Studying the use of Thallium Bromide as a Gamma Ray Sensor
Olivia Voyce (1), Tim Veal (1), Dan Judson (1), Paul Nolan (1), Amlan Datta (2), Laura Harkness-Brennan (1)
(1) The University of Liverpool Physics Department, (2) CapeSym Inc.
Gamma ray spectroscopy is a common assay method used in the identification and characterisation of radioactive samples at nuclear sites as it can be used to extensively survey, identify and assess the magnitude of waste in contaminated areas of such facilities. Following on from the results of a NuSeC summer project research is being undertaken at the University of Liverpool , with collaboration from CapeSym inc. into the development of a ground breaking, novel detector fabricated from the compound semiconductor Thallium Bromide (TlBr). This material is expected to excel as a portable, room temperature detector owing to its wide band gap (2.68eV), large bulk resistivity (10^10-10^11Ωcm) and high detection efficiency. Composition from high atomic number elements (ZTl=81, ZBr=35) and large density of 7.56 g/cm3 equips TlBr sensors with enhanced sensitivity compared to existing competing materials such as CZT. The long term performance of these sensors however is inhibited by the degradation of the device through ionic polarization of the crystal and subsequent reaction of bromine with the electrode materials. To this end, studies are currently underway to assess and quantify the mechanism of this phenomenon, in addition to developing methods to inhibit the degradation. The expected outcome of this work is the development of a novel portable gamma ray sensor with significantly reduced counting times and improved isotope identification compared to existing technologies, this will be discussed in the presentation. Furthermore, the fabrication methods of TlBr detectors as well as current energy resolution results will be presented, in addition to a discussion of the limitations of manufacturing these detectors.