  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 x
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.
