Nuclear explosion monitoring is performed globally using seismic, infrasound, hydroacoustic, and radioxenon technologies. Of these four technologies, only radioxenon monitoring can uniquely attribute a detected explosion as nuclear. The International Monitoring System (IMS) detects radioxenon in the atmosphere with detectors based on plastic organic and sodium iodide scintillators. These detectors are sensitive to the coincident beta and gamma-ray signatures in the radioxenon decays: the plastic is used to detect the betas and the sodium is used to detect the gamma rays. The poor energy resolution of plastic scintillator limits the sensitivity of these systems to the metastable xenon isotopes. Recently developed organic scintillators such as stilbene and organic glass offer increased light output and improved energy resolution, making them attractive for this application. We will use MCNP to perform Monte Carlo simulations to optimize the geometry of a beta detector made of stilbene and organic glass for detecting coincident beta and gamma-ray events. Once we determine the optimum geometries, we will use Geant4 to characterize the optical transport behavior within the detector. The unique geometry of the beta detectors deployed in radioxenon detection systems makes scintillation light transport and collection a non-trivial problem that affects energy resolution. We will apply both simulation modalities to identify detector geometries with higher coincidence detection efficiency and energy resolution, thereby improving isotopic identification and decreasing the minimum detectable amount of radioxenon in the detector. In the full paper, we present these optimum detector geometries along with a sensitivity analysis for the detection of the various radioxenon isotopes.
Year
2020
Abstract