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。     

正电子CT三维成象方法

本文阐述依据平行丝室检测的二维信息,实现滤波反投影成象的数学方法。介绍伪三维和全三维两种图象重建方式,以及一种适于采用的点响应函数定义。此外,给出全三维法的参数设计和计算步骤。     

一种分辨电子和X射线的多丝室系统

研制了一种能够分辨电子和Ｘ射线的多丝室系统，作为穆斯堡尔谱仪的探测器，可以同时测量样品吸收共振辐射后发射的特征Ｘ射线和内转换电子及俄歇电子的穆斯堡尔谱，从而得到样品表面不同深度的多种信息。     

Three-dimensional electric field calculations for wire chamber using element refinement method in ANSYS

Finite element analysis(FEA) method was employed to perform three-dimensional(3D) electric field simulations for gas detectors with multiple wire electrodes.A new element refinement method developed for use in conjunction with the FEA program ANSYS allows successful meshing of the wires without physically inputting the wires in the chamber geometry. First, we demonstrate a model with only one wire, for which we calculate the potential distributions on the central plane and the end-cap region. The results are compared to the calculations obtained using GARFIELD, a two-dimensional program that uses the nearly exact boundary element method. Then we extend the method to same model, but with seven wires.Our results suggest that the new method can be applied easily to the 3D electric field calculations for complicated gas detectors with many wires and complicated geometry such as multiwire proportional chambers and time projection chambers.     

Recent Developments in Delay Line Readout of Multiwire Proportional Chambers

The application of electromagnetic delay line readout methods for determining the track positions of ionizing particles in multiwire proportional chambers is described. Construction techniques for large area chambers, which allow the use of all three planes for track position measurements are given. The construction and characteristics of electromagnetic delay lines optimized for wire chamber readout are discussed.     

High-Accuracy Position Measurements with Drift Chambers and Proportional Chambers

By constructing multiwire drift chambers with a uniform electric field saturating the drift velocity, a perfectly linear response is obtained over all the chamber. The accuracy is close to ? = 100 ?m. A similar accuracy is obtained for inclined tracks and in magnetic fields of the order of 1 tesla. By measuring the centre of gravity of avalanches a very high accuracy is obtained in the measurement of the two coordinates of avalanches in a single gap of a proportional chamber. The applications of the method to the mapping of spatial distributions of soft X-rays are discussed.     

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.     

The Performance of a Multistep Proportional Counter for Use in X-Ray Astronomy

The addition of a parallel field preamplification region has been shown to dramatically improve the performance of a standard multiwire proportional counter, permitting high overall gas gains to be achieved, a prerequisite for good spatial resolution, without in any way compromising energy resolution. The resulting device, known as a multistep detector, has been tested over a wide range of operating conditions and fill gas mixtures. Results are presented here detailing the performance available with argon and xenon as the principle gases, these being of particular relevance to x-ray astronomy.     

氚深度分布对β射线诱发X射线光谱法测量能谱中Ar(Kα)强度的影响

BIXS(β射线诱发X射线光谱法)是一种针对材料中氚的无损测量方法,该方法通过探测氚在材料与工作气体(氩气)中诱发的特征X射线与轫致辐射X射线谱计算材料表层(β射线射程范围内)与基体中的氚含量与分布。通常认为氩的Kα特征峰强度与材料表层氚含量呈正比,然而该结论的前提是氚在材料表层均匀分布,而未考虑非均匀分布的情形。本文详细评估了氚在材料表层的深度分布对BIXS能谱中Ar(Kα)强度的影响,结果表明,在均匀分布的情况下,β射线最大射程的1/10范围内的氚对Ar(Kα)强度的贡献约为50%;在非均匀分布的情况下,Ar(Kα)的强度与均匀分布有数倍的差异。因此在实际测量中需根据氚在材料表层的具体分布对结果进行修正。     

Operation of the ATLAS muon drift-tube chambers at high background rates and in magnetic fields

In the ATLAS muon spectrometer, large drift-tube chambers are used for precision tracking. The chambers will be operated at a high neutron and /spl gamma/ background resulting in count rates of up to 500 Hz cm/sup -2/ corresponding to 300 kHz per tube. The spatial resolution of the drift tubes is degraded from 82 /spl mu/m without background to 108 /spl mu/m at 500 Hz cm/sup -2/ background count rate. Due to afterpulsing in the Ar/CO/sub 2/ gas mixture used in the drift tubes, ionizing radiation causes more than one hit in a tube within the maximum drift time of about 800 ns which is expected for magnetic field strengths around 1.2 T. In order to limit the count rate, the drift tubes are read out with an artificial dead time of 790 ns which causes an efficiency loss of 23% at a rate of 300 kHz per tube. The space-to-drift-time relationship of the tubes varies with background rate, temperature, and magnetic field strength. The mean magnetic field strength in a muon chamber is 0.4 T on the average, but may vary by up to 0.4 T within a chamber. The space-to-drift-time relationship must therefore be determined in short time intervals with an accuracy better than 20 /spl mu/m using muon tracks and applying corrections for measured magnetic field variations.     

高气压充氙多丝正比室

研制了一个高气压充氙多丝正比室。其灵敏面积近700cm~2,充以3个大气压的氙-甲烷混合气体(95％Xe+5％CH_4),可探测10—200keV的硬X射线。对~(241)Am的59.54keV X射线,单丝能量分辨率(FWHH)10％,全部阳极丝并联输出则为19％,对其29.8keV的逃逸峰则分别为17％和20％。在密封不流气状态下可工作数月而保持良好的能量分辨率。     

~（60）Co和~（137）Csγ射线参考辐射场及测定其空气比释动能（率）的系

本实验室建立了６０Ｃｏ和１３７ＣＳγ射线参考辐射场，并研制了不同体积的系列球形石墨空腔电离室，用于测定辐射场的空气比释动能率。对于３０ｃｍ３和５０ｃｍ３电离室，估计总不确定度为０．７４％，与国内照射量标准符合得相当好，与日本国家标准（ＥＴＬ）比对结果也在１％内相符。用这些电离室对本实验室所建立的６０ＣＯ和１３７ＣＳγ射线参考辐射场空气比释动能率（或照射量率）进行测定，与１９９０年ＭＣＤ－１００电离室测量结果都在２％内相符。     

Acoustic Detection for Small-Leak Sodium-Water Reaction

Characteristics of acoustic signal produced by sodium-water reaction due to steam injection and by Ar gas injection into sodium were experimentally investigated. Acoustic signal was measured by using Kistler 808A and 815A5 accelerometers. Root mean square (RMS) measurements and frequency analysis of the signal were conducted.

The RMS measurements could detect a small water leakage into sodium, as small as 0.07 g/sec, in the present loop. The peaks in a frequency spectrum were caused by the natural vibration of a rod on which the acoustic transducer was mounted.

The RMS was approximately proportional to the one-third power of the steam leak rate and increased to some extent with the ambient sodium temperature. RMS values, both for sodium-water reaction and Ar gas injection, were about the same order of magnitude, when the data were plotted against the volumetric flow rates of steam and Ar gas.     

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.     

多丝正比室的不对称结构和能量分辨率

多丝正比室对能谱的测量中发现，＾２４１Ａｍ的５９．６ｋｅＶ，谱线能峰呈双峰结构，电场分布计算，电子漂移过程分析及气体放大倍数的计算表明，丝室结构的非圆对称将导致；１）电子漂移到阳极丝的过程中扫过的电位差统计分析分布的展宽甚至出现双峰结构，２）气体放大倍数与电子到达方向有关，丝室电场分布的计算中采用了解析解和数值解相结合的方法。     

大面积流气式多丝正比计数管的空间电场强度分布及参数选择

为了解大面积流气式多丝正比计数管工作空间的电场分布,本文提出了近似计算的物理模型,并在设定的条件下进行了数值计算,得到了电场分布的近似结果及其某些参数,诸如丝距和电极间距等的关系,以便于多丝正比计数管的正确设计和使用。     

内充气正比计数管测量37Ar活度中壁效应的理论研究

通过分析³⁷Ar衰变产生的X射线和俄歇电子在内充气正比计数管灵敏体积中的逃逸及计数管在³⁷Ar活度测量中的壁效应,得出X射线在正比计数管中的逃逸是产生壁效应的主要原因,提出了压力指数外推方法。使用MCNP模拟X射线和俄歇电子在内充气正比计数管中的输运,模拟结果与理论分析结论一致。比较模拟得出的壁效应值与实验测量的壁效应值可知,实验给出的壁效应值是可信的。本工作的研究结果为37Ar测量方法提供了理论支持。     

Effect of O2 in O2/Ar Gas Mixture on Morphological and Optical Properties of TiO2 Thin Films Deposited by DC Cylindrical Magnetron Sputtering

TiO₂ films have been deposited on BK7 substrates by DC cylindrical magnetron sputtering setup in ambient temperature. The samples were fabricated at various O₂/Ar reactive gas mixtures. The effects of changing O₂ amount in O₂/Ar reactive gas mixture on structural, morphological and optical properties of films were studied. The thickness of films was measured by surface profile meter. Thickness of films decreases with increasing the O₂ amount in gas mixture. XRD studies shows that the films are amorphous. Atomic Force Microscopy was used to evaluate and compare the surface roughness and morphologies. The optical properties (transmission and reflection) of the samples were measured by UV–Vis–NIR spectrophotometer. Results show that increasing the O₂ amount in O₂/Ar mixture changes the surface morphologies and optical properties of films. All films exhibit a transmittance higher than 65 % in the visible region. The band gap of films was calculated from the optical measurements. The band gap of TiO₂ thin films increases from 3.471 to 3.526 for different O₂/Ar amounts.     

87Krγ射线发射几率的测定

用相对效率为60%的HPGe探测器测量⁸⁷Kr的相对γ射线发射几率和用内充气正比计数管绝对测量⁸⁷Kr放射性浓度。实验上测得了⁸⁷Krγ射线发射几率。其中，402.6keVγ射线发射几率的测量结果为（49.9±1.2）％。 