High Efficiency Semiconductor Arrays for Hard X-Ray Imaging

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 ⁰C, compared to ~ 1100 ⁰C 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.