Investigation of the minimum detectable activity of radioxenon isotopes using an active guard
One of the current challenges of the Comprehensive Nuclear-Test-Ban Treaty Organization, is reducing the minimum detectable activity and increasing the precision of the detection of radioactive noble gases; namely 135Xe, 133Xe, 133mXe, and 131mXe. These gases are typically detected by systems that use beta-gamma coincidence spectroscopy and gamma spectroscopy for activity measurement. In all of them, a lead shield (passive guard) is used to reduce the environmental isotopes. In this work, the concept of the active guard used in LSC systems has been improved upon for gaseous radioactive samples in a phoswich detector through Geant4 simulations. The simulation results showed that the use of an active guard results in a reduction in the minimum detectable activity, compared to those without an active guard.