固支简支端部边界条件下同轴圆柱壳体的流致不稳定性研究

基于Paiedoussis等同轴圆柱壳体流致不稳定性的数学模型和研究方法，分析了固支－简支端部约束条件下同轴圆柱壳体系统的流致不稳定性，结果表明：同两端固支相比，固支－简支端部边界下壳体系统的失稳临界流速更低。     

An Approximate Calculation Method of Flux for Spherical and Cylindrical Sources with a Slab Shield

An approximate calculation method for unscattered flux from spherical and cylindrical sources with a slab shield is presented. The method is based on modifying the source geometry to a form convenient for calculation: The sphere is approximated by a conical fragment of spherical shell, and the cylinder by a columnar fragment of cylindrical shell. The procedure for manual calculation is relatively simple, and the difference between results of appoximate and exact calculations is less than +5% for large sources (μ ^s R⁰≦ 4), and±15% for small sources (μ_sR⁰≈0.25). Graphs of the functions for approximate calculation are presented. The method has several advantages over Rockwell's method.     

Numerical Solutions to Critical Problem of Reflected Cylindrical Reactor

The multi-region critical problem can be transformed into an eigenvalue problem in the classical sense by using the method of Kuscer & Corngold and of Wing. This transformation is applied to derive a variational formulation for a reflected reactor.

An approximate critical value of the multiplying factor is determined by maximizing the Rayleigh quotient for radially and totally reflected cylindrical reactors. It is shown that this approximate critical value is an upper bound of the true critical value.

From the facts that the operator is self-adjoint and the eigenfunction is positive, an expression is derived for the upper and lower bounds of the true eigenvalue, by making use of the approximate distribution. The difference of the upper and lower bounds is an uncertainty of the presumption of the true critical value. It is found that we can compute the bounds to any required precision.

The narrow bounds are calculated for two radially and one totally reflected cylindrical reactors.     

Analytical Solutions of Pressure Effects upon Current Transmission across a Diode

Space-charge limiting of current transmission can be neutralized by introducing gas into the diode. The relationship between gas pressure and transmitted current is determined by a combination of several basic physical processes. A model that can predict experimental observations over a wide range of pressures is utilized to show which processes dominate current transmission in various pressure ranges of interest. The quantitative analytical solutions of this model can be correlated with experimental results to yield effective values for secondary electron production, secondary electron drift velocity, electron range effects, and ionization avalanche. Figure 1 shows a typical diode geometry.     

Solutions of Diffusion Equations in Two-Dimensional Cylindrical Geometry by Series Expansions

Abstract

A solution of the multi-group multi-regional diffusion equation in two-dimensional cylindrical (p-z) geometry is obtained in the form of a regionwise double series composed of Bessel and trigonometrical functions.

The diffusion equation is multiplied by weighting functions, which satisfy the homogeneous part of the diffusion equation, and the products are integrated over the region for obtaining the equations to determine the fluxes and their normal derivatives at the region boundaries. Multiplying the diffusion equation by each function of the set used for the flux expansion, then integrating the products, the coefficients of the double series of the flux inside each region are calculated using the boundary values obtained above.

Since the convergence of the series thus obtained is slow especially near the region boundaries, a method for improving the convergence has been developed. The double series of the flux is separated into two parts. The normal derivative at the region boundary of the first part is zero, and that of the second part takes the value which is obtained in the first stage of this method. The second part is replaced by a continuous function, and the flux is represented by the sum of the continuous function and the double series.

A sample critical problem of a two-group two-region system is numerically studied. The results show that the present method yields very accurately the flux integrals in each region with only a small number of expansion terms.     

Effective Cadmium Cutoff Energies for Cylindrical Detectors with Cylindrical Filters

The effective cutoff energies for cylindrical detectors with cylindrical filters in isotropic neutron flux were studied. The reactor spectra used in calculating the effective cutoff energy were those for infinite homogeneous media using the free gas model of deuterium and carbon. The values of the effective cutoff energies for cylindrical geometry in isotropic neutron flux are intermediate between those in isotropic and beam neutron fluxes for slab geometry. Change of detector position in the filter considerably influences the value of the effective cutoff energy. The self-shielding effect is negligibly small in micro counters.     

Plasma Coaxial Discharge for Thin Film Deposition

A coaxial discharge, of 6 capacitors each with 7.71 μF, is used to explore plasma thin film coating by insert a graphite powder at the breach of the coaxial head. Plasma current sheath reached 25 kA, after 10 μs from the start of the discharge. The     

Relativistic atomic structure calculations for highly ionized atoms

Characteristics of the GRASP package for relativistic atomic structure calculations are outlined, together with applications to highly ionized atoms. Transitions with Δn = 0 in helium-like ions and in dielectronic satellites of interest in plasma diagnostics and solar flare spectra provide particularly successful examples of its use. More fundamental studies of atomic structure theory can be based on a numerical decomposition of the energy into terms proportional to different powers of α². The use of this approach in analysing recent experiments to test QED through measurement of the 1s2s ³S-1s2p ³P intervals in the helium isoelectronic sequence is discussed.     

Simplified Engineering Techniques for Predicting Diode Tree Responses

The feasibility of predicting equilibrium photocurrents in silicon switching diodes entirely from nondestructively measured electrical parameters is shown. The prediction method is derived from the basic theoretical equation for diode photocurrent. Junction areas and depletion widths are related to avalanche voltages and capacitance-voltage characteristics by a general solution to McKay's avalanche condition integral equation. Diffusion lengths are related to storage times. The feasibility of the prediction method is demonstrated by comparing predicted and measured values of equilibrium photocurrents in 46 test diodes.     

反应堆一维两流体模型二阶精度数值解法研究

探索一维两流体模型的二阶精度算法,并将其用于一阶精度程序TFIT,开发出二阶精度程序,采用flux limiter计算对流项,并采用表面张力加强数值解法的稳定性。通过对经典的不连续两流体冲击问题——water faucet问题进行模拟,得到冲击波在管内的前行过程,将二阶与一阶程序和精确解进行对比,结果表明:二阶精度的程序精度明显提高,其稳定性与一阶精度的程序保持一致,并能更好地捕捉管内冲击波。     

Miniature Coaxial Plasma Injector for Diagnostics by Beam Plasma Interaction

A miniature coaxial gun has been used to study the interaction between plasma beam and low density plasma formed in glow discharge. The peak discharge current flow between the coaxial electrodes was 5.25 kA as a single pulse with pulse width     

Relativistic radiationless transition probabilities for atomic K- and L-shells

Auger and Coster-Kronig transition probabilities have been calculated ab initio relativistically from perturbation theory, for frozen orbitals, in the Dirac-Hartree-Slater approach. Results in the j?j coupling scheme are tabulated for ≥22 elements with atomic numbers 18 ≤ Z ≤ 96.     

一维位置灵敏电阻阳极低能重离子探测器

本文讨论了微通道板电阻阳极低能重离子探测器的原理，给出了已研制成功的位敏电阻阳极离子探测器的结构和信号分析电子学线路。用￣（２３８）Ｐｕα放射源测量了位敏探测器在有效面积范围内的位置信号、位置线性和位置分辨。位置分辨好于０．３ｍｍ，已满足了离子原子碰撞的实验要求。     

EAST-ICRH系统高功率同轴隔直器的研制

EAST超导托卡马克是我国开展受控核聚变研究的新一代实验装置,离子回旋波加热(ICRH)是在该装置中加热等离子体的重要手段之一。离子回旋加热系统中的发射机和天线两者各有一个地电平,两个地电平会存在严重的相互干扰。高功率同轴隔直器的作用是用来隔断两者之间的直流通路,从而把两端的地电平分开,保证发射机和天线系统的正常运行。论文介绍了隔直器的原理、工程结构和设计指标,分析了S参数、端口驻波比的计算和仿真,最后给出了实际的隔直器参数曲线。     

Approximate Calculation Method for Second Order Sensitivity Coefficient

A simple method has been developed for calculating the second order sensitivity coefficient of static and burnup-dependent core performance parameters. The method is applied to a small and a large fast breeder reactors. Changes in core performance parameters due to 10% cross section changes are compared with that predicted by the first and the second order sensitivity analyses. Numerical results reveal that the changes in breeding ratio, reaction rate ratio of the ²³⁸U capture to the ²³⁹Pu fission rate and burnup reactivity loss due to the 10% change in the ²³⁹Pu fission cross section and/or the ²³⁹Pu v-value show nonlinear behavior, and the second order sensitivity can predict the changes accurately.     

One-Dimensional Vertical Electron Cyclotron Emission Imaging Diagnostic for HT-7 Tokamak

At the first stage of the electron cyclotron emission imaging （ECEI） diagnostic project on HT-7, a 16-channel vertical-resolved ECEI diagnostic has been developed and installed on HT-7 tokamak to measure electron cyclotron emission with a temporal resolution of 0.5 usec. The system works at a fixed frequency of 97.5 GHz. The sample volumes of the system are aligned vertically with a vertical channel spacing of 11 mm, and can be shifted across the plasma cross-section by varying the toroidal magnetic field. The high spatial resolution of the system is achieved by utilizing a low-cost linear mixer/receiver array and an optical imaging system. The focus location may be shifted horizontally when translating one of the optical imaging elements. The details of the system design and laboratory testing of the ECEI optics are presented together with the preliminary experimental results.     

正电子湮没一维角关联装置的探测器

正电子源为22Na,对能量为0.511MeV的正电子湮没辐射,我们用10×10×200BGO与Φ50×300NaI(Tl)在探测效率、能量分辨及温度性能等方面进行了比较。