The Large Area Detector (LAD) is the high-throughput, spectral-timing instrument onboard the eXTP mission, a flagship mission of the Chinese Academy of Sciences and the China National Space Administration, with a large European participation coordinated by Italy and Spain. The eXTP mission is currently performing its phase B study, with a target launch at the end-2027. The eXTP scientific payload includes four instruments (SFA, PFA, LAD and WFM) offering unprecedented simultaneous wide-band X-ray timing and polarimetry sensitivity. The LAD instrument is based on the design originally proposed for the LOFT mission. It envisages a deployed 3.2 m2 effective area in the 2-30 keV energy range, achieved through the technology of the large-area Silicon Drift Detectors - offering a spectral resolution of up to 200 eV FWHM at 6 keV - and of capillary plate collimators - limiting the field of view to about 1 degree. In this paper we will provide an overview of the LAD instrument design, its current status of development and anticipated performance.
The eXTP (enhanced x-ray timing and polarimetry) mission is a major project of the Chinese Academy of Sciences (CAS) and China National Space Administration (CNSA) currently performing a phase B study and proposed for a launch in 2027/2028.
The eXTP scientific payload envisages a suite of instruments offering unprecedented simultaneous wide-band x-ray timing and polarimetry sensitivity. A large European consortium is contributing to the eXTP study and it is expected to provide key hardware elements, including the large area detector (LAD) composed by 40 modules for a total effective area of 3.0 m2 at 6.0 keV.
In this paper we describe the design solutions adopted for the most important thermo-mechanical design drivers of the LAD module, which have been elaborated and used for the demonstration of compliance to the system requirements at spacecraft level. We report in particular the mechanical design for the module and its components, the results of static and dynamic finite element analysis of a simplified model and the preliminary thermal analysis for both a single detailed model and for a reduced model for all the 40 modules of the large area detector. We note that, in parallel to this activity, the LAD module design is being revised and optimized by the LAD consortium. Such design optimization is still ongoing and it is not reported in this paper.
The CubeSat solar polarimeter (CUSP) project aims to develop a constellation of two CubeSats orbiting the Earth to measure the linear polarisation of solar flares in the hard x-ray band by means of a Compton scattering polarimeter on board of each satellite. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures. CUSP is a project approved for a Phase A study by the Italian Space Agency in the framework of the Alcor program aimed to develop CubeSat technologies and missions.
The Pixelated silicon Drift Detector (PixDD) is a two-dimensional multi-pixel X-ray sensor based on the technology of Silicon Drift Detectors, designed to solve the dead time and pile-up issues of photon-integrating imaging detectors. Read out by a two-dimensional self-triggering Application-Specific Integrated Circuit named RIGEL, to which the sensor is bump-bonded, it operates in the 0:5 — 15 keV energy range and is designed to achieve single-photon sensitivity and good spectroscopic capabilities even at room temperature or with mild cooling (< 150 eV resolution at 6 keV at 0 °C). The paper reports on the design and performance tests of the 128-pixel prototype of the fully integrated system.
This paper assesses the response to radiation effects of the RIGEL, the Application Specific Integrated Circuit developed within the framework of the PixDD project, to be coupled with a multi-pixel sensor based on Silicon Drift Detectors for operation at the focal plane of X-ray optics on board space-borne astronomy missions. The campaign was conducted at the heavy ion beam line of the Radiation Effects Facility of the University of Jyvӓskylӓ (Finland): both the response to Single Event Effects (latch-ups and bit flips) and to Total Ionising Dose was evaluated. Experimental data were combined with simulations of the in-orbit environment for two scenarios: an equatorial and a Sun-synchronous orbit. The study demonstrated that the device can be safely operated on an equatorial orbit without any dedicated circuitry to mitigate Single Event Effects, although this precaution is instead advisable in the case of a Sun-synchronous orbit. Spectroscopic degradation resulting from Total Ionising Dose stays below 10% up to 34 krad, a manageable value for both orbital configurations.
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