Gamma-ray Pulse-height Spectra Research Articles

VAXGAP: a code for the routine analysis of gamma-ray pulse-height spectra on a VAX computer

VAXGAP (VAX Gamma-ray Analysis Package) is a collection of computer programs for the analysis of pulse height spectra acquired on Ge detector-based spectrometers. VAXGAP was written to provide the operators of a radiation measurements laboratory with the necessary software tools for routine analysis of radioactive samples through the analysis of gamma-ray pulse-height spectra. The authors summarize the unique features and the organization of VAXGAP which makes it of particular value in the routine analysis of spectra.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The Use of a Small Accelerator as a Source of 14-MeV Neutrons for Shielding Studies

It is important in calculating complex shields such as those proposed for the fusion reactors to ascertain that the neutron cross-section data sets used in the calculations are as accurate as possible and that the calculational methods used to transport the neutrons are as reliable as practical. To assure that both these criteria are met, a project at the Oak Ridge National Laboratory (ORNL) is being conducted in which a small accelerator is used to provide 14-MeV neutrons via the T(d, n)4He reaction and an NE-213 detector is used to measure the neutron and gamma-ray pulse-height spectra of the radiations transported through and/or created in very thick laminated shields of stainless steel (type 304) and borated polyethylene. To produce the neutron flux required, the targets are made by depositing about 4 mg/cm2 of TiT onto a 1.27-cm circular area of a O.254-cm thick copper disk. The NE-213 detector is operated in standard, state-of-the-art electronic circuits. A surface-barrier alpha counter and a small NE-213 detector are located permanently at a distance of about 150 cm from the target to monitor the reaction rate in the target. The pulse-height data are unfolded to produce energy spectra by using the computer program FERD. These results are then compared almost immediately with spectra obtained using two-dimensional radiation transport methods incorporating 53-neutron, 21-gamma-ray energy-group cross section data derived from the VITAMIN-C data set (ENDF/B). Laminated stainless-steel and borated polyethylene shields having thicknesses up to 412 g/cm2 have been measured.

A small rugged imaging X-ray spectrometer: A lixiscope with good energy resolution

A new prototype Lixiscope (Low Intensity X-ray Imaging Scope) is described for operation in the 20–200 keV region. In addition to good spatial resolution, the new prototype is capable of providing simultaneous gamma-ray or X-ray single-photon counting, imaging, and energy resolution. The observed energy resolution determined from gamma-ray pulse-height spectra is only a factor of two poorer than that of a NAI(T1)-PMT (photomultipler tube) system. Taking into account the good spatial resolution, such a Lixiscope is thus equivalent to operating thousands of NaI(T1)-PMT systems in parallel with minimal degradation in overall energy resolution. These characteristics make the new prototype Lixiscope a compact and rugged device eminently suited for possible low-flux imaging applications.

Gamma ray intensity standards for calibrating Ge(Li) detectors for the energy range 200–1700 keV

Gamma ray pulse height spectra for seven radioactive sources have been analyzed for the full energy peak areas. Using these areas in conjunction with the results of an extensive compilation of relative gamma ray intensities, a relatively simple efficiency function has been used to calibrate a coaxial Ge(Li) detector. The resulting relative intensities for each source have been used in investigating the consistency of the weighted averages of the compiled relative intensities. Possible systematic errors are discussed and recommendations are made with respect to the choice of gamma ray intensity standards.

Calculation of gamma-ray pulse height spectrum in a semiconductor detector in the presence of charge carrier trapping

An integral expression for the spectral distribution produced by monoenergetic gamma rays on a planar semiconductor radiation detector has been derived. The effect of the charge collection efficiency has been included by using the Hecht relation for mobile holes and electrons. The method of subtracting fwhm contributions by quadrature when attempting to separate the contribution produced by finite drift lengths from effects such as the electronic noise, pair creation statistics, material inhomogeneities, or other independent processes can be grossly in error. A FORTRAN program to numerically evaluate the integral and calculate a spectrum is included.

Low energy gamma radiation in the atmosphere during active and quiet periods on the Sun

Gamma ray pulse height spectra during active and quiet solar periods from midlatitude balloon flights

Multiple linear regression analysis of scintillation gamma-ray spectra: Automatic candidate selection

Multiple linear regression (MLR) has been shown to be a quantitative and statiscally justifiable method for unfolding scintillation gamma-ray pulse-height spectra of radionuclide mixtures. The principal requirements of the method are:(1) that well-calibrated data are used, and (2) that candidate set of spectra (standard spectra to be used as regression variables) must be complete and exclusive. In the usual application of the MLR method, the user exercises a great deal of subjective (irreproducible) judgment in the selection of a candidate set. Several algorithms have been proposed for automatic candidate selection but are not completely justifiable on the basis of proper statistical procedures. In this report, an algorithm is described in which justifiable statistical procedures are used. Correlation coefficients are examined to determine the proper candidate set for a given experimental spectrum. The inclusion or exclusion of candidate spectra are justified on the basis of valid statistical indicators, and an estimate of the goodness of the final fit is provided. The results of unfolding actual experimental spectra by this method are included in the paper.

Internal Energy Standardization of Multichannel Gamma Ray Spectra by Use of the 0.511 MeV Annihilation and 40K Peaks

A computer method is described for making after-the-fact adjustments for incorrect zero energy intercept and instrumental gain to experimental gamma ray pulse height spectra from NaI (Tl) scintillation spectrometers. The method makes use of the 0.511 MeV annihilation peak and 1.46 MeV 40K photopeak as internal energy reference standards, both of which peaks are available to NaI (Tl) scintillation detectors. The technique has been tested experimentally and appears to be of practical use for routine energy standardization of long counting time gamma ray spectra between 0.1 and 2.0 MeV.

A simple high resolution pulse shape discriminator

A pulse shape discrimination syste the following characteristicsm high nultiparticle resolution ( M≈3), wide dynamic range (1< E n<30 MeV), simplicity, passiveness. stability, high-count-rate capability (> 50kHz), built-in calibration, minimum weight (<20g) and low power consumption. This system simultaneously extracts the separate gamma-ray and neutron pulse height spectra. NEe sample data presented were obtained with NE213 liquid scintillator,, RCA 8575 photomultipliers and two-phrameter pulse height analyzers.

Gamma-ray pulse-height spectra: Formation of a response matrix for iterative unfolding

One method for obtaining gamma-ray spectra is the application of the iterative unfolding technique to the measured pulse-height spectra. This technique, however, requires the construction of a response matrix which contains a series of response functions of the detector assembly to various gamma-ray energies. This report describes the essential steps in the construction of a response matrix, having the dimensions 100 energy bins and 1024 channels, used to obtain the complex gamm-ray spectra from the experimental pulse-height spectra. The photons of interest have an energy range extending from 0.060 to 5.00 MeV. The report also presents the associated computer programs for generating and using the response matrix. The results of unfolding of synthesized pulse-height spectra having a known number of gamma rays of known energy are presented. The computer programs are written in Fortran II language for use with an IBM-704 computer.

Unfolding time-dependent gamma-ray pulse height spectra by vector analysis

A vector analysis approach is suggested to unfold time-dependent gamma-ray pulse height spectra.

Least-squares analysis of time-dependent gamma-ray pulse-height spectra

In this report a computer method is described for estimating radionuclide abundances in a mixture by least squares analysis of a time-dependent set of gamma-ray pulse-height spectra. The pulse-height distributions and decay constants of the constituent radionuclides are used as known input information. The method was programmed for the computer and the program was tested by analyzing spectra of mixtures of103Ru and106Ru of known compositions, whose103Ru fractions varied from 10% to 90%. The mixture compositions were determined by this program with an accuracy of better than 2% of the actual amount, and in most cases better than 1%.

A method for the analysis of pulse height spectra

An analytic method for computer analysis of gamma-ray pulse-height spectra is discussed and some results of the computer program are presented. The method allows the determination by the computer of the number and energies of the constituent gamma rays as well as their relative intensities

A method for the analysis of pulse height spectra

An analytic method for computer analysis of gamma-ray pulseheight spectra is discussed and some results of the computer program are presented. The method allows the determination by the computer of the number and energies of the constituent gamma rays as well as their relative intensities.

Computer correction for shifts in gain and baseline in gamma-ray scintillation pulse height spectra

In the quantitative analysis of multicomponent pulse height spectral data, precision depends upon 1. the statistical variation inherent in the radioactive decay process, 2. statistical variations in the detection process and 3. instrumental variations. The nature of the statistical variations in categories 1 and 2 are well understood and easily considered in the estimation problem. Category 3 variations are more difficult to evaluate and correct. The main variations observed in this category are of gain and baseline. In order to determine the instrumental conditions that prevail at the time of measurement, the spectrum of a standard ( 44Ti) was obtained immediately before experimental spectra were obtained. This standard spectrum was then compared to a reference standard spectrum to obtain estimates of gain and baseline status, and appropriate corrections were applied to the experimental data. This technique, which can correct for shifts in both baseline and gain in excess of one channel (with respect to channel 256 of a 256-channel system), is capable of making corrections of as little as 1 20 of a channel. Improvement in the resultant quantitative estimation of the constituents of multicomponent pulse height spectra is demonstrated. The method should provide the basis of a good quality control procedure for the scintillation gamma spectrometer, provided the spectrometer data can be conveniently entered into a computer.

An analytical method of analysing gamma-ray pulse height spectra

Abstract An analytical method for the conversion of count rate distribution due to gamma-rays to the true incident photon spectrum by means of a “sensitivity matrix” has been discussed. The method of determining the sensitivity matrix by using radioactive gamma ray sources and its correctness regarding intensity and energy reproduction for various gamma ray spectra is described. Finally the limitations of the method are discussed.