One of the four instruments on the Chinese-European enhanced x-ray timing polarimetry (eXTP) mission is the wide field monitor (WFM), consisting of six coded aperture cameras. The detector plane of each camera is comprised of four 7x7 cm2 silicon drift detectors assembled with similarly sized hybrid circuit board that contain the front-end electronics (FEE) to read out the detectors. The whole assembly needs to be positioned and kept stable within ~50 micron to guarantee the scientific performance of the WFM. The FEE will have analogue ASICs to perform the read-out process. These bare dies are connected to the detector anode output pads. The detector cathodes need to be provided with voltages down to−1300V. Electrical connections between detector, ASICs and FEE are made by bond wires. The hybrid circuit board is a thick film circuit based on 96% Al2O3 which has a coefficient of thermal expansion that is sufficiently close to that of the silicon detector to avoid misalignment due to the large variations in temperature (−50/+60 °C) during assembly and flight. All materials, components and manufacturing processes will have to be without technology originating from the USA. For eXTP’s phase B, we are developing a demonstration model. For this, an early generation ASIC (‘IDeF-X HDBD’) is employed as well as some components that are US-made but for which there is path to European alternatives. The FEE manufacture and the assembly is already completely non-US. We outline the detector/electronics assembly and discuss the main challenges involved.
The eXTP (enhanced x-ray timing and polarimetry) mission is a major project of the Chinese Academy of Sciences (CAS), with a large involvement of Europe. The scientific payload of eXTP includes four instruments: the SFA (spectroscopy focusing array) and the PFA (polarimetry focusing array)—led by China —the LAD (large area detector) and the WFM (wide field monitor)—led by Europe (Italy and Spain). They offer a unique simultaneous wide-band x-ray timing and polarimetry sensitivity. The WFM is a wide field x-ray monitor instrument in the 2-50 keV energy range, consisting of an array of six coded mask cameras with a field of view of 180°x90° at an angular resolution of 5 arcmin and four silicon drift detectors in each camera. Its unprecedented combination of large field of view and imaging down to 2 keV will allow eXTP to make important discoveries of the variable and transient x-ray sky and is essential in detecting transient black holes, that are part of the primary science goals of eXTP, so that they can be promptly followed up with other instruments on eXTP and elsewhere.
The WFM (Wide Field Monitor) instrument of eXTP (Enhanced X-ray Timing and Polarimetry Mission) covers a large fraction of the sky in the (2 - 50) keV energy range, with good angular (5 arcmin - FWHM) and energy (better than 500 eV - FWHM at 6 keV) resolutions. The WFM instrument is part of the scientific payload of the eXTP X-ray satellite, together with the Spectroscopic Focusing Array (SFA), the Large Area Detector (LAD) and the Polarimetry Focusing Array (PFA) instruments. The WFM is distributed in three camera pairs with a broad field of view (180° × 90° FWZR). Each camera is composed by a coded mask assembly, a collimator, a DSP (detector support plate) which hosts four DAs (Detector Assemblies) - each DA including an SDD (Silicon Drift Detector) and its corresponding FEE (Front-End Electronics) - and one BEE (Back-End Electronics). The coded mask area is 260 × 260 mm. It is manufactured from 150 μm thick Tungsten foil. The mask shall keep a flatness of ±50 μm over its surface for the whole operating temperature range of the WFM instrument. A pretension mechanism is carried out with a set of mask frames to fulfil this requirement. A collimator structure supports the coded mask assembly and the detector box. The collimator will provide the stiffness required to avoid deformations due to accelerations and thermal stresses. In this paper, we present the mechanical design drivers of the camera structure (i.e. coded mask assembly, collimator and DSP), the alignment procedure of the detector plane (i.e. the four Silicon tiles) and the detector plane with the coded mask and the camera thermal control system.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.