A new triple-to-double coincidence ratio (TDCR) system has been established at CMI as an additional technique for primary activity standardisation. Details of the detectors and the electronics are given. Construction of the optical chamber was validated using measurement of a (3)H standard-the efficiency achieved with Ultima Gold was 58%. Several methods of efficiency variation (coloured bands painted on vial, positioning and photomultipliers defocussing) are compared. Activity concentrations of (204)Tl and (45)Ca were determined with the TDCR method and with the efficiency tracer technique. Advantages of the TDCR method compared to the efficiency tracing method and agreement between results are shown.
- MeSH
- analýza selhání vybavení MeSH
- dávka záření MeSH
- design vybavení MeSH
- internacionalita MeSH
- poločas MeSH
- radioizotopy thallia analýza normy MeSH
- radioizotopy vápníku analýza normy MeSH
- radiometrie přístrojové vybavení normy MeSH
- referenční hodnoty MeSH
- referenční standardy MeSH
- Publikační typ
- časopisecké články MeSH
The activities of 54Mn and 65Zn have been determined by 4pi(PC)-gamma coincidence counting, with efficiency variation performed by the conventional method of altering the self-absorption in the sources as well as by the computer discrimination method. The standardisation of 65Zn presents some complications requiring optimisation of the gamma-ray energy window settings to achieve a linear efficiency-extrapolation curve. Determination of these optimal settings by the conventional coincidence method is a tedious task. These difficulties have been reduced by the utilisation of a software coincidence counting system that records time and amplitude information of individual pulses from coincidence measurements, where the coincidence parameters are set after the data collection process has completed, facilitating multiple data evaluations on a single data set. The optimal gamma-ray energy window settings for the 65Zn standardisation were derived from the results of the 54Mn standardisation, as well as from studies of the 65Zn data itself. The setting of the PC channel thresholds for K and both (K+L) electrons is also discussed. The results are compared with those attained using conventional coincidence counting.
- MeSH
- algoritmy MeSH
- dávka záření MeSH
- mangan analýza normy MeSH
- radioizotopy zinku analýza normy MeSH
- radionuklidy analýza normy MeSH
- referenční hodnoty MeSH
- referenční standardy MeSH
- reprodukovatelnost výsledků MeSH
- scintilace - počítání metody normy MeSH
- senzitivita a specificita MeSH
- směrnice jako téma MeSH
- software MeSH
- spektrometrie gama metody normy MeSH
- Publikační typ
- hodnotící studie MeSH
- Geografické názvy
- Česká republika MeSH
