Activity determination of 41Ar using efficiency extrapolation method and 4πβ(PS)-4πγ(NaI) coincidence system

Noble gas 41Ar was measured with a 4πβ-4πγ coincidence system, in which gamma- and beta-rays were respectively detected with a well-type NaI(Tl) and plastic scintillator (PS) detector. The activity of 41Ar was determined from an efficiency extrapolation method, in which the beta detector efficiency was varied by electronic discrimination using the software developed under Visual basic. In addition, high resolution gamma spectroscopy with HPGe detector was also used for activity determination of 41Ar, and the result was satisfactory in agreement with that obtain by the efficiency extrapolation method. This work demonstrated that the activity of 41Ar can be accurately measured by efficiency extrapolation method.