Microwave Readout to Enable the Imaging Spectrometer for the X-ray Surveyor

The X-ray Surveyor mission concept is one of NASA’s four large missions to be studied in the upcoming 2020 Astrophysics Decadal Review. It aims to be a true follow-on to the Chandra X-ray Observatory, retaining the exquisite < 1 arcsec angular resolution in the soft x-ray band (0.3–12 keV) but with a much larger collecting area and improved instrumentation, including a non-dispersive imaging spectrometer. This combination will enable observations essential to understanding the earliest galaxies and supermassive black holes, as well as galaxy formation and the assembly of large-scale structure from the earliest epochs.Microcalorimeters are non-dispersive devices that have achieved excellent energy resolution, providing resolving powers of  >3000 at 6 keV. They are the leading detector technology for high-resolution x-ray imaging spectrometers, and the X-ray Surveyor as currently envisaged includes a microcalorimeter instrument. But, the surveyor instrument will require a hundred times the number of pixels compared to our state-of-the-art microcalorimeter arrays: a hundred thousand pixels are needed­ to match the spatial resolution of the X-ray Surveyor optic while covering 5'x 5'.  This project aims to increase the technical readiness of the readout technology that is suitable for these large microcalorimeter arrays. In collaboration with colleagues at NIST, Boulder, we will perform readout demonstrations of transition-edge-sensor microcalorimeters using microwave SQUID multiplexer chips and newly acquired room-temperature readout electronics.