C. Blondel

In flight calibration of the ISGRI camera

ISGRI, the IBIS low energy camera (15 keV - 1 MeV) on board INTEGRAL, is the first large CdTe gamma-ray imager in orbit. We present here an overview of the ISGRI in-flight calibrations performed during the first months after launch. We discuss the stability of the camera as well as the CdTe pixels response under cosmic radiation. The energy calibrations were done using lead and tungsten fluorescence lines and the

IDeF-X V1.0: performances of a new CMOS multi channel analogue readout ASIC for Cd(Zn)Te detectors

\mathrm{^{22}Na}

A CdTe gamma-camera for the space observatory INTEGRAL: software charge-loss corrections

calibration unit. Thermal effects and charge correction algorithm are discussed, and the resulting energy resolution is presented. The ISGRI background spatial and spectral non-uniformity is also described, and some image correction results are presented.

Caliste HD: A new fine pitch Cd(Zn)Te imaging spectrometer from 2 keV up to 1 MeV

The evolution of the CdTe detector properties (leakage current, capacitance, and geometry) requires a continuous improvement of the electronic frond-end in terms of geometry, noise, and power consumption. This is why our group is working on a new modular spectro-imaging system based on CdTe detectors coupled to dedicated full custom readout ASICs, named IDeF-X for imaging detector front-end. We present the most recent version of IDeF-X which is a sixteen-channel analogue readout chip for hard X-ray spectroscopy. It has been processed with the standard AMS 0.35 /spl mu/m CMOS technology. Each channel consists of a charge sensitive preamplifier, a pole zero cancellation stage, a variable peaking time filter and an output buffer. IDeF-X is designed to be DC coupled to detectors having a low dark current at room temperature and is optimized for input capacitance ranging from 2 to 5 pF.

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

Abstract The IMAGER gamma-ray telescope on board INTEGRAL features a coded aperture and a two-layer detector. The first of these layers, ISGRI, is a 16 384 pixel CdTe gamma-camera which will operate in the 20 keV–1 MeV energy range. The spectral performances of ISGRI at energies greater than 50 keV are obtained using a software charge-loss correction based on pulse rise-time measurements. At high energy, the study of the Compton interactions between the two IMAGER layers should ensure a good background rejection. This device will provide unprecedented performances in this energy range: a spatial resolution of 4 mm, a spectral resolution better than 7% at 122 keV and a broad band sensitivity at 3σ of about 10 −6 cm −2 s −1 keV −1 at 100 keV for a 10 5 s observation. Galactic X-ray binary sources, supernovae and active galactic nuclei will be prime targets for ISGRI.

Low Energy Characterization of Caliste HD, a Fine Pitch CdTe-Based Imaging Spectrometer

Caliste HD is the last member of the Caliste family of Cd(Zn)Te micro-cameras for space applications. This hybrid component is made of the assembly of one 16 × 16 pixel Cd(Zn)Te detector and eight analog front-end ASIC named IDeF-X HD equipped with 32 spectroscopic channels. The pixels are 625 µm pitch and are surrounded by a 20 µm wide guard ring. The new generation of ASIC has the advantage of having a power consumption 4 times lower as the previous version (0.2 W for the full device) and offers the possibility to extend the dynamic range from 250 keV to 1 MeV. The technology is fully compliant with operation in space (tolerant to radiation, thermal and mechanical constraints). This paper presents the preliminary spectroscopic results obtained with the samples produced so far. At −16°C the sum spectrum built with all single events of the 1 mm-thick Al Schottky detector show an energy resolution of 0.82 keV FWHM at 14 keV and 0.92 keV FWHM at 60 keV. A good uniformity in gain and in noise is measured over the 256 pixels; the low level-threshold is lower than 2 keV for all pixels.

Caliste-SO: the x-ray spectrometer unit of the STIX instrument onboard the Solar Orbiter space mission

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.

The High Energy Detector of Simbol‐X

Caliste HD is a recently developed micro-camera designed for X and gamma-ray astronomy, based on a 1×1 cm2 CdTe Schottky pixelated detector. Its entire surface is composed of 256 pixels, disposed on a 16 × 16 pixel array. This spectrometer is buttable on its 4 sides and can be used to create a large focal plane. It is also designed for space environment. Its IDeF-X front-end electronics has low power consumption, excellent noise performance and a wide dynamic range, from 2 keV to 1 MeV. Moreover, electronic noise performances of this device were optimized to set the low level energy threshold lower than 2 keV.

Caliste 64: detection unit of a spectro imager array for a hard x-ray space telescope

Caliste-SO is a hybrid detector integrating in a volume of 12 × 14 × 18 mm3 a 1 mm-thick CdTe pixel detector, a frontend IDeF-X HD ASIC and passive parts to perform high resolution spectroscopy in the 4-200 keV energy range with high count rate capability (104-105 photons/s/cm2). The detector hybridization concept was designed by CEA and 3DPlus to realize CdTe cameras for space astronomy missions with various pixel patterns. For the STIX instrument onboard the Solar Orbiter mission, the imaging system is made by 32 collimators that sample the visibilities of the spatial Fourier transform and doesn’t require fine pitch pixels. The Al-Schottky CdTe detectors produced by Acrorad are then patterned and tested by the Paul Scherrer Institute to produce 12 pixels surrounded by a guard ring within 1 cm2. Electrical and spectroscopic performance tests of the Caliste-SO samples are performed in France at key manufacturing steps, before sending the samples to the principal investigator to mount them in the Detector Electronics Module of STIX in front of each collimator. Four samples were produced in 2013 to be part of the STIX engineering model. Best pixels show an energy resolution of 0.7 keV FWHM at 6 keV (1 keV resolution requirement for STIX) and a low-level detection threshold below 3 keV (4 keV requirement for STIX). The paper describes the design and the production of Caliste-SO and focuses on main performance tests performed so far to characterize the spectrometer unit.

Flight production of Caliste-SO: the hard x-ray spectrometers for solar orbiter/STIX instrument

The High Energy Detector (HED) is one of the three detection units on board the Simbol‐X detector spacecraft. It is placed below the Low Energy Detector so as to collect focused photons in the energy range from 8 to 80 keV. It consists of a mosaic of 64 independent cameras, divided in 8 sectors. Each elementary detection unit, called Caliste, is the hybridization of a 256‐pixel Cadmium Telluride (CdTe) detector with full custom front‐end electronics into a unique component. The status of the HED design will be reported. The promising results obtained from the first micro‐camera prototypes called Caliste 64 and Caliste 256 will be presented to illustrate the expected performance of the instrument.