Development and characterization of novel X-ray detectors for the next generation astronomical observatories

In this talk, I will present recent development and characterization of novel X-ray detectors for X-ray spectroscopy and polarimetry studies. The next generation of large X-ray astronomical missions (e.g. the Lynx Great Observatory and AXIS probe class mission concepts) are planned to have an order-of-magnitude larger collecting areas combined with exquisite mirror quality, enabling unprecedented exploration of the faint and high redshift X-ray universe. An essential component of these mission concepts is the development of focal plane instrumentation with fast readout and excellent noise performance - crucial especially for the soft X-ray performance - on the order of single electrons. MIT Lincoln Laboratory (MIT-LL), MIT Kavli Institute (MKI) and Stanford University (SU) have together made substantial improvements in developing next generation X-ray CCDs, and associated readout electronics to support these detectors. In parallel, we are also working on a novel Single electron Sensitive readout stage (SiSeRO) for CCDs, and potentially active pixel sensors, which can in principle provide even greater responsivity and better noise performance than contemporary CCD technology. Importantly, in these devices, we have also been able to implement Repetitive Non-Destructive Readout (RNDR) technique, achieving significantly improved noise performance. In the next half of the talk, I will focus on the hard X-ray detector development programs in India, primarily optimized for polarimetry studies, e.g. SiPMs, fast scintillators, pixelated CZTs. In this context, the recent spectro-polarimetry results obtained from CZT Imager (CZTI) onboard AstroSat will be discussed. CZTI provides sensitive polarization measurements above 100 keV for bright X-ray sources, e.g. Crab pulsar and the Cygnus X-1 black hole system. Another important characteristic of CZTI is the increasing transparency of the support structure in hard X-rays, which enables it to function as a wide field hard X-ray monitor providing an unique opportunity for GRB detection and polarization measurement. I will conclude with the potential of utilizing fast active pixel sensors (SiSeROs, HCDs), sensitive in soft X-rays and CZTs and the fast SiPM-scintillator systems, sensitive in hard X-rays to develop a unique "all-in-one" instrument to provide simultaneous spectroscopy, timing, polarimetry and imaging in 0.5 - 80 keV.