The Hard X-ray Imager (HXI) is one of three focal plane detectors on board the NeXT (New exploration X-ray
Telescope) mission, which is scheduled to be launched in 2013. By use of the hybrid structure composed of
double-sided silicon strip detectors and a cadmium telluride strip detector, it fully covers the energy range of
photons collected with the hard X-ray telescope up to 80 keV with a high quantum efficiency. High spatial
resolutions of 400 micron pitch and energy resolutions of 1-2 keV (FWMH) are at the same time achieved with
low noise front-end ASICs. In addition, thick BGO active shields compactly surrounding the main detection
part, as a heritage of the successful performance of the Hard X-ray Detector (HXD) on board Suzaku satellite,
enable to achive an extremely high background reduction for the cosmic-ray particle background and in-orbit
activation. The current status of hardware development including the design requirement, expected performance,
and technical readinesses of key technologies are summarized.
A semiconductor Compton camera for a balloon borne experiment aiming at observation in high energy astrophysics
is developed. The camera is based on the concept of the Si/CdTe semiconductor Compton Camera,
which features high-energy and high-angular resolution in the energy range from several tens of keV to a few
MeV. It consists of tightly packed double-sided silicon strip detectors (DSSDs) stacked in four layers, and a
total of 32 CdTe pixel detectors surrounding them. The Compton reconstruction was successfully performed and
gamma-ray images were obtained from 511 keV down to 59.5 keV. The Angular Resolution Measure (ARM) at
511 keV is ~ 2.5 degrees, thanks to the high energy resolution in both the DSSD and CdTe parts.
Double-sided silicon strip detector (DSSD) is a key component to construct the next generation Compton telescope
for the high-sensitivity observation in the energy region from several hundred keV to MeV. The concept of
Compton camera we consider is using DSSD for scatterer, and high-stopping CdTe pixel detector for absorber.
As the scatterer, DSSD has advantages of smaller band gap, higher efficiency of scattering, smaller Doppler
broadening, good response time, and smaller number of readout channels. We have developed and confirmed
that 0.3 mm-thick DSSD has enough performance. As a next step, in order to obtain more efficiency of higher
energy gamma-rays, we developed newly designed DSSD which increase in thickness to 0.5 mm. We measured
the basic properties of 0.5 mm thick DSSD, in terms of leakage current, capacitances, and noise characteristics.
They can be full-depleted around 200 V, and we obtained the energy resolution of 1.3 keV (FWHM) for 60 keV
at -10 °C from one p-side strip. We also set up the newly developed read-out system which is based on technology
of operating ASICs on floating ground, and performed 64 ch read-out on one side.
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