Single Wire-Plate Alpha Particle Counter Characteristics in Air

Spark and oorona-streamer characteristics have been obtained for a wire-plate alpha particle counter having an electrode gap 1.27mm - 12.7mm and a wire diameter 0.07mm - 0.5mm. Applied voltages Va up to 22kV were employed. The working characteristics for different quenching resistances R are reduced to a single fundamental characteristic independent of R. Conditions are given for attaining a flat counting characteristic plateau in both the sparking mode and coronastreamer mode of operation.     

Fading Characteristics of Alpha Radiation Signals Stored in an Imaging Plate

For the quantitative measurement of alpha radiation using the technique of imaging plate (IP), the fading characteristics of both the gross photostimulated luminescence (PSL) values and the counts of alpha spots in the IP irradiated with an ²⁴¹Am source were experimentally studied at different temperatures and elapsed times. Based on the experimental data and the proposed theory, the functions of fading correction were established by fitting the data by the least-square method and testified. The results showed that the fading correction was important and the functions were practical for more accurate measurements of alpha radiation. Compared with the traditional PSL method, the spot counting method was preferable for a more accurate measurement of alpha radiation.     

Observation of Alpha Particle Effects in the Charge-Coupled Image Sensor

Alpha particle effects in the charge-coupled (CCD) image sensor were evaluated by using Am-241, Th, and Po-210 radiation sources. Soft error rate due to alpha particle hit was dependent upon alpha energy spectrum and on integration time and photogate bias of the device. The device was operated at frequencies between 200 kHz and 1 MHz during the irradiation and was found to have no effect on the soft error rate. A charge collection efficiency of 64% was observed as the device was exposed to a 4.2-MeV alpha. Material-asssociated characteristics such as diffusion length and lifetime of the minority carrier were calculated from the outcome of the charge collection efficiency. More than two orders of magnitude in increase of dark signal and charge transfer loss were observed as the device was subjected to a total radiation exposure of 105 rads (Si). The device degradation is due mainly to the threshold voltage shift and lattice defects.     

Upset Events in Josephson Digital Devices under Alpha Particle Irradiation

Preliminary results on the effects of 5 MeV alpha particle irradiation on the electrical characteristics of large area (approximately 60 ?m2) Josephson Nb-amorphous Si-Nb tunnel devices indicate that these particles are effective in producing upset events when the device is operated in a switching mode. For bias currents very close to the critical current, IC, upset rates are near 0.1 per alpha. At a reduced bias current of 0.65 IC the upset rate is decreased but is still finite (0.002 per alpha). In addition, an hysteretic effect was observed for the critical current of the device under alpha irradiation. A simple heating model does not appear adequate to explain the observed upset rate as a function of bias current and the hysteretic effect.     

L-Shell Ionization in Proton and Alpha Particle Collisions with Argon

We report results of coupled-state calculations of argon L-shell ionization by proton and alpha particle collisions in the 100 to 500 kev/amu energy range. Our target-centered basis includes up through f-states. We have explored the angular momentum convergence and ability of our pseudostates to describe the ionization continuum by comparing to the Born calculations of Choi; excellent agreement is obtained. In the Born we have shown the effect of using different independent-particle target potentials; these effects are large, particularly at low energy. We propose a modification of the Hartree-Fock potential that leaves all the wavefunctions and the bound orbital energies unaltered, but that lowers the continuum by an amount that brings the L-shell ionization potentials roughly into agreement with experiment. Our coupled-states calculations show deviations from the 1st Born approximation, and are in fair agreement with experiment. A complete comparison to experiment will require the calculation of the charge transfer channel contribution to the vacancy production.     

Ladu计数器性能研究

测量了角响应、径向微分响应、能量响应及球腔内中子计数率分布,并估算了有效中心。角响应小于5%,径向微分响应与实心球探测器的情况相同。在源距大于5倍计数器半径的情况下,忽略有效中心与几何中心之差异所导入的响应值误差小于0.7％。球腔内超热与热中子计数比小于10％,计数率依赖于热中子探测器所在位置。大约在200eV至5MeV能区,能量响应是平伸的,误差小于±18％。     

测量空气中Rn,Tn子体的α谱法

本文介绍了测量空气中Rn、Tn子体浓度的α谱法,给出相对标准偏差的计算公式及计算机程序框图,讨论了此方法的固有不确定性及其影响因素,给出最佳实验条件。     

Development of LIPS Prototype to Monitor Trace Element of Particle Mater in Air Aerosols

正The laser induced plasma spectroscopy(LIPS)has a potential application to detect trace element from environmental medium without sampling and pretreatments.The prototype of enhanced LIPS has been set up to demonstrate     

Characteristics of Counter current Gas-Liquid Two-Phase Flow in Vertical Tubes

Investigations into the flow pattern and the void fraction for countercurrent air-water flow in vertical tubes of diameter D = 40 and 80 mm were reported. The flow maps were presented and showed slug flow regime occupied larger portion on them. The void fraction was measured by the quick-closing valve technique, in bubbly and slug flow regime.

The void fraction data available in the literatures as well as present work for counter- current flow in vertical tubes were correlated in terms of dimensionless groups. The experimental results of the present work were also compared with the drift flux model.     

CE-3有效载荷APXS可靠性预计及评估

粒子激发X射线谱仪(APXS)是以元素成分鉴别和定量分析为目标的CE-3巡视器有效载荷。该工作针对APXS电子学系统建立了可靠性模型,并进行了可靠性预计。通过对APXS可靠性预计计算的可靠度与给定的可靠度进行对比,发现设计中的薄弱环节。对APXS电子学系统进行老化试验,用阿伦尼乌斯(ARRHENISUS)反应模型获得了工作温度下的寿命因子,利用贝叶斯法点估计和区间估计对试验的结果进行了可靠性评估,并对影响结果的主要因素进行讨论,提出APXS研制阶段的各项可靠性要求。     

Measurement of Dead Zone Characteristics of Gas Counter with Gamma-Ray

An evaluation method with uncollimated γ-rays has been proposed for the dead zone of gas counters without entrance windows. The obtained dead zone characteristics for the proportional, SQS and GM modes are almost consistent with those obtained with β-rays. Some difference in the dead zones obtained with γ-rays and β-rays has been discussed. This new method is effective to confirm and improve the operation mode of counters.     

The Luminescence Decay Time of Air and Nitrogen-Oxygen Mixtures Excited by Alpha Particles

A systematic study of nitrogen luminescence decay time has been performed, exciting nitrogen by ? particles in various oxygen mixtures and air near atmospheric pressure. Results obtained by varying the oxygen ratio from 0 to 20% and total pressure from 200 to 2000 torr are given and explained by kinetic theory of the phenomena. It seems that a resonance collision process is responsible for the changes in the decay times of the second positive nitrogen group. An extrapolation of the measurements gives a decay time of 0.52 ns for air at atmospheric pressure. We proposed to study the luminescence decay time of air excited by the alpha particles of Polonium 210, in a pressure range between 200 and 2000 torr. As is known, nitrogen is mainly responsible for the luminescence of air irrespective of the excitation method; the most intense bands emitted correspond to transitions of the second positive system of the N2 molecule arn the first negative system of the once ionised molecule N2+5. Between 220 and 600 nm, the spectral domain of our experiments, the presence of oxygen is shown by a strong inhibition of the intensity of the nitrogen bands and by the appearance of the auroral line OI at 557.7 nm line, whose intensity is always very small. We therefore compared the luminescence decay time of the air and that of a mixture containing 80% nitrogen and 20% oxygen.     

基于ANSYS/LS-DYNA的抗飞机撞击结构非线性动力分析

APC壳是核电站抵御飞机撞击的主要屏障,本文运用非线性有限元程序LS-DYNA对某核电站燃料厂房APC壳进行了分离式建模,并对大型商用飞机的撞击进行了数值计算,对APC壳的动力响应及弹塑性特性进行了研究分析,提出了大型商用飞机撞击局部效应的观点,为APC壳的设计计算提供参考。     

空气中吊蓝结构的振动特性分析

由于反应堆吊蓝结构复杂,采用有限元法对其进行动力分析时,很难直接对结构的所有细节都作真实模拟。为此,根据吊蓝结构及动力分析的特点,对吊蓝结构的支承边界条件和局部复杂结构作了必要的简化,建立了两类简化模型。同时,计算了两个试验模型的振动特性。经对计算频率值与试验实测频率值的比较表明：本吊蓝支承边界条件及局部结构的简化方法是合理、可行的。     

Symplectic Simulation of Fast Alpha Particle Radial Transport in Tokamaks in the Presence of TF Ripples and a Neoclassical Tearing Mode

A Hamiltonian guiding centre drift orbit code based on a symplectic integration algorithm, which enables the efficient calculation of particle trajectories and diffusion coefficients, is applied to fast alpha particle motion in magnetically perturbed tokamak plasmas. In particular, fast ion drift motion is examined in the presence of a stationary, low mode-number MHD magnetic perturbation in a toroidally rippled tokamak with circular flux surface. The main focus of our study is to investigate the dependence of the radial diffusion coefficient of energetic ions on their energy, on the perturbation strength and the localization of the perturbation. As expected, the resonance between bounce motion and toroidal field ripples plays a significant role in this context. For an ensemble of fast ions uniformly distributed in toroidal angle but with a given poloidal starting position their radial transport coefficient takes on higher values in the neighbourhood of resonance speeds and can exhibit there local minima, i.e. it shows an M-shaped speed dependence around resonances for sufficiently strong ripple perturbations. Expectedly, the addition of a modelled low-mode number neoclassical tearing mode perturbation will modify the pure ripple resonance structure of the radial diffusion coefficient. Depending on the strength and localization of the MHD mode it can cause enhancement or degradation of the radial ripple diffusion coefficient.     

竖直矩形窄缝通道内单个蒸汽泡和空气泡尾流特性的对比

采用粒子图像测速仪(PIV)对绝热条件下单个蒸汽泡在矩形窄缝通道内去离子水中上升的尾流特性进行研究,分析了入口平均流速和汽泡直径对蒸汽泡最终上升速度、尾流结构以及尾流速度场的影响,并与单个空气泡进行对比。实验结果表明,绝热条件下蒸汽泡的最终上升速度与汽泡直径的对应关系和空气泡存在差异,蒸汽泡尺寸和入口平均流速对蒸汽泡尾流的影响以及尾流中最大纵向速度发生的位置与空气泡相似,无显著差异。     

α粒子间接探测技术原理简介

介绍了一种α粒子间接探测技术原理,解决某些场合直接测量α粒子的难题。α粒子在空气中产生的离子数与α粒子的注量和能量之积成正比,通过收集α粒子在空气中产生的电离离子的方法,来间接测量α粒子,根据所测电离电流估算α核素的活度。根据测量原理,设计制作了一套间接测量α粒子的实验装置,并进行了实验验证。结论表明间接α测量技术原理可行,测量结果可靠,对α粒子有较好的响应。     

Particle flux in an annular gap about a sphere

We develop a method for joining diffusion theory to a void region in a consistent manner. In particular, we apply the theory to a three region problem with a central solid core, surrounded by a concentric void shell and this in turn is surrounded by a concentric shell of another solid material. The sources can be either incident on the outer surface or uniformly distributed in the inner and outer regions. The void flux is calculated from the free streaming Boltzmann equation and is linked to the diffusion equations by assuming that the angular distribution on the surfaces follows the form A + B cosϑ, where A and B are related to the diffusion theory fluxes in the inner and outer regions. This procedure allows us to calculate the flux throughout the solid and void regions without making any diffusion theory assumptions in the void. Numerical results are given to illustrate the method and comparisons with exact transport calculations are given to establish the accuracy. An extension of the method to deal with axially symmetric systems is also given in Appendix B. The theory will apply to neutrons and photons.