisation threshold, consistent with a balance between amorphisation and recrystallisation processes. Extended X-ray absorption fine structure measurements at the Ga K-edge showed short-range order was retained in the amorphous phase for all three binary compounds. For ion irradiated GaN, the stoichiometric imbalance due to N₂ bubble formation was not accommodated by Ga–Ga bonding in the amorphous phase or precipitation of metallic Ga but instead by a greater reduction in Ga coordination number.     

Recent Work on Fast Photomultipliers Utilizing GaP(Cs) Dynodes

There exists an increasing demand for photomultipliers with better time resolution, higher count rate capabilities and generally faster time response. This paper discusses fundamental electron-optical considerations which determine the speed of response of electrostatically-focussed photomultipliers. The nature of time broadening is discussed with regard to geometrical and initial velocity effects at dynode surfaces. Time limitations inherent in the dynode material itself are also treated. Examples of different fast photomultiplier structures are given. A discussion of various delta-function light sources is included and the relative merits of these sources with respect to time performance, ease of use and cost is reviewed.     

Radiation Response of Fiber Optic Waveguides in the 0.4 to 1.7? Region

The response of fiber optic waveguides to ionizing radiation has been studied. Measurements of the growth and decay of the radiation-induced loss at 0.82? have revealed that fibers with low OH are more susceptible to damage than those with high OH. The addition of P to Ge-doped silica core fibers has been found to suppress an intense transient absorption. Spectral measurements of the radiation-induced absorption between 0.4 - 1.7? have shown an increase in the OH overtone and combination band intensity with irradiation so that the induced loss at 1.3? is actually less in the low OH content silica core fibers than in the high OH content fibers. Real time spectral measurements of the damage following a pulsed irradiation have lead to an identification of the absorption bands and damage mechanisms responsible for the radiation-induced absorption.     

氢化锆-水-铀栅格特性研究

本文的目的在于研究氢化锆在增殖系统中的慢化特性,在N_h/N_5为233—543范围内做了七个临界实验,在N_H/N_5=233,337两个准均匀栅格上做了热谱、通量分布、温度系数、瞬发中子衰减常数、材料的反应性系数等测量。七个临界实验、两个准均匀栅格的热谱与反射层节省等测量结果均与理论计算结果相符合,计算中用的是一维四群扩散理论,氢化锆介质的散射核是用晶格结构的声子谱模型获得的,从而说明这个计算模型是可用的。     

Structure Design and Test Research on the Electrical Properties of High Voltage Instrumentation Cables for the Fusion Reactor

The HV instrumentation cable is an important route for the signals transmission from the superconducting magnets to the control system, it should be long term operated at around 4.2 K and withstand the high voltage over several dozens of kilo volts during the failure operational contrition, meanwhile the cable should be flexible enough to assemble and arrange to the magnet system. According to the instrumentation cable technical requirement, one new type instrumentation cable was designed, after the electrical properties under high voltage were verified in ASIPP lab, the new type instrumentation cables fully meet the technical requirement.     

1.7MeV电子辐照对TiNi形状记忆合金相变温度的影响

用能量为１．７ＭｅＶ不同注量的电子辐照了ＴｉＮｉ形状记忆合金,通过温度控制使辐照在合金马氏体相进行,发现辐照使合金的马氏体逆相变开始温度Ａｓ和结束温度Ａｆ降低,且Ａｆ对电子辐照更敏感,相变温度滞后宽度减小;马氏体相变开始温度Ｍｓ和结束温度Ｍｆ基于无变化。ＸＲＤ结果表明电子辐照造成了马氏体相点阵畸变,随辐照注量的增加有增大的趋势,并且较大注量的晶面间距都增大。说明辐照引入的点缺陷增加了马氏体弹性应变     

Electrical simulation of nuclear reactors

The application of electrical simulation methods to nuclear reactor calculations considerably shortens the time required for the computational work. In this review the advantages and disadvantages of simulators are discussed and an example is given of the simulation of the reactor isotopic composition with the help of the simulator MN-7. The effectiveness of the electrical simulation method for the investigation of non-stationary reactor processes is shown by an example of design calculations carried out for an automatic power regulator for a reactor. It is shown that it is possible to simulate nonstationary processes occurring in a power reactor, taking into account the temperature coefficients of the reactivity; other applications of simulators in reactor design are indicated.     

用核噪声方法测量氢化锆零功率堆的瞬发中子衰减常数

瞬发中子衰减常数α是反应堆的重要动态参数,由次临界和临界状态下的瞬发中子衰减常数可以刻度出反应堆的次临界深度。在瞬发中子衰减常数的测量中,脉冲中子源方法是经常使用的非常成熟的方法。本文叙述另一种方法——核噪声方法测量瞬发中子衰减常数,这种方法使用中子探测器,探测堆内中子水平的涨落,通过对中子涨落信号的分析处理,导出瞬发中子衰减常数α。与脉冲中子源方法相比,核噪声方法的优点是测量方法简单,只需在反射层内放置中     

85MeV^19F离子辐照GaP的正电子湮没研究

用正电子湮没寿命技术研究了2.4×10     

85MeV~(19)F离子辐照GaP的正电子湮没研究

用正电子湮没寿命技术研究了 2 .4× 10 15 cm2 和 2 .2× 10 16 cm2 85MeV19F离子辐照GaP的辐照效应。结果表明 ,辐照在GaP中产生浓度较高的单空位 ,且随辐照剂量增大浓度增加