The Chinese-French space mission SVOM (Space-based multi-band Variable Object Monitor) due to be launched in 2021 is dedicated to the study of the transient sky, in particular Gamma-Ray Bursts. SVOM will play a key role in the time-domain and multi-messenger astronomy by providing regular alerts to the ground and space facilities, as well as ensuring a broadband follow-up of the sources from X-rays to near infrared. ECLAIRs is the prime instrument onboard the SVOM mission detecting automatically new transient within its field of view and providing their first localization. This telescope is a wide-field coded-mask imager working in the 4-150 keV band. It will sample the temporal and spectral properties of the detected GRBs. The detection plane of this instrument is made of 6400 Schottky CdTe detectors coupled to a low-noise front end electronics. Building a reliable spectral response model of the detection plane is important to retrieve the appropriate spectral parameters of astrophysical sources observed by ECLAIRs. In this paper, we present our MonteCarlo spectral response model of the ECLAIRs detection plane taking into account the main radiation-matter interactions, the physical properties of the detectors. Then, we show how we calibrated this model using lab measurements, leading to the computation of the first realistic spectral response matrix. This work also enabled us to investigate in details the physical properties of a large sample of Schottky CdTe detectors. We discuss in this paper the performances of these detectors.
ECLAIRs is a 2-D coded-mask imaging telescope on-board the Sino-French SVOM space mission, in order to detect and locate precisely Gamma-ray bursts (GRBs) in the 4 - 150 keV energy range. Its design has been drawn by the central objective of achieving a low-energy threshold of 4 keV. In that respect, the camera is formed by 6400 Schottky CdTe detectors organized on elementary hybrid matrices of 4 × 8 pixels, which will be polarized up to -450V and operated at - 20°C. The remarkable low-energy threshold homogeneity required for the detection plane has been achieved thanks to an extensive characterization of the innovative hybrid module composed of 32 CdTe detectors, associated to a very lownoise 32-channel ASIC chip, and both assembled on specific ceramics. In this paper, we outline the SVOM space mission, and then describe the ECLAIRs instrument. We continue by focusing on the different elements of the camera prototype named “ProtoDPIX”. Indeed, this is a very important step for the project because it is the first time we are working in Camera Mode with 800 detectors. Then, we present some spectral results obtained from this, to show its great spectroscopic performance, after explaining the setup. Thus, we performed a large spectral measurements campaign at the regulated temperature of -20°C, using several calibrated radioactive sources (241Am and 57Co). Moreover, we will resume the future steps of development of the final flight model camera and the different constraints due to the short planning and the very challenging technical requirements. In conclusion, thanks to this prototype we are in the process of validating a complete detection chain, from the detectors to the backend electronics, and from mechanical study through thermal design. Finally, we are checking the performance to be ready for integration, functional tests and calibration stages.