Micro hard-X ray camera: From Caliste 64 to Caliste 256

Caliste project aims at hybridizing 1 cm² Cd(Zn)Te detectors with low noise front-end electronics, in a single component standing in a 1 × 1 × 2 cm³ volume. The micro-camera is a spectro-imager for X and gamma rays detection, with time-tagging capability. Hybridization consists in stacking full custom ASICs perpendicular to the detection surface. The first prototype Caliste 64 integrates a detector of 8 × 8 pixels of 1 mm pitch. Fabrication and characterizations of nine cameras samples validate the design and the hybridization concept. Spectroscopic tests result in a mean energy resolution of ∼0.7 keV FWHM at 14 keV and ∼0.85 keV FWHM at 60 keV with 1 mm-thick Al Schottky CdTe detectors biased at −400V and cooled down to −15°C. The new prototype called Caliste 256 integrates 16 × 16 pixels of 580 8m pitch in the same volume as Caliste 64. Electrical tests with the first sample fabricated without detector result in a mean equivalent noise charge of 64 el. rms (9.6 μs, no leakage current). Caliste devices are 4-side buttable and can be used as elementary detection units of a large hard X-ray focal plane, as for the 64 cm² high energy detector of the Simbol-X astronomical space mission.