HALF-LIFE MEASUREMENTS OF EXCITED LEVELS IN THE NANOSECOND AND MICROSECOND REGION
The application of the delayed coincidence technique to accurate half-life measurements of excited levels in the ns and microseconds region will be described. In order to achieve an overall uncertainty of >= 1% on the final value of the half lives a series of precautionary measures depending on the time region have to be considered. In the ns time range the most serious sources of errors are jitter, walk and drift phenomena. To minimize those the time pick-off has to be defined carefully by means of modern fast timing detectors and electronics devices. In the microseconds time range the ratio of true delayed coincidences to chance coincidences influences considerably the final achievable accuracy of the half-life measurements. It must be the aim to reduce the chance coincidence rate as much as possible. In both cases described the procedure used for the analysis of the experimental data is of critical importance. The choice of the analysis region will be discussed. Time calibration and a careful consideration of system linearity, short and long term stability of the entire experimental set-up, are of great importance. Regular checks on these quantities performed during the measurements cycles allow proper quotation of the different systematic uncertainties. As the successful application of the experimental procedures mentioned above the following half-life measurements have been performed: the 37.1 keV level in 121- Sb (3.46 +- 0.03)ns; the 81 keV level in 133-Cs (6.23 +- 0.03)ns; the 482.18 keV level in 181-Ta (10.67 +- 0.05)ns; the 23.87 keV level in 119-Sn (18.03 +- 0.07)ns, the 6.21 keV level in 181-Ta (6.05 +- 0.12)microseconds and the 615.25 keV level in 181-Ta (17.64 +- 0.14)microseconds.
Bibliographic Reference: ICRM SEMINAR ON APPLIED RADIONUCLIDE METROLOGY, GEEL (BELGIUM), MAY 16-17, 1983. AVAILABILITY: CEC LUXEMBOURG, DG XIII/A2 MENTIONING PAPER E 31063 ORA
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Record Number: 1989122007500 / Last updated on: 1987-01-01
Available languages: en