A NEW HIGHLY EFFICIENT SET-UP FOR CYCLIC AND PSEUDOCYCLIC SHORT-TIME ACTIVATION-ANALYSIS WITH HIGH COUNT RATES

A new counting geometry with a simple sample changer was constructed t o enable cyclic and pseudocyclic short-time activation analysis. With the new system it is possible to cycle a sample, or successively an in definite number of samples up to 20 times. The sample changer acts at the same time as sample catcher for two n-type HPGe detectors and can release the sample into a well-type HPGe detector. The new system enab les the simultaneous counting of the irradiated samples by means of tw o endcap HPGe detectors, and subsequent counting by means of the well HPGe detector or both detector types. A well detector ensures a high c ounting efficiency which improves the sensitivity of a large number of short lived nuclides. Some standard reference materials (i.e., BCR-17 6, NIST SRM 1633b, IAEA-336, 335b, 335c) were prepared and analysed in replicates. The results indicate that up to 46 nuclides can be determ ined in BCR-176 if the samples are irradiated with and without the (Li D)-Li-6 converter. An automatic evaluation programme was developed tha t determines the FWHM calibration parameters for each spectrum for acc urate peak-area estimation at high count rates.