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Development and characterization of fast low noise X-ray detectors for the next generation astronomical observatories

Presentation #103.14 in the session Missions and Instruments.

Published onJul 01, 2023
Development and characterization of fast low noise X-ray detectors for the next generation astronomical observatories

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. We recently characterized a prototype CCD at 4 Megapixel/s (40 times faster than Chandra CCDs) with good noise performance. 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 JFET technology. The SiSeRO technology uses a p-MOSFET transistor with a depleted back gate region beneath the transistor channel. The transistor source-drain current is modulated by the transfer of charge into the back gate region. The first SiSeRO prototype devices already achieve a charge to current conversion gain of >700 pA per electron, an equivalent noise charge (ENC) of 4.5 electrons root mean square (RMS), and a full width half maximum (FWHM) of 130 eV at 5.9 keV at a readout speed of 625 Kpixel/s. Importantly, utilizing the benefit that the charge signal remains unaffected by the readout process in these devices, we have also been able to implement Repetitive Non-Destructive Readout (RNDR) on our prototype devices, achieving significantly improved ENC performance. In this presentation, we discuss the characterization test results for these new fast, low noise X-ray CCDs and novel SiSeRO devices, along with a multi-channel readout ASIC system developed at SU to enable rapid, low noise, low power parallel readout of these devices.

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