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[en] The experimental setup and procedure for the characterization of the thermal neutron reference field established at the Geesthacht neutron facility (GeNF) of the GKSS is described. The neutron beam, free in air, with a maximum flux of 106 s-1, can easily be reduced to less than 104 s-1 by using a diaphragm variable in size and without changing the beam divergence. Also, the spectral distribution with a mean energy of 45 meV, measured by time-of-flight over a 6.6 m long flight path, is independent of the beam current chosen. In the 2002/2003 experiments reported here, a 6Li glass detector was employed to determine the absolute beam current and to calibrate the 3He transmission beam monitor. In addition, activation measurements of gold foils were carried out at a reduced beam divergence. The results agree within ±2%. Furthermore, the beam is characterized by a low gamma background intensity and a negligible fraction of epithermal neutrons. Irradiations in combination with a scanner device to achieve a homogeneously illuminated scan field have shown that the thermal beam is well suited for dosemeter development and for the calibration of radiation protection instruments. (orig.)
Source
[en] Absolute methods of activity determination and secondary measuring procedures, which are carried out using ionisation chambers for radioactive solutions and NaI(Tl) detectors as well as extended surface proportional counters for solid substances, are the metrological techniques generally available for measurements of radioactivity. The range of methods discussed here was limited to those that are used most frequently in the routine of activity determinations or directly relevant to nuclear medicine or radiation protection. (orig./DG)
[de]
Absolute Verfahren der Aktivitaetsbestimmung und Sekundaermessverfahren mit Ionisationskammern an radioaktiven Loesungen sowie mit NaI(Tl)-Detektoren und Grossflaechen-Proportionalzaehlrohren an Festpraeparaten sind die metrologischen Verfahren fuer Aktivitaetsbestimmungen. Es wurden nur solche Messverfahren behandelt, mit denen in der Praxis Aktivitaetsbestimmungen am haeufigsten durchgefuehrt werden oder die eine direkte Verbindung zur Nuklearmedizin oder zum Strahlenschutz haben. (orig./DG)Source
Rodloff, G.; Debertin, K. (eds.); Physikalisch-Technische Bundesanstalt, Braunschweig (Germany). Radioaktivitaet; 239 p; ISBN 3-89429-178-8; 
; Apr 1992; p. 4-15; 94. PTB seminar: Quality assurance of measurements of activity in nuclear medicine and radiation protection; 94. PTB Seminar: Qualitaetssicherung von Aktivitaetsmessungen in Nuklearmedizin und Strahlenschutz; Braunschweig (Germany); 25-26 Nov 1991
; Apr 1992; p. 4-15; 94. PTB seminar: Quality assurance of measurements of activity in nuclear medicine and radiation protection; 94. PTB Seminar: Qualitaetssicherung von Aktivitaetsmessungen in Nuklearmedizin und Strahlenschutz; Braunschweig (Germany); 25-26 Nov 1991
[en] A complete set of data for the decay scheme of a radionuclide requires knowledge of the emission probabilities of X-rays and Auger electrons. If adopted sets of transition probabilities for the transitions of the decay scheme and atomic shell data (such as fluorescence yields and relative emission probabilities) are available, the emission probabilities of the X-rays and Auger electrons can be calculated from these data. Only data calculated in this way are consistent with the adopted input data and can be compared with measured data. Conclusions can be drawn with respect to the internal consistency of the data sets by comparing the measured and calculated data. Hence, the EMISSION program has been developed and tested to calculate X-ray and Auger electron emission probabilities along with their error propagation
Journal
[en] Low order spline functions are used in a least squares fitting procedure to establish full-energy peak efficiency curves for different kinds of semiconductor photon detectors (Ge(Li), Si(Li), HPGe) in the energy range from 2 keV to 3 MeV. The algorithm allows discontinuities in the efficiency curves due to absorption edges of the detector material to be represented. Uncertainties of the calculated efficiencies are evaluated from the covariance matrix of the experimental data, taking into account correlated data uncertainties. (orig.)
Journal
Nuclear Instruments and Methods in Physics Research, Section A; ISSN 0168-9002; ; CODEN NIMAE; v. 286(3); p. 398-402
; CODEN NIMAE; v. 286(3); p. 398-402
[en] A method is described for determining the depth distribution of the radioactive substance of alpha-emitting nuclides in a wide-area reference source. The method combines measurements and calculations. In the experimental part, the energy spectrum of the source is measured by means of an alpha spectrometer. The energy spectrum is then modelled by the Monte Carlo method, taking into account energy loss of alpha particles in the source matrix, energy-loss straggling and the parameters of the spectrometer. Additional parameters for the characterization of reference sources are derived from the integral of the depth distribution. The investigations prove that the production process of commercial sources can be controlled in such a way that more than 90% of the radioactive material is implanted in the top layer of 5 μm thickness of an aluminum foil
Journal
[en] A VMEbus-based data-acquisition system has been developed for the determinatiuon of the activity of radioactive samples by the correlation-counting method. This technique is particularly well suited for activity measurements in cases where radionuclides decay by cascade processes with relatively long-lived intermediate states and when the classical coincidence method is not applicable, for example. The components of the data-acquisition system and the underlying principles of the correlation-counting method are described. As an example, the absolute standardization of a 75Se solution by means of a pressurized proportional-counter-NaI(Tl)-detector setup is discussed. The correlation-counting method was used to experimentally determine the fraction of genetically correlated event pairs in the proportional counter. (orig.)
Journal
Nuclear Instruments and Methods in Physics Research, Section A; ISSN 0168-9002; ; CODEN NIMAE; v. 299(1-3); p. 292-297
; CODEN NIMAE; v. 299(1-3); p. 292-297
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