Author/Authors :
Kraft، نويسنده , , S. and Andrianov، نويسنده , , V. and Bleile، نويسنده , , A. and Egelhof، نويسنده , , P. and Golser، نويسنده , , R. and Kiseleva، نويسنده , , A. and Kiselev، نويسنده , , O. and Kutschera، نويسنده , , W. and Meier، نويسنده , , J.P. and Priller، نويسنده , , A. K. Shrivastava، نويسنده , , A. and Steier، نويسنده , , P. and Vockenhuber، نويسنده , , C.، نويسنده ,
Abstract :
For the first time, calorimetric low-temperature detectors were applied in accelerator mass spectrometry, a well-known method for determination of very small isotope ratios with high sensitivity. The aim of the experiment was to determine with high accuracy the isotope ratio of 236U/238U for several samples of natural uranium, 236U being known as a sensitive monitor for neutron flux. Measurements were performed at the VERA tandem accelerator at Vienna, Austria. The detectors consist of sapphire absorbers and superconducting transition edge thermometers operated at T≈ 1.5 K. The relative energy resolution obtained for 17.39 MeV 238U is ΔE/E=4–9×10−3, depending on the experimental conditions. This performance enabled to substantially reduce background from neighbouring isotopes and to increase the detection efficiency. Due to the high sensitivity achieved, a value of 236U/238U=6.5×10−12 could be obtained, representing the smallest 236U/238U ratio measured until now.
