摘要:

Three new and important lines of development in nuclear radiation detection and measurement occupied the major part of the presentations and discussions of the first two days of the Conference. Two of these developments, spark chambers and image-intensifier/luminescent-chamber systems, enable pictures or other records of nuclear particle tracks to be obtained with a much higher degree of time resolution than is possible with existing techniques, e.g. with cloud chambers or bubble chambers. This is an important step forward in measurement techniques for the study of rare processes in nuclear reactions, in the presence of large-particle fluxes or of other interfering reactions. Image intensifiers might also be used for observation of Čerenkov radiation and the determination of particle velocities. Measurement of the Čerenkov angle, i.e. the angle between a particle path and the direction of emission of its associated Čerenkov radiation, is the only method applicable for accurate measurement of velocity for particles travelling at speeds within 0.1% of the speed of light. A third topic of importance was developments in the design and use of semiconductor nuclear-particle detectors. The present report gives an outline of the main principles of these methods of measurement with a summary of device techniques and characteristics and their application to nuclear radiation measurement, as exemplified by the Conference papers. A brief survey is also given of papers dealing with other miscellaneous topics relating to scintillation and gasionization radiation detectors.

DOI:10.1049/pi-b-2.1962.0218

出版商:IEE    

年代:1962

数据来源: IET

摘要:

This is a report on the papers presented at the International Atomic Energy Agency Conference on Nuclear Electronics in the field of radiation monitors and instruments which was held at Belgrade in May, 1961. The report deals particularly with contamination monitors, survey (dose-rate) meters and instruments for monitoring gaseous and liquid effluent for radioactive contamination. Among the new techniques mentioned are the following: selective γ-monitoring for portable instruments; the use of semiconductor devices as radiation detectors; impactors for sorting particulate contamination according to the size of the particles; alarm systems taking account of normal natural background variations, so that more rapid variations automatically operate on alarm; the use of Čerenkov detectors in liquid effluent monitoring; the monitoring of surface contamination on fuel elements; the use of coincidence scintillation-counter systems for determining the direction of γ-radiation, for source location; and the remote indication of radiation monitors using telephone lines.The report gives details of a number of new instruments, including a new type of personal radiation monitor, and a new type of instrument for detecting accidental reactor excursions, as well as several new types of plutonium monitors.Reference is made in all cases to the original papers, which will shortly be available in the Proceedings of the Belgrade Conference, which will be published by the International Atomic Energy Agency, Vienna.

DOI:10.1049/pi-b-2.1962.0219

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Monitoring for airborne plutonium presents special problems because the physical and biological properties of plutonium are such that the permissible concentration in air is less than the normal background concentration arising from naturally occurring α-emitters. Because of this difficulty it is desirable to examine the basic health-physics requirements, so as to evaluate the usefulness of the limited information which might be available from relatively simple equipment. The now generally accepted concept of averaging dose over a period of 13 weeks or a year or even longer allows considerable flexibility in operational control, so that the immediate indication of small increases in concentration over the normal level, although it may be very desirable, is not essential, and its value must be weighed against such factors as cost, difficulties in use and interpretation, and the potential loss of reliability of a complex instrument.The various instrumental systems which have been suggested may be divided into three broad classes: (a) direct, in which the plutonium and background radioactive particles are collected and measured together, (b) selective, in which an attempt is made to collect only the plutonium dust, and (c) compensative, in which the background and plutonium dusts are collected together but the counting system is designed to remove the counts due to background before readout. There are inherent difficulties in each of these systems, but several prototype instruments have been made which show promise of a considerable measure of success.

DOI:10.1049/pi-b-2.1962.0220

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A comparative study of manganese ferrites containing cadmium and zinc, with and without magnesium additions, was performed in order to estimate the effect of cadmium on square-loop magnetic properties. The preparation of cadmium ferrites is very complicated because of the detrimental cadmium volatilization. This may be reduced by applying high oxygen pressure at peak sintering temperature. Ferrites containing cadmium have relatively lower coercive force than those containing zinc. The gain in magnetic properties is primarily due to crystal growth favoured by the presence of cadmium in the solid-state reaction of oxides.

DOI:10.1049/pi-b-2.1962.0221

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Ferrite-core stores are at present the most suitable high-speed memory system for use in a parallel digital computer. The relevant properties of ferrite memory cores and the way in which they are interconnected and interrogated in a coincident-current core store are reviewed, and some specific limitations are considered.The paper is based on an experimental investigation into the noise voltages which can appear on the sense wire of a coincident-current memory plane using ferrite cores. There are two largely independent types of asymmetry which can occur in a cancelling pair: (a) the information held may be different and (b) the final half-current disturbances may have been in opposite senses. The ‘worst noise’ condition arises when (a) and (b) are present together in such a way that their effects add. Means by which this pattern can occur in a practical memory are discussed, and waveforms are presented to illustrate the phenomena. A ‘post-write-disturb’ pulse, staggered read currents and a split sense wire can reduce the noise by ten to one. A rectangular sense-wire threading can largely eliminate the shock-excited decaying oscillations produced by stray couplings.

DOI:10.1049/pi-b-2.1962.0222

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Measurements of the amplitude-probability distributions of atmospheric noise in a power bandwidth of 370c/s, made at the Radio Research Station, Slough, England, during the International Geophysical Year, are presented for frequencies of 24kc/s, 135kc/s, 11Mc/s and 20Mc/s. The diurnal and seasonal variations of the noise power and average value of the noise envelope are derived, and a comparison is made between the measured noise power and predictions prepared under the auspices of the International Radio Consultative Committee (C.C.I.R.).The distributions are normalized to the r.m.s. level and summarized in representative curves. The variations of these composite distributions are expressed in statistical terms, with particlar reference to the r.m.s. to average ratio and the overall dynamic range.

DOI:10.1049/pi-b-2.1962.0224

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A travelling-wave parametric amplifier has been constructed in the h.f. band with the object of comparing theory and experiment. The signal line is a low-pass filter in which the shunt elements are similar varactor diodes. The pump is coupled into each diode from a high-pass filter pump line.Gain, bandwidth and noise factor have been studied under diverse conditions. These include matched terminations, mismatch at the load and mismatch at both source and load. In the latter case the possibility of regenerative reflections arises. The signal gain is of the order of 10dB, the bandwidth is approximately 3 Mc/s and the double-channel noise factor is less than 1.1 at midband (6.7 Mc/s).

DOI:10.1049/pi-b-2.1962.0225

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A description is given of the construction and the method of operation of the rotary attenuator, and it is shown that, since the measurement of attenuation by this instrument is dependent inherently upon the measurement of an angle, it is an absolute device. By the use of scattering coefficients and considering the various discontinuities within the instrument, the errors that can arise in its use are analysed. It is shown that the most serious source of error is due to insufficient maximum attenuation, which can be due to a limitation of the centre vane or to misalignment between the end vanes. All other errors can be measured and made negligible by good microwave measuring practice.Finally, some details are given of the methods that can be used to check the law of the attenuator and practical accuracies, and results are presented for an instrument operating in the 3 cm waveband which has been compared with a precision piston attenuator operating at 60 Mc/s.

DOI:10.1049/pi-b-2.1962.0227

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A method is given by which resonance-absorption isolators may be designed to handle any required mean power level and load mismatch without deterioration in performance. The method is derived from a study of the properties of small discs of ferrite in X-band waveguide at high mean powers and of the thermal conditions in the ferrite. It requires the proper choice of the shape demagnetizing factors in the isolator, together with a knowledge of the maximum temperature at which the ferrite may usefully be operated at gyromagnetic resonance.Practical limits to power handling by this method are discussed, and the relative degrees of usefulness of the various materials measured for this application are presented in terms of their maximum operating temperatures.Typical performance data are given of resonance isolators in the X-band, which will handle mean forward powers of over 2 kW with a 25% load reflection, whilst maintaining their low-power characteristics.

DOI:10.1049/pi-b-2.1962.0228

出版商:IEE    

年代:1962

数据来源: IET