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The photodisintegration of deuterium ( Q = −2.22 MeV ) in combination with a neutron counter has been used to detect high-energy γ-rays. The γ-ray source is surrounded by a tank filled with heavy water and the emitted neutrons are counted in 4π geometry with neutron detectors embedded in a graphite moderator. The absolute detection efficiency of a small test system (1.8 1 D 2 O) has been determined for E γ = 2.6–8.1 MeV and found to agree well with calculations (e.g., 8.0 × 10 −5 at E γ = 4.4 MeV). It is proposed that the system should be useful for the study of capture reactions induced on highly radioactive targets. Improvements in detection efficiency as well as limitations in data analyses are discussed.

For many applications it is necessary to measure the three coordinates of a stopped gamma ray. A method for making such a measurement for a scintillation gamma ray detector is described. Factors affecting the gamma ray detection efficiency are discussed as well as methods to be used in fabricating the detector.

The design and performance of NaI(Tl) - CsI(Na) phoswich detectors for X-ray Astronomy applications are presented. Phoswich techniques enable the design of low-background, actively-shielded detectors of large sensitive area, while maintaining minimum weight and cost. Results from a balloon-borne test flight incorporating several detectors, including one with an effective area of 765 cm2, are discussed.

The efficiency of metal converters is investigated. A simple method for the evaluation of conversion efficiency is given. The optimal thickness of converter plate was found experimentally. The design of two types of high-energy converters is described and an application to X- and γ-ray detectors is suggested.

An efficiency optimized single photon tomographic system, GAMMATOM-1, is developed and its performance is studied. The system consists of 36 NaI(Tl) crystals of 2cm (diameter) × 3.8cm (length) arranged in a circular form with four banks or arcs (each arc with 9 NaI(Tl) crystals). Resolution of 7mm fwhm is obtained with a 16cm diameter resolution-phantom of 99mTc. Sensitivity of the system has also been measured and obtained 10K ~ 15K (counts/sec) / (?Ci/cc) with a 20cm diameter uniform circular phantom of 99mTc. System design details and performance are reported.

X-ray fluorescence from lead when irradiated by gamma rays from a Co-57 source was utilized to measure the lead concentration in children's teeth in situ. The sensitivity of the method was adequate to detect 15 PPM from a gamma ray exposure to the tooth approximately 1/10 the exposure of a routine dental x-ray examination. The tooth lead levels assayed using x-ray fluorescence correlated well with chemical assay techniques for both extracted permanent and shed primary teeth. Thirty children from the Children's Hospital of Philadelphia suspected of having elevated lead levels had tooth lead levels measured in situ determined using the x-ray fluorescent technique. The tooth lead concentration varied from a low of 16 PPM to a high of 56 PPM.

A beam loss detection system employing self-powered gamma detectors to monitor the radiation produced by stray beam has been installed on the 35 MeV linac. The system enables the operator to optimize machine and beam transport parameters to a precision not possible using conventional monitors alone.

The application of nuclear engineering discussed in this paper relates to digital processing of images formed by the detection of gamma radiation retained in various organs in the body after the injection of radio-pharmaceuticals. These images are presented in a color photograph display to aid diagnosis and minimize system artifacts.

A preliminary study has been carried out to establish the usefulness of a simple clinical technique for evaluating the relative cerebral blood flow in each hemisphere. The theory of the test is to monitor the arrival in the head of intravenously injected radioisotope. Two collimated detectors monitor the two cerebral hemispheres for 60 seconds. The test is simple to administer and extremely safe since a rapidly excreted radioisotope is used. Preliminary study suggests it may be of considerable clinical value in view of its simplicity and safety.

For measurements of neutron spectra by the time-of-flight method, calculations and analysis of the detection efficiency of the captured gamma rays in a system consisting of a central detector surrounded by four NaI(Tl) crystals were carried out. The central detector of cylindrical shape contains a homogeneous mixture of 10B with polyethylene of different thickness and/or a 1.5 cm thick layer of boric carbide. The gamma ray detection probabilities as functions of the position of neutron capture are calculated by the Monte Carlo method.

An evaluation of a 26.3% relative efficiency Ge(Li) detector for low-level radionuclide analysis has been made. The detector performance for sources mounted at the detector end cap was compared with the other smaller Ge(Li) detectors and with an opposed Ge(Li) two detector system. Factors studied included resolution, peak-to-Compton ratios, background, detection efficiency at the end cap, source geometry, and relative sensitivity. The 26.3% relative efficiency detector was found to give superior end cap efficiencies, peak-to-Compton ratios, and relative sensitivities without sacrificing performance in the other factors studied.

The problem of measuring gamma activity at the natural levels, particularly in people and foodstuffs, is an extremely important one because of the necessity of monitoring both fallout from nuclear weapons tests and the disposal of reactor wastes. This problem will also be encountered because of the necessity for minimizing radiation in clinical and industrial tracer applications. Two principal techniques have been developed for this purpose which are applicable to in vivo studies: the NaI crystal spectrometer in a special, low-activity shield, and the large 4? liquid scintillation counter. Both have sensitivities which permit the detection of gamma activity in the human body at levels a factor of 10 to 100 below the natural K-40 concentration. The choice between the two systems depends largely on the particular application, since they are comparable in terms of ultimate sensitivity and cost. The liquid scintillator is the method of choice used for routine studies involving large numbers of samples in which the identity of the activity is known. This is the case, for example, in studies of the gamma activity of people and foodstuffs due to fallout because of the large discrimination factors in biological systems against elements not closely resembling nutritional essentials. Natural K-40 and Cs-137 are normally the only gamma activities present, and the energy resolution of the liquid scintillator permits their simultaneous determination. Because of the constancy and predictability of the K-40 level, additional hard gamma activity (e.g.

The environmental level gamma energy system developed at Atlantic Richfield Hanford Company laboratories consists of a single, large volume Ge(Li) detector with an NaI(Tl) anticoincidence guard, all operating in a laminar flow "Clean Room." A peak height to Compton edge ratio of better than 250:1, together with a reducing background, enables analysis of sample volumes from point sources to 700 cc.

Ce dispositif est réalisé par association d'éléments standards. L'adjonction d'une mémoire tampon permet de l'utiliser pour un enregistrement de longue durée à faible taux de comptage.

An attempt to quantitatively calculate the time resolutions from different combinations of Ge gamma-ray detectors, filters, and time pick-off techniques, is described. The study is based on charge collection time calculations previously studied, optimizations of filters, and the choice of parameters in the different time pick-off techniques. Results of the time resolution simulations with a 3 cc planar detector and a 5.6 cc coaxial detector of the Ge (Li) type, are presented and are in good agreement with previously obtained experimental and theoretical results. A brief discussion of the most common trigger modes (and related time jitters and time walks) particularly in reference to the Ge gamma-ray detectors, is also given.

Very simple radiation monitors can be constructed using only a cadmium sulphide cell, a battery and a microammeter. The construction of a versatile prototype unit is described, together with the development of monitors for detecting the transfer of radioactivity in radiochemical processes and portable ratemeters for localizing millicurie quantities in vivo. The limitations of the direct current use of CdS cells are discussed and some further applications within these limitations are listed.

The behavior of many germanium crystals during lithium-ion drift, in terms of compensated depth W as a function of drift time t, does not follow the prediction of the equation: W = (2?LiVt)1/2 Modification of the lithiim velocity expression to include the loss of mobile lithium ions during drift yields the expression: W = [?LiV?(1-e-2t/?)]1/2 which seems to describe satisfactorily the experimental results. In addition to the loss mechanism, the effect of oxygen on lithium-ion drift mobility is considered.

The total efficiency of γ-ray detection by Ge(Li) semiconductors is calculated for the energy range 0.1 to 10 MeV, for cylindrical detectors with radii from 0.25 cm to 2.5 cm and thicknesses from 0.1 cm to 1 cm, at distances between the source and detector ranging from 2 cm to 20 cm.

Dans cette Note on trouvera la description d'une pile haute tension du type Zamboni. Cette pile est destinee a alimenter certains appareils portatifs electroniques de faible consommation. La fabrication d'une telle pile et les principaux facteurs intervenant dans son fonctionnement sont indiques. Quelques applications recemrnent realisees sont citees a la fin de la Note.

This paper discusses selected instrumentation and control experience from the startup of Oconee I which is an 886 MWe nuclear generating and first-of-a-kind design.

This article possibly does not contain any new information. Neither is it a condemnation of gamma ray spectrometry or the use of large radiation crystals. It is intended to examine gamma ray detection comparing total count and spectrometry in several applications. metry in several applications.

The gamma ray detection efficiencies of off center points on the surface of a Ge(Li) detector, of a cylindrical single open ended (SOE) type, were measured relative to the efficiency of the center of the detector. The radial dependence of the efficiency e(r) can be approximated quite satisfactorily by the equation ϵ(r) = e0 exp (— Br2), were e0 is the efficiency at the center of the detector and B is a constant characteristic of the detector and the energy of the γ rays.

Thick target yields for the reaction 6Li(d, nγ)7 Be have been measured using LiF and LiCl targets at deuteron bombarding energies between 48 and 170 keV. Assuming recently published values for the stopping powers of deuterons in Li and F, the LiF thick target yields were used to deduce the total cross section for the reaction, 6Li(d, nγ)7 Be. The cross section varies from about 0.3 mb at 160 keV to about .004 mb at 60 keV. A comparison between the yields measured used the LiF and LiCl targets allowed a measurement of the relative stopping powers of deuterons in F and Cl. A significant discrepancy is observed between our measured values of the relative stopping powers and the predicted value of the relative stopping powers based on recently published values.

Several successful experiments carried out with the scintillation chamber are summarized to show what can be done with the systems which can be built now. There have been no developments in scintillation chamber components in the last year which allow radical improvements of these present systems. Many of the high energy nuclear experiments envisaged for the scintillation chamber can be done better with spark chambers. As a result of these two factors, there are only a few areas where a scintillation chamber is now the best instrument to use. Examples of such areas are space physics experiments, high energy beam imaging, high energy gamma ray detection and particle decays.

Étude et réalisation d'un préamplificateur de charge à très faible bruit utilisant un transistor à effet de champ refroidi, associé à un détecteur gamma au germanium.

The use of Avalanche PhotoDiodes (APD) coupled to fast inorganic scintillators is evaluated for possible applications in medical systems. Several tests have been done on different configurations built coupling commercially available APD with scintillators like YAP and GSO. Experimental evaluation of performances like energy range, energy and time resolutions has been obtained. Starting from these results Monte Carlo simulations have been carried out to model a multi-element detector designed for possible PET applications. Some quality factors have been defined to compare the characteristics of the different single detectors tested. The Monte Carlo results are also used, in a feedback process, to optimize the use of the single element of the arrays.

A compact wavelength-shifting fibre (WSF) gamma camera for 140 keV gamma rays has been developed and an evaluation of its performance is presented and discussed. A spatial resolution of 4 mm FWHM was achieved which is comparable to that of modern Anger cameras. Simulation results predict a spatial resolution better than 3 mm if the WSF signals are 3 times higher than those obtained experimentally ways of achieving this goal are discussed.

In past years, liquid rare gas detectors (LRGD) have made a considerable progress and found application in various fields of research, such as high energy experiments, astrophysics, search for rare processes and medical imaging. This review paper starts by a short summary and discussion of the properties of liquid rare gases (LRG) that make them attractive as radiation detector media. Next, the two best-established technologies based on liquid rare gases, electromagnetic calorimeters and time projection chambers, are briefly reviewed along with their main applications. The bulk of the paper is focused on the challenging development of LRGD for the search of rare processes in low background experiments with an emphasis on those dealing with the direct detection of dark matter. The challenges posed by those experiments, the detectors proposed and their present status of development are described. A brief review of the proposals of using LRGD for medical imaging is outlined and the present status of some of the more significant developments under way is presented.

The measurement of the scintillation efficiency for xenon nuclear recoils relative to that for 122 keV /spl gamma/-rays is reported in the energy range from 5 keV to 140 keV. Prior to those measurements, the performance of the chamber with respect to the light collection efficiency, energy, time and position resolutions was assessed using 122 keV and 511 keV /spl gamma/-rays.

The use of dedicated gamma camera, with high intrinsic spatial resolution can raise the detection of sub centimeter cancers in Scintimammography. The recent development of new gamma imagers based on scintillation array with high spatial resolution has strongly improved the SNR of the resulting images; however, Compton scattering contamination is the main drawback in Scintimammography, since it limits the sensitivity of tumor detection, especially in the portion of the breast close to the chest. In this paper we introduce the multivariate image analysis as a numerical technique to improve the tumor detection and tissue identification in scintimammographic imaging. The total pulse height distribution resulting from the detector is considered as series of images viewing the same field-of-view. The stack of images resulting from different intervals of the photon spectra is a multivariate image and can be studied by the principal image component analysis. This method is shown as a two-step procedure: calculation of loadings and calculation of scores. Scores can be shown visually and by the global pixel correlation and anticorrelation the contribution of chest, healthy tissues, and tumor can be highlighted. The results show the realistic possibility to depict scintimammographic images as a series of principal components images that are able to separate Compton contamination, improving the visibility of breast regions with higher Tc/sup 99m/ Sestamibi uptake.

By applying the multiple gamma ray detection method to PGA, the interference from strong gamma ray can be reduced, therefore quantification limits of trace elements are improved significantly. MPGA detector system is constructed at the guide‐hall of JRR‐3M in JAERI. Several standard samples were measured by MPGA detector system.

There is an experimental gap in the study of the non-thermal universe in the photon energy range from 0.3 to 100 MeV. We have analyzed the performance of a detector with unprecedented sensitivity, angular and energy resolution and combined with polarimetric capability to study of the most powerful Galactic and extragalactic sources and with a line sensitivity in the MeV energy range two orders of magnitude better than previous generation of instruments that can determine the origin of key isotopes fundamental for the understanding of supernova explosion and the chemical evolution of our Galaxy.

BeppoSAX detected a few GRBs with both the GRB Monitor and the Wide Field Cameras. Fast follow-up observation of the field with Narrow Field Instruments of SAX and with other X-ray telescopes has allowed for the detection and monitoring of the GRB afterglows. We discuss the temporal behaviour of the two events better studied both in the whole band and in the band where the Narrow Field Instruments and the Wide Field Cameras overlap.

The measurement control complex for detection and identification of radioactive and fissile materials which is developed in MEPhl and based on passive method of their detection is presented. Characteristics of multilayer /sup 3/He neutron and xenon gamma-ray detectors as well as information on systems of assembling and processing the data are described.

The AGILE scientific instrument is based on an innovative design based on three detecting systems: (1) a Silicon Tracker, (2) a Mini-Calorimeter, and (3) an ultralight coded mask system with Si-detectors (Super-AGILE). AGILE is designed to provide: (1) excellent imaging in the energy bands 30 MeV–50 GeV (5–10 arcmin for intense sources) and 10–40 keV (1–3 arcmin); (2) optimal timing capabilities, with independent readout systems and minimal deadtimes for the Silicon tracker, Super-AGILE and Mini-Calorimeter; (3) large fields of view for the gamma-ray imaging detector (∼3 sr) and Super-AGILE (∼1 sr).

Prompted by recent interest in positron emission tomography scanners equipped with LuAP:Ce (LuAlO/sub 3/:Ce) scintillators read by avalanche photodiodes, we have measured timing properties of this scintillating material with large-area avalanche photodiodes (LAAPDs) from Advanced Photonix, Inc. (API). We have obtained a time resolution of 1.16/spl plusmn/0.06 ns for 511 keV peak from a /sup 22/Na source with energy threshold set at 400 keV and 680/spl plusmn/35 ps for /sup 60/Co source with energy threshold set at I MeV. The dependence of time resolution on LAAPD gain was measured showing improved timing at gains over 200, but at the cost of higher excess noise. Comparing the time resolution of LuAP:Ce and LSO:Ce measured with LAAPD and photomultipliers, we discuss the dependence of timing properties on the tight output and decay time of these scintillators.

A phantom designed for the study of radiologically-contaminated land is described. The phantom comprises a bespoke, 1 m3 outer tank and an inner tube matrix for the deployment of γ-ray emitting radioactive sources. The phantom was filled to a depth of 900mm with dry sandy loam to mimic soils found in areas surrounding nuclear legacy facilities in the U.K. A series of non-intrusive spectral measurements were taken using an automated scanning rig and a cadmium telluride γ-ray detector. The detector was clamped at a constant height above the phantom, face-down and sequenced over a pre-defined grid above the phantom, using a scanning rig. A small caesium-137 source was positioned at a depth of 150mm in one of the tubes at random. Scans were then conducted at 30 minute intervals at twelve separate measurement points, to allow sufficient counting time to isolate the γ-ray caesium-137 662 keV photopeak from the background. A CAD model was then built of a simplified albeit geometrically correct representation of the phantom and the reading points. The combination of this model and the imported γ-ray spectra has enabled the inverse modelling technique N-Visage™ to be validated against the accurate surface location for the source without prior knowledge.