The Effects of Neutron Radiation on Second Breakdown and Thermal Behavior of Silicon Transistors

A method of measuring and the subsequent analysis of this data has indicated that the "thermal time constant" of silicon diffused transistors decreases with increasing neutron dosage. Emperically, it was noted that thermal time constant degradation constants, K?, can be assigned to all devices examined. For the silicon planar devices studied, degradation constants varied from 2.6 × 10-13cm2/neut for the radiation resistant devices, to 1.4 × 10-12 cm2/neut for other devices examined. By examining previous data for single diffused transistors the thermal time constant degradation factor was 2 × 10-11 cm2/neut. The conclusion of this report is that the "thermal time constant, which is related to second breakdown, effectively degrades upon exposure to neutron radiation, thereby decreasing the safe operating area of the device. However, the extent of degradation per dose may be predictable by data presented in the text.     

用热中子照相法检测火箭导爆索

介绍了清华大学研究院反应堆水平孔道上的一个中子照相系统,通过理论分析和实验测定评价了它的中子照相能力,并对火箭导爆索进行了成功的检验。     

Second Breakdown and Damage in 1N4148 from Oscillating Electrical Transients

The conditions for initiating second breakdown in 1N4148 diodes were investigated with reverse-biasing square pulses following high forward injection (prestress). It was found that at a certain prestress the reverse voltage necessary for inducing second breakdown suddenly drops from the normal reverse breakdown voltage to about 20 percent of this value. At higher prestress the power necessary for junction damage from the reverse pulse is higher by more than an order of magnitude than without prestress, and no transition to second breakdown is observed. These results are not in agreement with present models of second breakdown and junction damage.     

反应堆压力容器辐照监督无损评估技术研究

反应堆压力容器（RPV）的辐照脆化问题是核安全的重中之重,影响到核电厂的安全性、经济性与公众信心。介绍了传统RPV辐照监督方案,讨论了现行技术的局限性,梳理了RPV辐照监督无损评估技术国外研究进展与存在问题,在实验与理论研究的基础上创新性地提出了中子辐照条件下RPV钢力学性能预测统一模型,并形成了基于电磁性能的RPV辐照监督无损评估技术,进一步完善后具有较好的工程应用前景。同时指出了开展RPV钢电磁性能实验研究,既有助于从一个全新的角度理解与再认识国产RPV钢长寿期服役时的辐照脆化行为,又有利于揭示RPV钢辐照脆化机理,丰富辐照脆化的基础理论。      

Electrothermal Breakdown Mechanisms for Multilayer Insulation

The problem of the electrothermal breakdown of thin bilayer dielectric insulation used in nuclear-power systems is examined. Analytical expressions relating the parameters at the breakdown boundary are obtained for certain limiting cases. It is shown that the best electric strength qualities are obtained at the same current density in both layers of insulation in the most highly stressed section when several distributed sources of e.m.f. are present. These conditions can be obtained by adjusting the resistances of the layers or using auxiliary shunts, including short-circuiting in one of the layers.     

核燃料元件三维中子成像定量无损检测方法研究

中子照相是无损检测技术(NDT)中的一种。可用于检测核燃料元件内部缺陷、确定燃料芯块中~(235)U富集度、检测燃料内可燃毒物、确定包壳氢聚的位置及含量等。传统的核燃料元件中子照相方法获得二维检测成像,无法获得芯块碎片形貌、芯块内部颗粒分布、包壳破损状态等缺陷的三维立体形态信息。本文介绍在中国先进研究堆(CARR)及德国亥姆霍兹柏林研究中心(HZB)开展的核燃料元件三维中子成像定量NDT方法研究。缺陷的三维定量可获得内部杂质的三维成像,并可定量测量相关参数。包壳氢聚的三维测量可实现几乎所有包壳位置的氢聚含量定量测量。     

Experimental Study on Electrical Breakdown for Devices with Micrometer Gaps

The understanding of electrical breakdown in atmospheric air across micrometer gaps is critically important for the insulation design of micro ＆ nano electronic devices. In this paper, planar aluminum electrodes with gaps ranging from 2μm to 40 #m were fabricated by microelectromechanical system technology. The influence factors including gap width and surface dielectric states were experimentally investigated using the home-built test and measurement system. Results showed that for SiO2 layers the current sustained at 2-3 nA during most of the pre-breakdown period, and then rose rapidly to 10-30 nA just before breakdown due to field electron emission, followed by the breakdown. The breakdown voltage curves demonstrated three stages： （1） a constantly decreasing region （the gap width d 〈5 μm）, where the field emission effect played an important role just near breakdown, supplying enough initial electrons for the breakdown process; （2） a plateau region with a near constant breakdown potential （5 μm〈 d 〈10 μm）; （3） a region for large gaps that adhered to Paschen＇s curve （d 〉10μm）. And the surface dielectric states including the surface resistivity and secondary electron yield were verified to be related to the propagation of discharge due to the interaction between initial electrons and dielectrics.     

A Rising Force for the World-Wide Development of Laser-Induced Breakdown Spectroscopy

<正>Laser-induced breakdown spectroscopy(LIBS)has attracted many academic and industrial interests world-wide due to its unique advantages,such as little or no sample preparation requirement,in-situ/online and multi-elemental analysis,and remote sensing etc.,and it has been regarded as a"future super star"     

EAST全超导托卡马克等离子体击穿模拟

托卡马克装置的等离子体击穿有两个关键因素：合适的环电压和真空区域尽可能大的零场区。极向场线圈电流放电引起真空室感应涡流的产生,感应涡流对零场的优化、环电压的建立都有着不容忽视的影响。文章在对EAST真空室简化和划分的基础上,求解出真空室上感应涡流在等离子体击穿阶段的分布,对环电压的建立和零场区的变化情况进行了有效模拟。     

Selection of Spectral Data for Classification of Steels Using Laser-Induced Breakdown Spectroscopy

Principal component analysis (PCA) combined with artificial neural networks was used to classify the spectra of 27 steel samples acquired using laser-induced breakdown spec?troscopy. Three methods of spectral data selection, selecting all the peak lines of the spectra, selecting intensive spectral partitions and the whole spectra, were utilized to compare the influ?ence of different inputs of PCA on the classification of steels. Three intensive partitions were selected based on experience and prior knowledge to compare the classification, as the partitions can obtain the best results compared to all peak lines and the whole spectra. We also used two test data sets, mean spectra after being averaged and raw spectra without any pretreatment, to verify the results of the classification. The results of this comprehensive comparison show that a back propagation network trained using the principal components of appropriate, carefully se?lected spectral partitions can obtain the best results. A perfect result with 100% classification accuracy can be achieved using the intensive spectral partitions ranging of 357-367 nm.     

CPR1000反应堆压力容器制造无损检验与役前检查不一致的问题分析

重点分析RCC-M和RSE-M规范的无损检验要求,梳理出中国改进型三环路压水堆(CPR1000)反应堆压力容器(RPV)制造无损检验与役前检查要求的差异项。对差异项开展分析研究,从检验范围、扫查方向、记录水平、显示尺寸测量和评价标准等方面提出针对性的技术改进方案,尽可能解决由于制造和役前检查技术差异而产生检验结果不一致的工程问题。     

Second trip system for NRU research reactor

For the past four decades, the NRU research reactor has played an important role at the Chalk River Laboratories, Atomic Energy of Canada Limited, serving as one of its major research and isotope production facilities. To ensure that it continues as an effective facility, compliant with the current safety standards, a comprehensive upgrade program is underway. Adding a second trip system (STS) is part of this upgrade program, aiming at improving the effectiveness and reliability of the overall shutdown function. This document describes the main features and basic principles of the STS.The STS is an independent, seismically qualified trip system, that guarantees reactor shutdown even if the existing trip system fails. It is designed based on 2 out of 3 general coincidence logic, with minimal interferences and changes to the existing system. In addition to the manual trip in the main control room, a remote manual trip is provided in the new Qualified Emergency Response Centre, which is also seismically qualified and always accessible. Thus, for any reason, if the main control room becomes uninhabitable, the reactor still can be manually shut down from this centre.     

Breakdown of Dielectrics Due to Pulsed Electrons

Spontaneous dielectric breakdown was studied in methyl methacrylate polymer, Plexiglas, with a Field Emission Corporation Model 705 Febetron. The breakdown plane was influenced by the presence of embedded metal foils. Charge deposition was measured in a stack of thin sheets of Plexiglas and compared favorably with the calculated charge deposition under the condition of no charge buildup. The energy deposition behind samples of Plexiglas showed a reduction with increased sample thickness. An incident charge density of 4.l × 10-2 coulombs/M2 was found necessary to cause spontaneous breakdown in samples thicker than the electron range. The time between the deposition of maximum charge and spontaneous dielectric breakdown was 30 to 40 nanoseconds for an 1/8-inch thick sample with 7.4x10-2 coulombs M2 of incident electrons on an 1/4-inch diameter area. When Plexiglas was irradiated to 7.4x10-2 coulombs/M2, 1/16-inch thick samples did not show breakdown whereas 1/10-inch thick samples did show breakdown.     

Preliminary Thermal Mechanical Analysis of the Equatorial Thermal Shield for ITER

Thermal analysis of the equatorial thermal shield for ITER is conducted in order to confirm that the cooling tube design was reasonable under both the plasma operational and the baking operational conditions. The structural performance was analyzed by means of the finite element software ANSYS. A comparison of the results with design requirements shows that the results of the simulation are within allowable design requirements, which indicates the feasibility and reliability of the equatorial thermal shield structure.     

Methods of Data Processing for Trace Elements Analysis Using Laser Induced Breakdown Spectroscopy

With the development of Laser Induced Breakdown Spectroscopy (LIBS), increasing numbers of researchers have begun to focus on problems of the application. We are not just satisfied with analyzing what kinds of elements are in the samples but are also eager to accomplish quantitative detection with LIBS. There are several means to improve the limit of detection and stability, which are important to quantitative detection, especially of trace elements, increasing the laser energy and the resolution of spectrometer, using dual pulse setup, vacuuming the ablation environment etc. All of these methods are about to update the hardware system, which is effective but expensive. So we establish the following spectrum data processing methods to improve the trace elements analysis in this paper: spectrum sifting, noise filtering, and peak fitting. There are small algorithms in these three method groups, which we will introduce in detail. Finally, we discuss how these methods affect the results of trace elements detection in an experiment to analyze the lead content in Chinese cabbage.     

New Breakdown Electric Field Calculation for SF6 High Voltage Circuit Breaker Applications

The critical electric fields of hot SF6 are calculated including both electron and ion kinetics in wide ranges of temperature and pressure, namely from 300 K up to 4000 K and 2 atmospheres up to 32 atmospheres respectively. Based on solving a multi-term electron Boltz- mann equation the calculations use improved electron-gas collision cross sections for twelve SF6 dissociation products with a particular emphasis on the electron-vibrating molecule interactions. The ion kinetics is also considered and its role on the critical field becomes non negligible as the temperature is above 2000 K. These critical fields are then used in hydrodynamics simulations which correctly predict the circuit breaker behaviours observed in the case of breaking tests.     

固态继电器电磁脉冲损伤阈值试验不确定度评定

国军标GJB538-88<半导体器件电磁脉冲损伤阈值试验方法>中没有不确定度评定的说明,根据该标准进行了固态继电器电磁脉冲损伤阈值试验,给出了试验测量不确定度评定的方法和步骤,并详细讨论了破坏性试验不确定度评定的特殊性.结果可供半导体器件电磁脉冲损伤阈值试验参考.