The high definition x-ray imager (HDXI) instrument on the Lynx X-ray Surveyor

Abstract

The Lynx X-ray Surveyor Mission is one of 4 large missions being studied by NASA Science and Technology Definition Teams as mission concepts to be evaluated by the upcoming 2020 Decadal Survey. By utilizing optics that couple fine angular resolution (<0.5 arcsec HPD) with large effective area (~2 m 2 at 1 keV), Lynx would enable exploration within a unique scientific parameter space. One of the primary soft X-ray imaging instruments being baselined for this mission concept is the High Definition X-ray Imager, HDXI. This instrument would achieve fine angular resolution imaging over a wide field of view (~ 22 × 22 arcmin, or larger) by using a finely-pixelated silicon sensor array. Silicon sensors enable large-format/small-pixel devices, radiation tolerant designs, and high quantum efficiency across the entire soft X-ray bandpass. To fully exploit the large collecting area of Lynx (~30x Chandra), without X-ray event pile-up, the HDXI will be capable of much faster frame rates than current X-ray imagers. The planned requirements, capabilities, and development status of the HDXI will be described.

The Lynx X-ray Observatory: concept study overview and status

“…The Lynx architecture is motivated by a dynamic science case to observe the first supermassive black holes and to understand the critical drivers of galaxy and stellar formation and evolution; phenomena only evident at high-energies. Lynx couples a large area, high-resolution, mirror assembly with good wide-field performance (0.5 arcsecond Half Power Diameter (HPD) on-axis, <~1 arcsecond to ~10 arcminutes) to a suite of three science instruments that includes the High Definition X-ray Imager (HDXI) 2,3,4 , the Lynx X-ray Microcalorimeter (LXM) 5 , and the X-ray Grating Spectrometer (XGS) 6,7 . Multiple candidate technologies for the Lynx mirrors exist, three of which are being studied in detail by the Lynx Team.…”

“…In addition, this detector must have excellent soft X-ray spectral response to these (redshifted) sources and have moderate spectral resolution across the ~0.2 to ~10 keV band to deduce thermodynamic properties of the hot gas in galactic halos and other extended objects. A silicon active pixel sensor array of fine pixel scale (0.3 arcsecond) and large format (23 arcminutes x 23 arcminutes FOV), such as HDXI, is capable of meeting these requirements 2 .…”

AXIS: A Probe Class Next Generation High Angular Resolution X-ray Imaging Satellite

“…Charge cloud diffusion in a suitably thick device (∼100 µm depletion) allows centroiding of the incoming photon on sub-pixels scales and somewhat larger pixels of ∼16 µm (0.34 ) can be used. 2,3 Higher readout rates and smaller pixels will substantially reduce the particle background through superior multi-pixel filtering of the larger charge clouds produced by cosmic rays and significantly reduce pile-up from bright point sources. Current CCD technology achieves 2.5 Mpix s −1 transfer rates with readout noise less than 7e-giving good spectral resolution and low energy capability.…”

“…CCD and CMOS detectors with the needed properties are being developed today. 2,3 AXIS has been studied at the NASA Goddard Space Flight Center (GSFC) Instrument and Mission Design Labs (IDL/MDL) and a spacecraft design has been developed using proven spacecraft components and methods for attitude reconstruction compatible with the angular resolution. The estimated mission cost was well below the $1B cost cap for a Probe mission in 2018 dollars.…”

Overview of the high-definition x-ray imager instrument on the Lynx x-ray surveyor

“…The majority of the description in this paper was presented at the SPIE Astronomical Telescopes meeting in 2018 and was reported in the associated proceedings. 5…”