北京谱仪端盖簇射计数器工作气体的研究

为使北京谱仪端盖族射计数器更好地工作在自猝灭流光ＳＱＳ模式下，提高其能量分辨以及线性等指标，用Ａｒ，ＣＯ２，Ｌｓｏｂｕｔａｎｅ三元工作气体对探测器的工作性能进行了仔细研究，找出了一适合于主雇地数器的工作气体，此外，还研究了异丁的纯度对探测器性能的影响。     

小型活性靶时间投影室性能研究

本文设计了使用64路一维读出条的小型活性靶时间投影室,并对其性能进行了测试,其气体室的灵敏体积为10 cm×10 cm×14 cm,通过连接2层厚气体电子倍增器进行电子放大。为改善场笼边缘的电场不均匀性,引入场笼环的设计结构。当场笼环加高压为-950 V时,测得α粒子沿漂移电场方向的径迹位置分辨小于02 mm,径迹角度分辨小于0.6°,时间分辨小于20 ns。活性靶时间投影室的工作气体为96%He+4%CO₂。实验中也观察到了清晰的α粒子在He气上的弹性散射事件。     

薄窗型多阳极气体探测器研究进展

薄窗型气体探测器是最近发展并用于低能量加速器质谱探测技术。该探测器的入射窗采用氮化硅膜,薄而均匀,分辨率高,目前已在低能量粒子探测技术中得到初步应用,显示出广泛的应用前景。本文主要从薄窗型气体探测器基本原理、薄氮化硅膜与Mylar膜的对比、不同质子数Z的低能量粒子脉冲高度对比、薄窗型气体探测器与硅探测器的对比,以及应用等方面进行阐述。     

Advances in CTIX Accelerator Study

Several new experiments have been conducted on the UC Davis repetitive-pulsed spheromak-like compact toroid (SCT) accelerator (CTIX). (1) SCT density and kinetic energy density has been increased by gas puffing in the acceleration section. With gas puffing, SCT electrical to kinetic energy conversion efficiency has been increased to >20%. (2) SCT interaction with targets has been recorded with a fast visible imaging system, combined with target-region helium gas puffing for increased brightness. Images of both coherent waves and turbulent flow patterns were observed in the target region after the interaction. (3) A laser deflection density diagnostic has been improved to obtain better reliability and resolution. Operated with high-density gas-puffed SCTs, the second-generation diagnostic has successfully measured axial as well as radial deflection. The measured line averaged densities are in good agreement with a conventional quadrature laser interferometer.     

Study and optimization of multiwire proportional chambers for Synchrotron facilities

Multiwire proportional chambers (MWPCs) are widely used in many different disciplines. The quality of the results depends on many factors such as gas gain, detector count rate, detection efficiency, spatial and energy resolution, and uniformity. We report here on a detailed study on how to optimize all these features, in particular regarding the use of MWPC at synchrotron radiation sources. Detector behavior has been analyzed in relation to geometry of the wire planes; electric field; frames design and window geometry; and gas parameters. From this study, general optimization criteria were obtained. The results of this study have been applied to produce a new design for a detector required to perform time-resolved X-ray diffraction/scattering experiments in the submillisecond time scale with a spatial resolution of 0.03 cm. In addition, we report on the outcome of simulations aiming at understanding the influence of manufacturing defects as well as gas quality.     

用于CSNS反角白光中子源的双屏栅电离室设计及性能研究

为测量中国散裂中子源（China Spallation Neutron Source, CSNS）反角白光中子源150 keV以下能区飞行时间法中子能谱,研制基于¹⁰B(n, α)⁷Li和⁶Li(n, t)α核反应的双屏栅电离室,采用薄窗和薄底衬的结构设计。通过Garfield++、SRIM和Simcenter Magnet Electric程序对屏栅电离室的工作气体、极间距和电场分布等工作参数进行模拟设计,并采用α源及CF₄、P10、90%Ar-10%CO₂三种气体对电离室进行性能参数测试。结果表明,选定电子漂移速度快、扩散系数小,以及阻止本领大的CF4作为CSNS/Back-n束上测试工作气体,阴极-栅极和栅极-阳极间距分别为20 mm和5 mm。屏栅电离室收集区74 mm范围内是电场均匀区,场强的相对偏差≤0.03%;性能测试结果表明,工作气体为CF₄时,电离室对²³⁹Pu/²⁴¹Am/²⁴⁴Cm混合α面源具有很好的能量分辨,最佳能量分辨率为2.4%@5.48 MeV。对比平板型电离室和硅微条探测器的测量结果,验证了本工作研制的屏栅型电离室的能量分辨优势。     

基于微通道板的电离室及其在同步辐射中的应用

在同步辐射装置中,气体电离室是定标光束线能量和评估能量分辨率的一个重要实验装置。为了摆脱电极探针式电离室的气体展宽对束线能量分辨率测定的限制,本文将微通道板(Microchannel Plate,MCP)应用于同步辐射光束线中的电离室,研制成功了具有高能量分辨率的电离吸收谱的探测系统。利用此系统测量标准气体在X射线入射时的电离吸收谱,通过分析测量所得谱线中吸收峰的展宽,可获得光束线的仪器展宽,本文以Ar的吸收谱为例给出了测量结果。     

平行板气体闪烁正比管

本文简述了气体闪烁正比管的原理、基本结构和制作工艺,对~(55)Fe 5.9keV X射线得到的能量分辨率约为9％。     

放射性气体活度测量

研制了一套放射性气体活度测量装置及配套测量系统,研究考查了放射性气体活度测量装置及标准测量系统的性能和技术指标;实际测量了放射性气体活度并评定了其不确定度;对放射性气体活度测量系统量值传递技术进行了研究。整套装置技术指标满足有关标准、规范和规程要求,可作为工作标准对我院放射性进行常规测量、检定。     

A new glass GEM with a single-sided guard-ring structure

The gas electron multiplier (GEM) is a gaseous detector that is widely used in many applications. Our glass GEM (G-GEM) comprises a photo-etchable glass (PEG3, HOYA Corporation, Japan). Our research indicated that it shows superior performance compared with other gas detectors. In this article, a new type of G-GEM is introduced. It has a guard-ring structure around the holes in order to improve the spark tolerance by reducing the total capacitance of each hole structure. A measured gas gain of approximately 7500 is attained for this new G-GEM with a single-sided guard-ring structure using a gas mixture of Ar (90%) and CH₄ (10%) in the gas flow mode. An energy resolution of 17.3% (FWHM) is also achieved with a collimated 6 keV X-ray beam. The results of a 10 to 12 hour gas gain stability measurements are also shown.     

New Near-Infrared and Ultraviolet Gas-Proportional Scintillation Counters

New studies of gas-proportional scintillation counters have been performed using a large alpha source, reasonable spectral resolution (< 25-k), and including the strong near-infrared transitions in noble gases excluded in all previous studies. The results indicate that several new gas mixtures show promise for detectors to measure the neutron fluxes in a reactor over a wide range of values and in many nuclear physics applications where fast response and good energy resolution are desired. When used with an isotopic source the device can be used as a portable, variable-intensity light source or to detect trace amounts of atmospheric contaminants such as CO, NO, and Hg. The work also has provided useful data for laser systems pumped by ionizing radiation as well as for the operation of plasma display panels.     

A compact gamma-ray detector using wavelength-shifting fibers coupled to YAP scintillation crystal

The performance of a compact position sensitive gamma-ray detector based on wavelength-shifting fibers coupled to YAlO3：Ce scintillation crystal was evaluated using a Monte-Carlo simulation method. The simulation model has been setup using the GEANT4 codes. Compared with the gamma-ray detector based on the YAlO3：Ce scintillation crystal coupled to Hamamastu R2486 position sensitive photomultiplier tube, the results indicate that the gamma-ray detector based on wavelength-shifting fibers readout has good position linearity, good spatial resolution and larger effective field of view. The image and point spread function of measured point were presented. The spatial resolution response as a function of position was obtained. The factors influencing spatial resolution and position linearity were discussed.     

Modeling of the Helium-Heated Steam Reformer for HTR-10

In this study, based on the pseudo-homogeneous one-dimensional model, a steady-state model of the helium-heated steam reformer planned to be connected with the 10 MW high temperature gas cooled reactor (HTR-10) has been developed. Good agreement is shown between the simulating results and experimental data. The influence of main process parameters on the performance with respect to the methane conversion and the hydrogen yield is investigated and discussed. The performance increases remarkably with the increase in the inlet helium temperature when it is lower than 1,000°C. Whereas, the effect becomes weak when the temperature is higher than 1,000°C. The influence of the inlet helium flow rate is not as evident as that of the temperature. The inlet helium pressure and inlet process gas temperature have almost no influence on the performance. The performance increases with the decrease in the inlet process gas pressure. The influence of the inlet process gas flow rate and steam-to-carbon ratio (S/C) is complicated. Optimal values should be chosen for them to obtain a high performance.     

正比室一些特性的研究

本文描述了簇射计数器中的正比室模型。研究了正比室所使用的气体CH_4/Ar和Co_2/Ar的特性。使用~(55)FeX射线源研究了气体放大系数和能量分辨率与气体成份和丝直径的关系。也给出了正比室坪特性与气体成份的关系。 关于~(55)FeX射线谱的两个峰,提出了与文献[4]不同的解释。     

Schwarzschild microscopes in vacuum ultraviolet and soft X-ray regions

Microscopes in vacuum ultraviolet and soft X-ray regions using a normal incidence type of Schwarzschild objective are reviewed. The objective consists of a concave mirror and a convex mirror coated with a high reflectance multilayer, having a large numerical aperture comparing with other objectives. The microscopes have been used to diagnose inertia-confinement-fusion plasmas, and to investigate small samples or microstructures of inorganic and organic materials by imaging them using laboratory light sources. Synchrotron radiation has been also used to obtain a microbeam for a photoelectron scanning microscope with a spatial resolution of 0.1 μm. The structure and performance of two laboratory microscopes developed at Tohoku University are demonstrated. One of them is a soft X-ray emission imaging microscope, An image of an artificial pattern made of W and SiO2 on Si wafer by focusing Si L emission was presented, The other is an ultraviolet photoelectron scanning microscope using a He (helium) gas discharge lamp. The valence band spectra of a microcrystal of FeWO4 were presented, Furthermore other applications such as demagnifying optics for lithography and optics to gather fluorescence for emission spectroscopy are introduced.     

Annular gas ionization detector for low energy heavy ion backscattering spectrometry

A gas ionization chamber for use in backscattering spectrometry has been built. It has the shape of a hollow cylinder and can be placed in-line with the incident ion beam. The entrance window for detected particles is composed of a circular array of silicon nitride membranes. A low noise preamplifier with cooled FET is used for charge amplification. The detector resolution has been measured for a variety of ions in the mass range from He to Si and for energies between 0.5 and 8 MeV. The energy resolution of the ionization chamber surpasses the one of a state-of-the-art silicon charged particle detector for all ions heavier than Li. For Si ions the improvement in resolution is more than a factor of 2. The device does not suffer from any radiation damage. For He particles around 1 MeV the resolution is between 13 and 16 keV (FWHM). Therefore the new detector is not only well suited for heavy ion backscattering spectrometry but can also be applied for standard He RBS, allowing the use of a single detector for all types of projectiles in a wide energy range.     

A four-gap glass-RPC time-of-flight array with 90 ps timeresolution

In this paper, we describe the performance of a prototype developed in the context of the ALICE time-of-flight research and development system. The detector module consists of a 32-channel array of 3×3 cm² glass resistive plate chamber (RPC) cells, each of which has four accurately spaced gaps of 0.3 mm thickness arranged as a pair of double-gap resistive plate chambers. Operated with a nonflammable gas mixture at atmospheric pressure, the system achieved a time resolution of 90 ps at 98% efficiency with good uniformity and moderate crosstalk. This result shows the feasibility of large-area high-resolution time-of-flight systems based on RPCs at affordable cost     

Comparative Timing Performance of Large Volume Ge(Li) and HPGE Coaxial Detectors

The timing performance of several large (8% to 12% relative efficiency) Ge(Li) and HpGe coaxial detectors has been measured and compared. The Ge(Li) detectors are capable of timing resolution which is generally 10% to 30% better than that of the HpGe devices. This resolution capability can be attributed to the higher bias voltages which can be applied to the Ge(Li) detectors. However, in some applications that involve a wide dynamic range of energies, the HpGe devices can provide better timing resolution than their Ge(Li) counterparts. Advancements in the state of the art are expected to result in HpGe detectors that can provide timing performance equivalent to the performance of the best Ge(Li) devices.     

A UHV-compatible ΔE−E gas telescope for depth profiling and surface analysis of light elements

We have developed a compact ΔE−E gas telescope that can easily be incorporated into a standard ultrahigh vacuum ion scattering chamber. If energetic, heavy ions are available as a primary beam, the gas telescope can be used to detect light elastic recoils scattered from the surface region of a sample. The detector consists of a gas ionization chamber in front of a surface-barrier detector. The energy loss signal in the gas (ΔE) is taken in coincidence with the energy signal in the surface-barrier detector (E) to identify both the atomic number and the total energy of the elastic recoil. The design parameters of the detector have been chosen to allow detection of elements from H to O with good depth resolution ( < 100 Å) and submonolayer sensitivity. The mass resolution is adequate to easily separate all elements from H to O.