Printed Low Velocity Delay Lines for Cathode Readout of Proportional Chambers

A new type of flat delay line was developed which has a low propagation velocity and very good delay to rise time ratio. It can be constructed by printed circuit techniques without crossovers. The magnetic loops of a shifted periodic structure yield high inductance per unit length. Geometric scaling factors are shown. This line, forming the cathode plane of a proportional chamber, allows simultaneously, a satisfactory induced signal and the readout of the second coordinate by time delay without disturbing the electric field configuration around the anode. Optimization of position resolution vs. noise is discussed. Experimental results are shown. Other properties of such delay lines are discussed.     

Characteistics of Multiwire Proportional Chambers for Positron Imaging

We describe multivire proportional chambers (MWPC) designed for use in a positron camera for Nuclear Medicine applications. The coordinates of the two annihilation gamma rays are detected in the chamber by their interaction with thin lead converters placed on both faces of each chamber. In order to obtain reasonable efficiencies (10%) the lead converters have been made in a square honeycomb-like structure, which increases the effective surface area and also permits the application of a drift field to extract the electrons into the active area of the MWPC.     

Response of Multiwire Proportional Chambers to Relativistic Heavy Nuclei

Measurements have been carried out at the Lawrence Berkeley Laboratory Bevatron to investigate the response of multiwire proportional chambers to 2. 1 GeV/nucleon C12 and O16 nuclei. The relative gas gain as a function of high voltage was measured for three different gases: 80% Ar/20%CO2, 75% Ar/ 25%C4H10, and 81% Ar/14% Xe/5%CO2. The gas gain obtained with 5.9 KeV X-rays from Fe55 sources was also measured for comparison. Saturation characteristics of the chambers are analyzed and the implications of the results on the use of multiwire proportional chambers as spatial detectors in cosmic ray experiments are discussed. A summary of the results of delta ray calculations and their effect on spatial resolution is also presented.     

Recent Developments in Spark Chambers

The parallel developments of a variety of spark-chamber schemes have produced many workable systems with success in experimental applications. Major efforts have developed several methods for direct electrical readout of spark-chamber data. These include the use of magnetic cores for direct digitizing of information from wire spark chambers, as well as the use of Vidicon cameras to observe sparks, and of current division and acoustic transit time in analogue devices to measure spark position. For such systems the on-line use of computers, and (or) the construction of significant electrical interfacing circuitry, are important considerations in efforts to maximize the event rate. Conventional spark-chamber systems using film to record data have benefited from the continued development of automatic off-line scanning and measuring systems. There are also many experiments that will use the unique capabilities of wide-gap spark and streamer chambers.     

Operating Characteristics and Applications of Multiwire Proportional Counters

Multiwire proportional counters have proved to be very useful for a wide variety of experiments at all energies. Properties of these detectors essential in planning an experiment, e.g. their efficiency as a function of position and their output timing, have been measured. Integrated circuit amplifier-discriminators have been developed for use with multiwire arrays and operated in the typical large accelerator environment. An experiment on the scattering of pions and protons by complex nuclei has been performed with 8-inch square arrays of proportional counters used for x, y hodoscopes.     

多丝正比室中电子的最大漂移时间

多丝正比室中电子的最大漂移时间是逃逸门电路中的一个重要参数。这个参数的选择将影响逃逸门工作方式的多丝正比室的整体性能。通过实验测量得到了多丝正比室中电子的最大漂移时间的实际值和最大漂移时间随多丝正比室工作状态的变化，测量结果在实际中得到应用。     

Second Coordinate Readout in Drift Chambers by Charge Division

The drift time measurement and the charge division can be performed simultaneously on the same electrode (resistive anode) without affecting the accuracy of either measurement. It is shown that for the shortest measurement time there is an optimum value for the anode wire resistance. The signal requirement for a position uncertainty ? ? 0.5% of the anode wire length is only 2.7 x 106 electron charges. The drift chamber can be operated in the linear mode and with negligible space charge effects, so that it can also be used for ?E/?X measurements. A simple preamplifier optimized for both the time and charge measurements using a monolithic transistor array is described.     

Readout of Drift Chambers with a 100 MHz Flash ADC System

An electronic read out system for drift chambers, based on a 100 MHz Flash ADC is described. Test results are reported which include a study of the reproduction of the shape of fast chamber signals and measurements of the time and double track resolution. Measurements and computer simulations were performed to study the charge resolution.     

低压多丝正比室的位置分辨研究

低压多丝正比室为放射性束核反应的靶前粒子提供位置和时间信号。本工作用²⁴¹Amα源研究电压、工作气体压强等因素对低压多丝正比室位置分辨的影响。实验结果表明：在不同的气体压强条件下，低压多丝正比室的位置分辨均可达到1mm，但考虑到时间、效率等因素，实验中需尽可能提高气压。     

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。     

近距治疗的新进展

简要回顾了放射治疗的发展史。从治疗设备、核素选择、制源技术和照射技术四个方面阐述了近距治疗在近年来国内外取得的进展,并对其前景作了预测。     

Recent Developments in Magnetron Sputtering

The principle of magnetron sputtering is introduced andthe balanced and unbalanced magnetrons are compared andthe necessity of unbalanced magnetrons is explained as well. Several recent developments in plasma magnetron sputtering, i.e., unbalanced magnetron sputtering, pulsed magnetron sputtering and ion assisted sputtering, are discussed. The recent developments of unbalanced magnetron systems and their incorporation with ion sources result in an understanding in growingimportance of the magnetron sputtering technology, which makes the technology an applicable deposition process for a variety of important films, such as wear-resistant films and decorative films.     

Recent Advances in Gas Scintillation Proportional Counters

Various geometrical configurations for gas scintillation proportional counters have been investigated in order to determine which is best for use in a large volume, high efficiency counter for measuring low energy gamma and x-rays. A xenon filled counter having a rod anode inside a cylindrical cathode appears to provide the best configuration for providing a uniform field and the best resolution over the total volume of the counter. The details of construction and operating characteristics of various shaped counters are described.     

Recent Developments in Nuclear Medicine Instrumentation

Nuclear Medicine instrumentation, as is the case for most sophisticated technologies, is constantly being improved through the introduction of new devices as well as through refinements in devices that are available from several manufacturers. The purpose of this text is to describe the recent developments that have led to improvements in the performance of instruments currently being used for routine diagnostic studies and to also describe some of the new devices that are becoming available.     

Recent Developments in Air Particulate Monitoring

During the past 50 years, man has become acutely aware of the air pollution pervading our environment. Thus he has focused a considerable amount of scientific study on the chemical and physical properties of gaseous and particulate contaminants. A key element in the classification of particulate pollution is the sampling procedure used to collect particles, with the emphasis on separating the respirable from the non-respirable fraction. Generally, impaction techniques have been utilized for size collection of particulates, but these procedures can be affected by the nature of the impaction collection technique which can cause the particles to bounce from one stage to the next, particularly when larger sample quantities are desired for chemical analysis and gravimetrics. Recently EPA, working with several other investigators, perfected a dichotomous collection device, based on virtual impaction principles, which separates and collects particles into two size ranges, 0 to 3.5 microns and 3.5 to 20 microns. Particle bounce at the collection surface is not a problem with this sampler because particles are captured by filtration. The operation and design of manual and automated virtual impactors are discussed. In addition, the application of x-ray fluorescence to the analysis of particulates collected with the dichotomous sampler is described.     

Development of Position Sensitive Helium-3 Proportional Counter for Thermal Neutrons with Novel Signal Readout

A position sensitive ³He proportional counter for thermal neutrons with a novel signal read- out method which has two pre-amplifiers at only one end of the counter body has been developed. It has an advantage for usage in a special environment, such as in a subcritical facility or in water, or for insertion into a narrow space. The characteristics of the counter were evaluated with thermal neutrons. The position resolution was 7 mm with an effective length of 1,200 mm. The integral non-linearity of position signal was less than 0.5%.     

Recent Waste Management Related Developments in Germany

The Federal Republic of Germany intends to dispose of all types of radioactive waste in deep geological formations. This waste comprises spent fuel elements, vitrified fission products, nuclear power plant operational and decommissioning waste as well as spent sealed radiation sources and miscellaneous waste originating from small waste generators. The Federal Government made a pronounced change in energy policy since 1998, the most important feature of which is the abandoning or phasing out of nuclear energy, finally set in force by the April 2002 amendment of the Atomic Energy Act. According to the new approach to waste management and disposal, further sites in various host rocks shall be investigated for their suitability. A special expert group was set up to develop repository site selection criteria and respective procedures on a scientifically sound basis. The objective of the site selection procedure is to identify—with public participation—potential disposal sites in a comprehensible and reliable way. Step by step and based on the said criteria, those areas, site regions and eventually sites shall be selected, which offer particularly favourable conditions for the later demonstration of the final site's suitability and its confirmation in a licensing procedure.     

Recent Developments in Accelerator Based Atomic Physics

Much progress toward a detailed understanding of atomic collision phenomena and atomic structure has recently been made with the aid of accelerated ion beams. Beam foil Lamb shift measurements and the possible observation of spontaneously created positrons from quasi-superheavy atoms give promise for critical tests of QED. The mechanisms of innershell ionization and charge transfer in ion atom collisions have been intensively investigated and the results have brought together the various approaches - Coulomb excitation and MO treatments for these processes. That violent collisions at high energies can cause multiple ionization of the target atom has been known for some time. However, only recently have theoretical treatments been able to predict, e.g., the degree of L shell ionization accompanying K shell ionization. The highly charged ions formed in these collisions have themselves come under intensive investigation and are used for the study of the structure and collision physics of multiply charged species. Electron-Ion collision studies have also been started and initial results on dielectronic recombination are reported.     

Recent Developments in Heavy Ion Beam Probe Diagnostics

Heavy Ion Beam Probe diagnostic (HIBP) is a non-perturbative local multipurpose diagnostics that allows us to monitor the temporal evolution of 2D distributions of several plasma parameters, such as the electric potential Φ, the density n, the poloidal field B_p and the electron temperature T_e. HIBP allows us to measure the fluctuations Φ, B_p and n, which may cause the anomalous transport. The investigation of the plasma electric potential can be provided by HIBP only.