Height Analysis Techniques Research Articles

Development of gamma-ray diagnostics for ITER

Gamma-ray spectrometry is a diagnostic tool for fast ions in large tokamak plasmas. The information provided allows us to identify and simultaneously distinguish the presence of fast α-particles and other ions (H, D, T, 3He) to obtain information on their energy distribution and relative densities, in addition to performing a tomographic radial profile reconstruction of the γ-emission sources. The lack of vertical diagnostic ports in ITER makes the implementation of tomographic neutron and γ-ray systems more complicated. The use of a vertical divertor port for the implementation of a vertical viewpoint is currently suggested. The strong magnetic field (∼2 T) found there makes it hard to use conventional multi-dynode photomultipliers as light detectors. Instead, the use of micro-channel plate photomultipliers is suggested here. Investigations of the magnetic field impact on the performance of the γ-spectrometer with a micro-channel photomultiplier are carried out. A high-speed pulse height analysis technique, which allows us to trace gain changes in the photomultiplier tube, is developed at the Ioffe Institute. The tests demonstrate the feasibility of γ-spectrometric measurements in the divertor port provided that micro-channel photomultiplier detectors and the developed high-speed technique are used.

Design and construction of X-ray pulse height analyzer assemblies with radial scanning system for the LHD

A pulse height analysis technique for observing X-rays is planned for Large Helical Device (LHD) plasma experiments to estimate electron temperature and the amount of impurities. The estimation of the nonthermal electrons heated by electron cyclotron heating is also expected. In addition to these primary interests, X-ray observations will be made with a space resolution of better than 10 mm in the radial direction in order to investigate attractive local phenomena occurring in the plasma.

A High Rate NaI Detector System

Front end electronics (detector to ADC) have been developed to operate over an input count rate range of 105 to 106 counts per second with less than ± 1% gain shift and minimal resolution degradation. The system was developed to satisfy requirements for a nuclear hardened gamma densitometer utilizing multichannel analyzer pulse height analysis techniques for reactor background subtraction. The circuitry developed includes a fast current mode preamplifier with first order count rate dependent gain compensation, a baseline restorer, a single channel analyzer with pile-up rejection and live time measuring circuits, and a fast linear gate. The single channel analyzer is used for energy region of interest selection so that only those pulses within the energy region of interest are presented to the analog to digital converter.

Observation of temporal and spatial variations in the Fe/O charge composition of the solar particle event of 4 July, 1974

Comprehensive measurements of the temporal variations of the Z ≥ 6 charge composition in the 4 July 1974 solar event made with experiments aboard IMP-7 and 8 show that large variations in the charge composition occur in three-hour-averaged intensities. Hourly averaged fluxes show variations as large as factors of 3 to 4 from one hour to the next and 3 hour averages show nearly a factor of 10 peak to minimum over the event. The precision of the measurements are limited by counting statistics of the Fe-group channel. Iron to oxygen variations are established by both rate channel and pulse height analysis techniques. Comparison of measurements from IMP-7 and 8, separated by about 70 RE shows that, while significant differences in composition and intensity exist for brief periods, the gross compositional variations are reproduced well at both spacecraft. These observations provide particularly stringent conditions for theories of the acceleration, release, and propagation of solar energetic particles.

Large Area Double Scattering Telescope for Balloon-Borne Studies of Neutrons and Gamma Rays

A large area (1 m × 1 m) double scattering telescope1 for balloon-borne research will be described here. It measures the flux, energy and direction of 2-100 MeV neutrons and 0.5-30 MeV gamma rays. These measurements are made using time-of-flight and pulse height analysis techniques with two large tanks of mineral oil liquid scintillator. Results from Monte Carlo calculations of the efficiency, energy resolution and angular resolution are presented and the electronics implementation for the processing of 80 photomultiplier tubes signals will be discussed. The detector weighs 800 kg with a large part of this weight being the liquid scintillator (320 kg). It will be flown at 3 mbars for flight durations up to 40 hours. The first flight is planned for Spring, 1975.

Reciprocal (push-pull) effects of morphine on single units in the ventromedian and lateral hypothalamus and influences on other nuclei: with a comment on methadone effects during withdrawal from morphine

The effects of morphine and of its antagonists naloxone and nalorphine on multiple single units recorded simultaneously in the ventromedian nucleus (VMN) and in the lateral hypothalamic area (LHA) and certain other neuronal groups were investigated in naive and morphine dependent adult Sprague-Dawley rats using pulse height analysis techniques and computer generated firing frequency histograms. Morphine produced diametrically opposite effects on VMN and LHA in both naive and dependent animals; with the exception of a few units, neurons recorded from the VMN were excited by morphine and, conversely, those in LHA were inhibited; the antagonists naloxone and nalorphine produced clear-cut reversal of these effects. During withdrawal phases in addicted animals, firing rates in the LHA were greater than rates recorded in the same area of naive animals; no significant differences between firing rates in the VMN of naive and addicted animals were observed. Methadone effects were investigated in morphine dependent rats in withdrawal; both VMN and LHA neurons were excited by methadone and the effect of morphine on these nuclei was reversed. The possible implications of these observations for localization of mechanisms in opiate dependency and for the concept of methadone blockade are discussed.

Instrumental Factors and Figure of Merit in the Detection of Low Concentrations by X-Ray Spectrochemical Analysis

Detection of low concentrations in x-ray spectrochemical analysis depends upon the degree of correlation between concentration and spectral line intensity. Various factors causing deviations of points from a calibration curve are mentioned with particular emphasis on deviations due to inadequate spectral resolution and to x-ray counting statistics, both of which are affected by various instrumental parameters. The effects of various choices of instrumental parameters on the counting statistical deviations may be measured in terms of a figure of merit z=A/√ B, where A is the slope of the calibration curve (intensity vs. concentration) and B is the background or intensity at zero concentration. The statistical deviations are inversely proportional to z. Values of z obtained in the analysis of some of the constituents in the NBS low alloy steel standards for several different combinations of instrumental parameters and experimental conditions are presented. It is shown that the use of higher resolution optics or greater dispersion crystals does not always reduce z drastically and in some cases actually increases z The effects on B and hence on z, of spectral purity of the exciting x-ray tube, of pulse height analysis techniques, and of monochromators having no second order reflection, are also examined and are shown to depend upon the spectral nature of B, which in turn depends upon the type of specimen under analysis.

Simultaneous Studies with Fe59 and Cr51 in Congenital Haemolytic Anaemias

SummaryDouble tracer methods using Fe59 and Cr51 for simultaneous clinical investigations of erythropoiesis and red cell destruction are described.In these methods, the clearance of intravenously injected Fe59 from the plasma and its incorporation into the red cells is followed by the assay of blood samples, whilst the turnover of Fe59 by the tissues is followed by body surface counting. At the same time, the survival of Cr51-labelled red cells in the circulating is followed by the assay of blood samples whilst sites of destruction of labelled cells are identified by body surface counting. Pulse height analysis techniques are used for simultaneous measurements of Fe59 and Cr51 both in vitro and in vivo.The use of these techniques is illustrated by results obtained in studies on normal subjects and on patients with various congenital haemolytic anaemias.

Interactions of 38- and 61-Mev Positive Pions in Deuterium

Measurements have been made of the reactions (1) pi /sup +/ + n + p, and (3) at incident pion lab energies of 38 and 61 Mev using a liquid deuterium target and scintillation counters. A separation of the three processes is obtained by determining the mass and energy of reaction products using a pulse- height analysis technique on the signals from the scintillation counters. Results from process (3) are compared with other processes involving two nucleons and a meson and results from processes (1) and (2) are compared with impulse approximation calculations. (auth)

Two-channel gamma counting of Cr 51 and I 131

Red blood cells are easily labelled with Cr 51 and blood plasma is readily tagged with I 131. However, the proximity of the principal gamma energies of these two isotopes complicates the use of differential pulse height analysis techniques for the measurement of doubly labelled blood. Instrumentation for accomplishing this procedure includes a 3 in. well-type scintillation counter operated with two single-channel differential pulse height analyzers. A method is presented for setting up two channels with the analyzers to obtain adequate separation of Cr 51 and I 131. A simple correction for the cross-channel activities is shown. The accuracy of the method is evaluated by the assay of mixed Cr 51 + I 131 sources prepared gravimetrically.