Standardization of ^166mHo in a coincidence system by software and determination of its gamma emission probabilities

This works presents a new standardization of the radionuclide ^166mHo that was carried out at Nuclear Metrology Laboratory (LMN) at IPEN. ^166mHo decays with 1133 years of half-life by beta emission followed by a cascade of gamma-rays in a range of 73 to 1427 keV, and these characteristics makes it a good secondary standard to the calibration of gamma spectrometers. Previously calibrated with a standard 4ℼ(PC)β-γ coincidence system, the same samples were now measured in the Software Coincidence System (SCS), where the data analyses can be done after the measurements, using a software developed at LMN as well. The SCS is composed of a 4ℼ geometry proportional counter operated at 0.1MPa coupled to one NaI(Tl) crystal, positioned above the PC counter, and to a HPGe detector, positioned below the PC counter. The signals from all detectors are digitalized and their pulses height and time of occurrence are recorded on computer files. After the standardization, the emission probabilities per decay of the most intense gamma-rays in the ^166mHo decay were determined by means of a HPGe spectrometer system, which was calibrated with standard sources previously calibrated in the 4ℼ(PC)β-γ coincidence system, and the results were compared with the literature. All the uncertainties were treated by the covariance analysis method. (author)