Radiation dosimetry using three-dimensional optical random access memories

Three-dimensional optical random access memories (3D ORAMs) are a new generation of high-density data storage devices. Binary information is stored and retrieved via a light induced reversible transformation of an ensemble of bistable photochromic molecules embedded in a polymer matrix. This paper describes the application of 3D ORAM materials to radiation dosimetry. It is shown both theoretically and experimentally, that ionizing radiation in the form of heavy charged particles is capable of changing the information originally stored on the ORAM material. The magnitude and spatial distribution of these changes are used as a measure of the absorbed dose, particle type and energy. The effects of exposure on 3D ORAM materials have been investigated for a variety of particle types and energies, including protons, alpha particles and 12C ions. The exposed materials are observed to fluoresce when exposed to laser light. The intensity and the depth of the fluorescence is dependent on the type and energy of the particle to which the materials were exposed. It is shown that these effects can be modeled using Monte Carlo calculations. The model provides a better understanding of the properties of these materials. which should prove useful for developing systems for charged particle and neutron dosimetry/detector applications.     

静态随机存取存储器质子单粒子效应实验研究

描述了测量静态随机存取存储器质子单粒子翻转截面的实验方法。采用金箔散射法可以降低加速器质子束流五六个量级,从而满足半导体器件质子单粒子效应的要求。研制的弱流质子束流测量系统和建立的注量均匀性测量方法解决了质子注量的准确测量问题。提高了存储器单粒子效应长线测量系统的性能,保证了翻转数的准确测量。实验测得静态随机存取存储器质子单粒子翻转截面为１０＾－１４ｃｍ＾２／ｂｉｔ量级,随质子能量的增大略有增大。     

静态随机存取存储器重离子单粒子翻转效应实验研究

应用重离子加速器和 2 52 Cf源进行单粒子翻转效应实验 ,测量得到 IDT系列和 HM系列静态随机存取存储器的单粒子翻转重离子 L ET阈值为 4～ 8Me V· cm2 /mg,单粒子翻转饱和截面为 10 -7cm2 · bit-1量级 ,位单粒子翻转截面随集成度的提高而减小。实验结果表明 ,可以用 2 52 Cf源替代重离子加速器测量静态随机存取存储器的单粒子翻转饱和截面     

Void measurement using high-resolution gamma-ray computed tomography

We present a high-resolution gamma-ray computed tomography (CT) measurement system for the determination of cross-sectional time-averaged void distributions in thermo hydraulic facilities. The system has been carefully designed for harsh operating conditions, such as varying temperature fields and strong magnetic fields, typically produced by thermal hydraulic test loops with direct electric bundle heating. Measurements are non invasive, thus the two-phase flow in the test section is not influenced. The gamma-ray CT system consists of a collimated ¹³⁷Cs isotopic source, a gamma radiation detector arc including 320 single elements, a pulse processing unit and a thermal stabilisation unit. The spatial resolution of the CT system is about 2 mm in plane. Recently, the thermal design of the detector arc is improved to secure maintenance of constant temperature of thermally sensitive components under changing environmental conditions. This turned out to be a key issue for achieving accurate quantitative measurements. First results of laboratory measurements on a bundle mock-up with this improved system are presented.     

Surface investigations using monolayer-resolvable high-resolution Rutherford backscattering spectroscopy

Energy spectra of scattered 0.5 MeV He ions from a clean (001) surface of SnTe are measured with a 90° sector magnetic spectrometer (ΔE/E 0.1%). The ions scattered from successive atomic layers can be resolved in the energy spectra. Inelastic energy losses and charge state distributions of 0.5 MeV He ions scattered from the topmost atomic layer of the SnTe(001) are measured. A position-dependent stopping power at the surface is proposed from the observed energy losses. The observed charge state distribution shows the importance of the charge-exchange processes with valence electrons in the tail of the electron distribution at the surface.     

Heavy ion-induced single event upset sensitivity evaluation of 3D integrated static random access memory

Heavy ion-induced single event upsets(SEUs)of static random access memory(SRAM), integrated with three-dimensional integrated circuit technology, are evaluated using a Monte Carlo simulation method based on the Geant4 simulation toolkit. The SEU cross sections and multiple cell upset(MCU) susceptibility of 3D SRAM are explored using different types and energies of heavy ions.In the simulations, the sensitivities of different dies of 3D SRAM show noticeable discrepancies for low linear energy transfers(LETs). The average percentage of MCUs of 3D SRAM increases from 17.2 to 32.95%, followed by the energy of ~(209)Bi decreasing from 71.77 to 38.28 MeV/u. For a specific LET, the percentage of MCUs presents a notable difference between the face-to-face and back-toface structures. In the back-to-face structure, the percentage of MCUs increases with a deeper die, compared with the face-to-face structure. The simulation method and process are verified by comparing the SEU cross sections of planar SRAM with experimental data. The upset cross sections of the planar process and 3D integrated SRAM are analyzed. The results demonstrate that the 3D SRAM sensitivity is not greater than that of the planar SRAM. The 3D process technology has the potential to be applied to the aerospace and military fields.     

Development of local-scale high-resolution atmospheric dispersion model using large-eddy simulation. Part 3: turbulent flow and plume dispersion in building arrays

We have developed a LOcal-scale High-resolution atmospheric DIspersion Model using Large-Eddy Simulation (LOHDIM-LES) to assess the safety at nuclear facilities and to respond to emergencies against accidental or intentional release of radioactive materials (e.g., a terrorist attack in an urban area). In Part 1, the unsteady behavior of a plume over a flat terrain was successfully simulated. In Part 2, a new scheme to generate a spatially developing turbulent boundary layer flow was proposed. Then, the large-eddy simulation (LES) model for turbulent flow and plume dispersion around an isolated building was validated. In this study, we extend the LES model to turbulent flows and plume dispersion in various building arrays that represent typical urban surface geometries. Concerning the characteristics of flow and dispersion in building arrays, the flow patterns associated with obstacle densities and the distribution patterns of mean and root-mean-square (r.m.s.) concentrations agree well with those of the wind tunnel experiments. It is shown that the LES model successfully simulates the unsteady behaviors of turbulent flows and plume dispersion in urban-type surface geometries.     

Chemical shift measurements of chlorine K X-ray spectra using a high-resolution PIXE system

A high-efficiency high-resolution wavelength-dispersive spectrograph with a von-Hamos configuration was developed for chemical state identification of elements in environmental samples using PIXE analysis. To evaluate the performance of this system, chlorine K X-ray spectra for NaCl, NH₄Cl and polyvinylchloride (PVC) targets were measured and compared. Also, to study the applicability to environmental mixed samples, mixtures of NaCl and NH₄Cl with different mixing ratios were measured. Through observation of Cl Kα₁ X-ray from NaCl, the energy resolution of the system was determined to be 1.1 eV. For the NaCl sample, a Kβ_x line was observed at an energy, which is higher than that of the Kβ main peak by 2 eV, whereas no Kβ_x emission was observed for the NH₄Cl sample. The chemical shift of the Kβ main peak for PVC relative to that for NaCl was about 1.2 eV. For NaCl-NH₄Cl mixture targets, the relative intensity of Kβ_x satellite to the Kβ main line provided an indication of mixing ratio. Energies and relative intensity of Cl Kβ X-ray satellites for NaCl and NH₄Cl samples calculated by a simple molecular-orbital method agreed only qualitatively with the experimental results.     

Reduction method for residual stress of welded joint using random vibration

Welded joints are used for construction of many structures. Residual stress is induced near the bead caused by locally given heat. Tensile residual stress on the surface may reduce fatigue strength. In this paper, a new method for reduction of residual stress using vibration during welding is proposed. As vibrational load, random vibration, white noise and filtered white noise are used. Two thin plates are butt-welded. Residual stress is measured with a paralleled beam X-ray diffractometer with scintillation counter after removing quenched scale chemically. It is concluded that tensile residual stress near the bead is reduced by using random vibration during welding.     

核设备抗震鉴定试验目标PSD生成方法研究

为避免抗震鉴定试验用人工时程能谱特性失真,需满足功率谱密度80%包络的要求。从楼层反应谱、傅里叶幅值谱和功率谱密度之间的互相关系入手,开展楼层目标功率谱密度生成方法的研究。分别采用Kaul公式法和SRP3.7.1附录A快速傅里叶变换法,将楼层反应谱和人工加速度时程转换为功率谱密度。通过对比分析不同方法的基本假设和不确定性以及获得功率谱密度的形状、峰值的差异,推荐用生成楼层反应谱的原始响应时程进行快速傅里叶变换的方法作为目标功率谱密度的生成方法。     

Measurement of trace element content in bone samples using long-lived neutron activation products and high-resolution gamma-ray spectrometry

A nondestructive instrumental neutron activation analysis with high-resolution gamma-ray spectrometry of long-lived radionuclides was developed and used for measurement of trace element contents in samples of bone to determine health and diseases. Using this method, the silver(Ag), cobalt(Co), chromium(Cr), iron(Fe), mercury(Hg), rubidium(Rb), antimony(Sb), selenium(Se), and zinc(Zn) mass fractions were estimated in bone samples from 27 patients with intact bone(12 females and 15 males, aged from 16 to 49 years) who had died from various non-bone-related causes, mainly unexpected traumas,and from 5 patients with chondroma(2 females and 3males, 15–42 years old), obtained from open biopsies or after operation. The reliability of the differences in the results between intact bone and bone affected by chondroma was evaluated by a parametric Student's t test and a nonparametric Mann–Whitney U test. It was found that in the bone affected by chondroma, the mean mass fractions of Co, Cr, Fe, Se, Sb, and Zn were significantly higher than in normal bone tissues. In the neoplastic bone, many correlations between trace elements found in the control group were no longer evident. This work revealed that there is asignificant disturbance of the trace element metabolism in bone affected by chondroma.     

Single event upset immunity of strontium bismuth tantalateferroelectric memories

An embedded 1 Kbit nonvolatile (NV) serial memory manufactured with strontium bismuth tantalate (SBT) ferroelectric (FE) technology was shown to be immune to effects of heavy ion irradiation. The memories did not lose any data in the non-volatile mode when exposed to xenon (maximum effective LET of 128 MeV-cm²/mg and a total fluence of 1.5×10⁷ ions/cm²). The ferroelectric memories also did not exhibit any loss in the ability to rewrite new data into the memory bits, indicating that no significant degradation of the FE dipoles occurred as a result of the heavy ion exposure. The fast read/write times of FE memories also means that single event gate rupture is unlikely to occur in this technology     

高速高精度数据采集系统设计和实现

为了满足高速数据采集,尤其是红外焦平面信号的高速采集要求,设计了一个基于VXI总线的30M SPS 16BIT的三通道数据采集系统.该采集系统的可扩展性和灵活的采集和处理方式,使它不仅可以用于红外CCD(电荷耦合器件)图像信号采集的处理,还可以应用于其他高性能采集和测试系统中.本文对CDS(相关双采样)时钟控制电路,A/D转换及其接口电路,VXI总线接口电路,存储器接口电路等关键技术进行了详细论述.     

随机游走大气扩散模型在核事故应急中的开发和应用

烟羽浓度预测是核事故早期应急响应放射性后果评价系统的主要内容之一.描述了大气扩散本身随机的特点,介绍了自行开发随机游走大气扩散模型Random Walk,并与现有欧共体开发的核应急决策支持系统RODOS中的拉格朗日烟团模型RIMPUFF进行比较验证.结果表明,两者计算结果相当吻合,但Random Walk计算出的烟羽范围比RIMPUFF计算出的稍小.随机游走大气扩散模型Ran-dom Walk能够较好的模拟核事故发生条件下的大气扩散过程,可以作为核事故应急决策系统的一个大气扩散模块,为早期应急和后果评价提供更接近实际的信息.     

PSD位置测量系统在波荡器磁场测量中的应用

位置敏感探测器(Position Sensitive Detector,PSD)是一种基于横向光电效应(x和y方向)的光电位置敏感器件,可直接探测到入射光斑的能量中心位置,在波荡器磁测中可用于获得霍尔探头测量过程中的横向位置变化。为了在狭小或封闭空间内实现对波荡器(尤其是真空内波荡器)磁场进行高精度的测量,我们设计并搭建了测试系统,对导轨直线度(x和y方向)进行了测量。实验结果表明,该位置测量系统具有5μm的测量精度,可以满足霍尔探头在波荡器磁测过程中的位置精度要求。     

Response of nuclear structural systems to transient and random excitations, using both deterministic and probabilistic methods

The finite element is commonly used for the static analysis of reactor components and the same ideas can be applied to the dynamic analysis. The formation of various damping matrices for both internal and external damping is discussed. For the most part only the linearized form of the equations of motion is considered giving

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. The type of solution adopted depends upon both the force input and the required response. For a short period transient input usually only the initial response is required which is best found from a step-by-step integration. A method involving a Taylor series and curve fitting over a series of steps is developed and applied to the solution of a beam subject to a pressure transient.For a periodic force input the steady state response is needed requiring the determination of the damped eigenvectors. An efficient algorithm, using the undamped vectors, is given and the response to an arbitrary force input developed. This method is applied to the previous example and the two solutions are compared illustrating the advantages and disadvantages of each method. For random excitation methods of presenting information are discussed standard results for the stationary problem are presented in terms of the first part of the paper. As an example the spectral density of the response due to random imposed movements is given illustrated by a series of heat exchange tubes excited by random forces. The response due to a non-stationary force input such as an earthquake is discussed. The step-by-step method of analysis is used to predict the probability density function of the response of a simple system at any time under such a non-stationary input. Possible modes of failure with reference to reactor components are discussed and indications of how the proceeding theory can be applied to predicting failures are given.     

Ion beam studies of events typical of soft errors in semiconductor memories

A fast ion microbeam has been used to study phenomena associated with soft errors in semiconductor memories. A spatially small beam with a fast blanking system is used to study both alpha particle and heavy ion strikes. The heavy ion strikes are typical of the recoil from cosmic-ray-generated neutrons. Charge collection and static RAM error-rate experiments are discussed.     

Theoretical remarks on the statistics of three discriminants in Piety's automated signature analysis of PSD data

Piety (1977) proposed an automated signature analysis of PSD data. Eight statistical decision discriminants are introduced. For nearly all the discriminants, improved confidence statements can be made. In this paper, we consider the statistical characteristics of the last three discriminants which are applications of non-parametric tests.     

Experiments on slug mixing under natural circulation conditions at the ROCOM test facility using high-resolution measurement techniques and numerical modeling

ROCOM is a four-loop test facility used for the investigation of coolant mixing in the primary circuit of pressurized water reactors. Recently, a new sensor was developed for an improved visualisation and quantification of the coolant mixing in the downcomer. This new sensor array spans a dense measuring grid and covers nearly the whole downcomer. In the presented work, special emphasis was given to the comparison of the data of this sensor with the results of calculations using the Computational Fluid Dynamics (CFD) code ANSYS CFX. A coolant mixing experiment during natural circulation conditions has been conducted. The underlying scenario of this experiment is based on a boron dilution scenario following a SBLOCA event. The corresponding CFD code solution has been obtained using the Best Practice Guidelines. All main effects observed in the measurement are described by the calculation. The detailed comparison reveals that the calculation underestimates the coolant mixing inside the reactor pressure vessel.The measurement data, boundary conditions of the experiment and facility geometry can be made available to other CFD code users for benchmarking.