Search Results

You are looking at 1 - 10 of 300 items for :

  • "Gamma ray spectrometry" x
  • Refine by Access: All Content x
Clear All

Abstract  

A new approach is proposed for the measurement of the time-dependent processes in gamma-ray spectrometry. During data acquisition, the energy and the detection time of each event are recorded and the data are later analyzed off-line. This separation of acquisition and data handling extends the possibilities of the analysis. A series of demonstration experiments was performed to show the feasibility of the method, where the half-lives of radioactive isotopes were determined.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors: P. Aarnio, J. Ala-Heikkilä, A. Isolankila, A. Kuusi, M. Moring, M. Nikkinen, T. Siiskonen, H. Toivonen, K. Ungar, and W. Zhang

Abstract  

Linssi is a Structured Query Language (SQL) database for HPGe gamma-ray spectrometry. It covers the whole production chain from sample preparation to final analysis results. Static or mobile sampling and measurement and multiple sample types are supported. In addition, each sample can be split or combined any number of times. A sample may be measured multiple times and each measurement multiply analyzed as well. With Linssi, measurement setups with detectors, shields, attenuators and source geometries can be defined. Full control of calibrations, their histories and tracing of each calibration point back to its corresponding analysis and calibration measurement is supported. Linssi database and user scripts are available from http://linssi.hut.fi/radphys/linssi.

Restricted access

Abstract  

Gamma-ray spectrometry of liquid or finely divided solid samples may be facilitated by incorporating standard activity additions. The count rate rises linearly with added activity, and the intercept and slope of the 1.s.f. line permits the intrinsic activity of the sample to be found. Applications of this method in the determination of210Pb and Th activity are described.

Restricted access

Abstract  

Gamma-ray spectrometry losses through pulse processing dead time and pile-up are best assayed with an external pulse technique. In this work, the virtual pulse generator technique as implemented commercially with the Westphal loss free counting (LFC) module is set up and tested with four high resolution gamma-ray spectrometers. Dual source calibration and decaying source techniques are used in the evaluation of the accuracy of the correction technique. Results demonstrate the reliability of the LFC with a standardized conventional pulse processing system. The accurate correction during high rate counting, including during rapid decay of short lived activities, has been the basis for highly precise determinations in reference materials studies.

Restricted access

Abstract  

GESPECOR is a Monte Carlo based software developed for the computation of efficiency, of matrix effects and of coincidence summing effects in gamma-ray spectrometry. GESPECOR can be applied to coaxial and well-type HPGe or to Ge(Li) detectors and to various types of sources, including point, cylindrical, and spherical sources or Marinelli beakers. In this paper the structure of GESPECOR is presented and the procedures applied are described. The uncertainty of the results computed by GESPECOR is carefully analyzed. The analysis shows that GESPECOR is able to provide results with a well defined uncertainty, in a user friendly WINDOWS environment.

Restricted access

Summary  

A new acquisition and evaluation procedure has been introduced for the measurement of time-dependent processes in gamma-ray spectrometry, in order to extract more information, including half-lives, from the data recorded during acquisition and to enable a more comprehensive analysis of the results. These advanced, off-line data evaluation techniques improve the selectivity and the background subtraction and make it possible to estimate the important analytical parameters (e.g., half-lives) more accurately than with the usual decay curve fitting method.

Restricted access

Abstract  

The spontaneous gamma-rays characteristic of uranium isotopes can be detected and measured in order to identify the isotopic composition of uranium and to assay its total amount in various objects and materials. In order to test these methods of passive gammaray spectrometry in practice, the235U-enrichment of a known fuel rod was determined by counting 186 keV gammas from235U with Ge(Li) detectors of different volumes. The 1001 keV gammas characteristic to238U were counted too. Expected counting rates of 186 keV and 1001 keV gammas for WWER fuels are given and the suitability of passive gamma-ray spectrometry for the determination of235U-enrichment and for the assay of total uranium in reactor fuels are discussed based on these measurements.

Restricted access

Abstract  

Analyses of anthropogenic and natural gamma-ray emitters in the environment require high sensitive detector systems operating in coincidence-anticoincidence modes. Thanks to an excellent energy resolution and a high efficiency, large volume HPGe detectors have been widely used in low-level gamma-ray spectrometry. In the present paper we discuss the characteristics of single and coincidence (HPGe-NaI(Tl)) arrangements suitable for analysis of environmental samples containing cascade gamma-ray emitters (e.g., 60Co), positron emitters (e.g., 22Na) and single gamma-ray emitters (e.g., 137Cs). The detectors were placed in a large volume shields consisting of iron, lead and copper layers. The reduction of background for the single gamma-ray spectrometer is between 60 and 250, depending on the gamma-ray energy. As an improvement of the apparatus, low detection limits for analysis of 137Cs (0.3 Bq·kg−1) and 60Co (0.1 Bq·kg−1) in environmental samples, respectively, have been obtained.

Restricted access

Summary  

The environmental monitoring system in the counting room of Gamma-Ray Spectrometry Group at the Joǽef Stefan Institute was designed in such a way that it fulfills the requirements of the ISO 17025 standard without causing any additional burden to the staff. In addition to the environmental parameters (temperature, humidity and oxygen concentration in air) the voltage and frequency of the electric power supply and the pressure of the compressed air are monitored. The monitoring system is connected to the main computer and the software automatically checks the recorded data on a daily basis and issues automatic warnings if the recorded values are outside the prescribed limits of acceptance. In this paper, monitoring and control of the environmental and other parameters of the facilities in our laboratory that can affect the measurement result are presented, as well as their time dependencies, correlations among them and correlations between the temperature and the background peak count rates of the spectrometers.

Restricted access

Abstract  

Low-level gamma-ray spectrometry with large volume HPGe detectors has been widely used in analysis of environmental radionuclides. The reasons are excellent energy resolution and high efficiency that permits selective and non-destructive analyses of several radionuclides in composite samples. Although the most effective way of increasing the sensitivity of a gamma-ray spectrometer is to increase counting efficiency and the amount of the sample, very often the only possible way is to decrease the detector’s background. The typical background components of a low-level HPGe detector, not situated deep underground, are cosmic radiation (cosmic muons, neutrons and activation products), radioactivity of construction materials, radon and its progenies. A review of Monte Carlo simulations of background components of HPGe detectors, and their characteristics in coincidence and anti-Compton mode of operation are presented and discussed.

Restricted access