  We present preliminary characterization of the Speedster-EXD, a new event
driven hybrid CMOS detector (HCD) developed in collaboration with Penn State
University and Teledyne Imaging Systems. HCDs have advantages over CCDs
including lower susceptibility to radiation damage, lower power consumption,
and faster read-out time to avoid pile-up. They are deeply depleted and able to
detect x-rays down to approximately 0.1 keV. The Speedster-EXD has additional
in-pixel features compared to previously published HCDs including: (1) an
in-pixel comparator that enables read out of only the pixels with signal from
an x-ray event, (2) four different gain modes to optimize either full well
capacity or energy resolution, (3) in-pixel CDS subtraction to reduce read
noise, and (4) a low-noise, high-gain CTIA amplifier to eliminate interpixel
capacitance crosstalk. When using the comparator feature, the user can set a
comparator threshold and only pixels above the threshold will be read out. This
feature can be run in two modes including single pixel readout in which only
pixels above the threshold are read out and 3x3 readout where a 3x3 region
centered on the central pixel of the x-ray event is read out. The comparator
feature of the Speedster-EXD increases the detector array effective frame rate
by orders of magnitude. The new features of the Speedster-EXD hybrid CMOS x-ray
detector are particularly relevant to future high throughput x-ray missions
requiring large-format silicon imagers.
