  A double-layer silicon detector consisting of two 500micron-thick silicon PIN
photodiodes with independent readouts was mounted in a vacuum chamber and
tested with X-ray sources. The detector is sensitive from 1-30 keV with an
effective area of 6 mm^2. The detector performs best at -35 C with an energy
resolution of 220 eV (FWHM, full width at half maximum) at 5.9 keV, and is able
to operate at room temperature, +25 C, with moderate resolution around 760 eV
(FWHM). The response of the top layer sensor is highly uniform across the
sensitive area. This large-format silicon detector is appropriate for future
X-ray timing missions.
