The next generation of wide-field survey instruments with improved angular and energy resolution for research into astrophysical transient X-ray phenomena is currently under development. A scalable detector plane architecture has been developed at Harvard using CZT detector arrays for use in high resolution coded-aperture telescopes.
Despite decades of research, the yield of device grade CZT is still quite low. In addition, internal defects cause spatial distortions in images. To meet the needs of hard X-ray astronomy a lower cost, more uniform and more readily available alternative to CZT is desirable.
Thallium bromide (TlBr) has higher density and atomic number than CZT and therefore higher stopping power at hard X-ray energies. TlBr has a low melting point (460 °C, compared to ~ 1100 °C for CZT) and cubic crystal structure and can be grown from the melt by low cost techniques. As a result, TlBr has the potential to be a more efficient, lower cost alternative to CZT in the detector plane architecture developed by Harvard for use in high resolution coded-aperture telescopes.
TlBr imaging arrays should be suitable for wide-field hard X-ray coded-aperture imagers currently under development (cf. ProtoEXIST and HREXI). This technology should eventually be employed as part of a Medium Class Explorer (MIDEX) mission to probe X-ray transient phenomena with improved sensitivity, energy resolution and angular resolution. This will enable monitoring of phenomena, including tidal disruption events (TDE), supernova (SN), soft-gamma repeaters (SGR), X-Ray Flashes (XRF), as well as neutron stars (NS) and black holes (BHs).
Non-NASA applications include nuclear and particle physics, nuclear non-proliferation, medical imaging, environmental monitoring, non-destructive testing, and geological exploration. Nuclear medicine techniques such as single photon emission computed tomography (SPECT) would also benefit from the development of this detector technology.