The Microchannel X-ray Telescope (MXT) for the Space-based multi-band astronomical Variable Objects Monitor (SVOM), a Franco-Chinese mission (CNES/CNSA), is designed for the soft X-ray range (0.2-10 KeV) to observe gamma-ray bursts (GRBs) from the beginning to the afterglow emission. In the past years, the PANTER test facility has been testing the different MXT optics models. Each optic is made up of an array of 5 x 5 Micro Pore Optic (MPO) plates. We characterized the performance of the SVOM optic at different phases: Bread-Board (BB), Qualification Model (QM), Flight Model (FM), and Flight Spare (FS) for the optic followed by the Performance Model (PM) and Flight Model (FM) for the complete telescope fully integrated with the optic, detector, radiator and electronics. For the FM end-to-end test, in October 2021, the goal was to determine the half-energy width (HEW) on-axis and off-axis, and to characterize the flight telescope's energy-dependent efficiency (effective area) under different thermal loads, i.e. different detector and optics temperatures. The final numbers will be presented in a paper in preparation. This paper provides the overview of various activities: setup, metrology and measurement, carried out at the PANTER facility during the development of the SVOM-MXT towards the end-to-end test.
SVOM (space-based multi-band astronomical variable objects monitor) is a mission developed within a Sino-French cooperation context and dedicated to the detection, localization and study of gamma ray bursts (GRBs) and other high-energy transient phenomena. Four instruments, operating in different wavelengths, are implemented on board in order to perform GRB detection and observations. The MXT instrument, developed by the National French Space Agency (CNES) in collaboration with CEA, MPE, IJCLab and the University of Leicester, is dedicated to the observation of GRB afterglows in the soft x-ray band and is one of the four instruments implemented on the Chinese satellite. First the design chosen of this instrument will be described and then the main results of the qualification campaign performed with the development models as EQM or STM and PFM models will be presented, as much at the instrument level as at the SVOM satellite QM level. Then, we will present how flight model design has been updated regarding the qualification campaign results. Furthermore, it will be presented how the performance of this kind of instrument is evaluated or measured through several models at sub system level or at instrument level. Finally, we will provide as a conclusion the main steps which have been achieved for this kind of development and give our main feedback.
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 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 enhanced x-ray timing and polarimetry (eXTP) mission is a large innovative observatory in the field of x-ray astronomy, designed to study the properties of matter under extreme conditions of density, gravity, and magnetic fields. It is developed by an international consortium led by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS) and is currently completing phase-B with a launch foreseen in 2027. Two of the four instruments onboard eXTP will be provided by a European consortium: the large area detector (LAD) and the wide field monitor (WFM). These two instruments use a high number of large area silicon drift detectors (SDDs) that are organized in 40 modules of 16 detectors each for the LAD and in six coded-aperture cameras with four detectors each for the WFM. The high multiplicity and modularity of this concept as well as the high data rates call for a novel, hierarchical data processing scheme. A similar concept is applied in the data acquisition and processing system of the LAD and the WFM. silicon drift detector and front end electronics using ASIC technology constitute the detector assembly. Data processing is performed in an FPGA-based digital circuit using only ITAR-free components in order to facilitate export to the launch site in China. The design of the digital electronics is not yet finally frozen, but the development and manufacturing of demonstrator models have been already completed. The FPGA firmware based on the pipeline data processing concept has been developed in VHDL. This concept allows real-time data processing capabilities and reduces dead time, thus improving the detection capacity for high flux sources.
Hard x-/soft gamma-ray astronomy (>100 keV) is a crucial field for the study of important astrophysical phenomena such as the 511 keV positron annihilation line in the galactic center region and its origin, gamma-ray bursts, soft gamma-ray repeaters, nuclear lines from SN explosions and more. However, several key questions in this field require sensitivity and angular resolution that are hardly achievable with present technology. A new generation of instruments suitable to focus hard x-/soft gamma-rays is necessary to overcome the technological limitations of current direct-viewing telescopes. One solution is using Laue lenses based on Bragg’s diffraction in a transmission configuration. To date, this technology is in an advanced stage of development and further efforts are being made in order to significantly increase its technology readiness level (TRL). To this end, massive production of suitable crystals is required, as well as an improvement of the capability of their alignment. Such a technological improvement could be exploited in stratospheric balloon experiments and, ultimately, in space missions with a telescope of about 20 m focal length, capable of focusing over a broad energy pass-band. We present the latest technological developments of the TRILL (technological readiness increase for Laue lenses) project, supported by ASI, devoted to the advancement of the technological readiness of Laue lenses. We show the method we developed for preparing suitable bent germanium and silicon crystals and the latest advancements in crystals alignment technology.
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 Microchannel X-Ray Telescope (MXT) is part of the Sino French SVOM mission mainly dedicated to Gamma-Ray Bursts (GRBs). MXT combines a “lobster-eye” focusing X-ray micro-pore optic with a pnCCD detector operating from 0.1 to 10 keV. A stable structure made of carbon fiber reinforced polymer (CFRP) and titanium connects the two parts and provides the interfaces with the satellite. After a short description of the instrument, this paper first presents the alignment process and the measurement of the line of sight (LOS) at MPEs PANTER facility in Germany. Then we focus on the prediction of the in-orbit LOS stability combining thermos-elastic simulations and dedicated measurements.
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 an extended phase A study and proposed for a launch by 2025 in a low-earth orbit. The eXTP scientific payload envisages a suite of instruments (Spectroscopy Focusing Array, Polarimetry Focusing Array, Large Area Detector and Wide Field Monitor) offering unprecedented simultaneous wide-band X-ray spectral, timing and polarimetry sensitivity. A large European consortium is contributing to the eXTP study and it is expected to provide key hardware elements, including a Large Area Detector (LAD). The LAD instrument for eXTP is based on the design originally proposed for the LOFT mission within the ESA context. The eXTP/LAD envisages a deployed 3.4 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 provide an overview of the LAD instrument design, including new elements with respect to the earlier LOFT configuration.
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 an extended phase A study and proposed for a launch by 2025 in a low-earth orbit. The eXTP scientific payload envisages a suite of instruments (Spectroscopy Focusing Array, Polarimetry Focusing Array, Large Area Detector and Wide Field Monitor) 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 a Wide Field Monitor (WFM). The WFM instrument for eXTP is based on the design originally proposed for the LOFT mission within the ESA context. The eXTP/WFM envisages a wide field X-ray monitor system in the 2-50 keV energy range, achieved through the technology of the large-area Silicon Drift Detectors. The WFM will consist of 3 pairs of coded mask cameras with a total combined Field of View (FoV) of 90×180 degrees at zero response and a source localization accuracy of ~1 arcmin. In this paper we provide an overview of the WFM instrument design, including new elements with respect to the earlier LOFT configuration, and anticipated performance.
The SVOM (Space-based multi-band astronomical Variable Objects Monitor) French-Chinese mission is dedicated to the detection, localization and study of Gamma Ray Bursts (GRBs) and other high-energy transient phenomena. We first present the general description of the French payload composed of the ECLAIRs instrument, dedicated to GRB detection and localization and the MXT instrument, dedicated to GRB follow-up observation in soft X-ray band. Then the paper describes more in detail the design and the performances of the MXT instrument, finally a status of MXT development will be given.
O. Limousin, A. Meuris, F. Lugiez, Olivier Gevin, F. Pinsard, C. Blondel, I. Le Mer, E. Delagnes, M.C. Vassal, F. Soufflet, R. Bocage, A. Penquer, M. Billot
In the frame of the hard X-ray Simbol-X observatory, a joint CNES-ASI space mission to be flown in 2014, a prototype of miniature Cd(Zn)Te camera equipped with 64 pixels has been designed. The device, called Caliste 64, is a spectro-imager with high resolution event timetagging capability. Caliste 64 integrates a Cd(Zn)Te semiconductor detector with segmented electrode and its front-end electronics made of 64 independent analog readout channels. This 1 × 1 × 2 cm3 camera, able to detect photons in the range from 2 keV up to 250 keV, is an elementary detection unit juxtaposable on its four sides. Consequently, large detector array can be made assembling a mosaic of Caliste 64 units. Electronics readout module is achieved by stacking four IDeF-X V1.1 ASICs, perpendicular to the detection plane. We achieved good noise performances, with a mean Equivalent Noise Charge of ~65 electrons rms over the 64 channels. For the first prototypes, we chose Pt//CdTe//Al/Ti/Au Schottky detectors because of their very low dark current and excellent spectroscopic performances. Recently a Caliste 64 prototype has been also equipped with a 2 mm thick Au//CdZnTe//Au detector. This paper presents the performances of these four prototypes and demonstrates spectral performances better than 1 keV fwhm at 59.54 keV when the samples are moderately cooled down to -10°C.
The Microchannel X-ray Telescope (MXT) is a soft X-rays instrument on board SVOM, a Sino French mission. The launch is planned in 2021 by a LM-2C rocket. The main SVOM general objective is the survey of Gamma Ray Bursts, in coordination with ground telescopes. The other main on board instruments are ECLAIR (gamma, french), GRM (gamma, Chinese) and VT (visible, chinese).
KEYWORDS: Sensors, Electronics, Analog electronics, CCD image sensors, Charge-coupled devices, Sensors, Electronics, Analog electronics, High energy astrophysics, Capacitors, Silicon, Electronic filtering, Signal detection
In most of embedded imaging systems for space applications, high granularity and increasing size of focal planes justify an almost systematic use of integrated circuits. . To fulfill challenging requirements for excellent spatial and energy resolution, integrated circuits must fit the sensors perfectly and interface the system such a way to optimize simultaneously noise, geometry and architecture. Moreover, very low power consumption and radiation tolerance are mandatory to envision a use onboard a payload in space. Consequently, being part of an optimized detection system for space, the integrated circuit is specifically designed for each application and becomes an Application Specific Integrated Circuits (ASIC). The paper focuses on mixed analog and digital signal ASICs for spectro-imaging systems in the keVMeV energy band.
The first part of the paper summarizes the main advantages conferred by the use of front-end ASICs for highenergy astrophysics instruments in space mission. Space qualification of ASICs requires the chip to be radiation hard. The paper will shortly describe some of the typical hardening techniques and give some guidelines that an ASIC designer should follow to choose the most efficient technology for his project.
The first task of the front-end electronics is to convert the charge coming from the detector into a voltage. For most of the Silicon detectors (CCD, DEPFET, SDD) this is conversion happens in the detector itself. For other sensor materials, charge preamplifiers operate the conversion. The paper shortly describes the different key parameters of charge preamplifiers and the binding parameters for the design. Filtering is generally mandatory in order to increase the signal to noise ratio or to reduce the duration of the signal. After a brief review on the main noise sources, the paper reviews noise-filtering techniques that are commonly used in Integrated circuits designs.
The way sensors and ASICs are interconnected together plays a major role in the noise performances of the detection systems. The geometry of a sensor is therefore critical and drives the ASIC design. The second part of the paper takes the geometry of the detector as a story line to explore different kinds of ASIC structures and architectures. From the simple single-channel ASIC for CCDs to the most advanced 3D ASIC prototypes used to build dead-zone free imaging systems, the paper reports on different families of circuits for spectro-imaging systems. It emphasizes a variety of designer choices, all around the word, in different space missions.
Caliste-SO are CdTe hybrid detectors that will be used as spectrometer units in the Spectrometer Telescope for Imaging X-rays (STIX) on-board the Solar Orbiter space mission. Each unit is placed below one collimator of this Fourier telescope to measure one visibility of the image in the 4-150 keV energy range, with a spectral resolution of 1 keV FWHM at 6 keV. The paper presents the scientific requirements, the design, the fabrication and the tests of the Caliste- SO devices before mounting them onto printed circuits boards. Spectral response was characterized on the 98 spacegrade units for various operating parameters. The devices will equip the different instrument validation models, including 32 units for the final instrument flight model to be launched in 2018.
We present design status of the Microchannel X-ray Telescope, the focussing X-ray telescope on board the Sino- French SVOM mission dedicated to Gamma-Ray Bursts. Its optical design is based on square micro-pore optics (MPOs) in a Lobster-Eye configuration. The optics will be coupled to a low-noise pnCCD sensitive in the 0.2{10 keV energy range. With an expected point spread function of 4.5 arcmin (FWHM) and an estimated sensitivity adequate to detect all the afterglows of the SVOM GRBs, MXT will be able to provide error boxes smaller than 60 (90% c.l.) arc sec after five minutes of observation.
The Microchannel X-Ray Telescope will be implemented on board the SVOM space mission to observe the afterglow of gamma-ray bursts and localize them with 2 arcmin precision. The optical system is based on microchannel plates assembling in Wolter-I configuration to focus the X-rays in the focal plane, like done for the MIXS telescope of the BepiColombo ESA mission. The sensor part is a 256 × 256 pixel pnCCD from the Max-Planck Institute for Extraterrestrial Physics for high resolution spectroscopy and high quantum efficiency over 0.2 – 10 keV energy range, based on the same technology and design as the eROSITA telescopes for the Russian-German SRG mission. CEA-Irfu (Saclay) is in charge of the design and the realization of the camera, including the focal plane, the calibration wheel, the front-end electronics, the structure housing for background shielding and the active cooling system. A prototype of the full detection chain and the acquisition system was set up. The paper presents the preliminary design of the electrical, mechanical and thermal architectures of the camera. It focuses on the fabrication and testing of the critical elements of the design and concludes on the on-going developments.
We have constructed a stacked detector system operating in the X-ray range from 0.5 keV to 250 keV that consists of a Si-based 64×64 DePFET-Matrix in front of a CdTe hybrid detector called Caliste-64. The setup is operated under laboratory conditions that approximate the expected environment of a space-borne observatory. The DePFET detector is an active pixel matrix that provides high count-rate capabilities with a near Fanolimited spectral resolution at energies up to 15 keV. The Caliste-64 hard X-ray camera consists of a 1mm thick CdTe crystal combined with very compact integrated readout electronics, constituting a high performance spectro-imager with event-triggered time-tagging capability in the energy range between 2 keV and 200 keV. In this combined geometry the DePFET detector works as the Low Energy Detector (LED) while the Caliste-64 - as the High Energy Detector (HED) - detects predominantly the high energetic photons that have passed the LED. In addition to the individual optimization of both detectors, we use the setup to test and optimize the performance of the combined detector system. Side-effects like X-ray fluorescence photons, electrical crosstalk, and mutual heating have negative impacts on the data quality and will be investigated. Besides the primary application as a combined imaging detector system with high sensitivity across a broad energy range, additional applications become feasible. Via the analysis of coincident events in both detectors we can estimate the capabilities of the setup to be used as a Compton camera and as an X-ray polarimeter - both desirable functionalities for use in the lab as well as for future X-ray missions.
Aline Meuris, Olivier Limousin, Olivier Gevin, Marie-Cécile Vassal, Fabrice Soufflet, Nicolas Fiant, Martin Bednarzik, Christopher Wild, Stefan Stutz, Guy Birrer, Claire Blondel, Isabelle Le Mer, Duc-Dat Huynh, Modeste Donati, Oliver Grimm, Volker Commichau, Gordon Hurford, Säm Krucker, François Gonzalez, Marc Billot
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.
KEYWORDS: Sensors, Device simulation, Photons, Field programmable gate arrays, Signal detection, Solar processes, X-rays, Temperature sensors, Data modeling, Data storage
The Spectrometer Telescope for Imaging X-rays (STIX) is one of 10 instruments on-board Solar Orbiter mission of the European Space Agency (ESA) scheduled to be launched in 2017. STIX is aimed to provide imaging spectroscopy of solar thermal and non-thermal hard X-ray emissions from 4 keV to 150 keV using a Fourier-imaging technique. The instrument employs a set of tungsten grids in front of 32 pixelized CdTe detectors. These detectors are source of data collected and analyzed in real time by Instrument Data Processing Unit (IDPU). In order to support development and implementation of on-board algorithms a dedicated detector hardware simulator is designed and manufactured as a part of Electrical Ground Support Equipment (EGSE) for STIX instrument. Complementary to the hardware simulator is data analysis software which is used to generate input data and to analyze output data. The simulator will allow sending strictly defined data from all detectors’ pixels at the input of the IDPU for further analysis of instrument response. Particular emphasis is given here to the simulator hardware design.
Konrad Skup, A. Cichocki, R. Graczyk, M. Michalska, M. Mosdorf, W. Nowosielski, P. Orleański, A. Przepiórka, K. Seweryn, M. Stolarski, M. Winkler, J. Sylwester, M. Kowalinski, T. Mrozek, P. Podgorski, A. Benz, S. Krucker, G. Hurford, N. Arnold, H. Önel, A. Meuris, O. Limousin, O. Grimm
KEYWORDS: Sensors, X-rays, Space operations, Attenuators, Imaging systems, X-ray imaging, Field programmable gate arrays, Control systems, Data processing, Electronics
The Spectrometer/Telescope for Imaging X-rays (STIX) is one of 10 instruments on board Solar Orbiter, an M-class
mission of the European Space Agency (ESA) scheduled to be launch in 2017. STIX applies a Fourier-imaging
technique using a set of tungsten grids in front of 32 pixelized CdTe detectors to provide imaging spectroscopy of solar
thermal and non-thermal hard X-ray emissions from 4 to 150 keV. These detectors are source of data collected and
analyzed in real-time by Instrument Data Processing Unit (IDPU). Besides the data processing the IDPU controls and
manages other STIX’s subsystems: ASICs and ADCs associated with detectors, Aspect System, Attenuator, PSU and
HK. The instrument reviewed in this paper is based on the design that passed the Instrument Preliminary Design Review
(IPDR) in early 2012 and Software Preliminary Design Review (SW PDR) in middle of 2012. Particular emphasis is
given to the IDPU and low level software called Basic SW (BSW).
Today it is widely recognised that a measurement of the polarization status of cosmic sources high energy emission is a
key observational parameter to understand the active production mechanism and its geometry. Therefore new
instrumentation operating in the hard X/soft γ rays energy range should be optimized also for this type of measurement.
In this framework, we present the concept of a small high-performance spectrometer designed for polarimetry between
100 and 1000 keV suitable as a stratospheric balloon-borne payload dedicated to perform an accurate and reliable
measurement of the polarization status of the Crab pulsar, i.e. the polarization level and direction. The detector with 3D
spatial resolution is based on a CZT spectrometer in a highly segmented configuration designed to operate as a high
performance scattering polarimeter. We discuss different configurations based on recent development results and
possible improvements currently under study. Furthermore we describe a possible baseline design of the payload, which
can be also seen as a pathfinder for a high performance focal plane detector in new hard X and soft gamma ray focussing
telescopes and/or advanced Compton instruments. Finally we present preliminary data from Montecarlo undergoing
studies to determine the best trade-off between polarimetric performance and detector design complexity.
A. Benz, S. Krucker, G. Hurford, N. Arnold, P. Orleanski, H.-P. Gröbelbauer, S. Klober, L. Iseli, H. Wiehl, A. Csillaghy, L. Etesi, N. Hochmuth, M. Battaglia, M. Bednarzik, R. Resanovic, O. Grimm, G. Viertel, V. Commichau, A. Meuris, O. Limousin, S. Brun, N. Vilmer, K. Skup, R. Graczyk, M. Stolarski, M. Michalska, W. Nowosielski, A. Cichocki, M. Mosdorf, K. Seweryn, A. Przepiórka, J. Sylwester, M. Kowalinski, T. Mrozek, P. Podgorski, G. Mann, H. Aurass, E. Popow, H. Önel, F. Dionies, S. Bauer, J. Rendtel, A. Warmuth, M. Woche, D. Plüschke, W. Bittner, J. Paschke, D. Wolker, H. Van Beek, F. Farnik, J. Kasparova, A. Veronig, I. Kienreich, P. Gallagher, D. Bloomfield, M. Piana, A. Massone, B. Dennis, R. Schwarz, R. Lin
The Spectrometer Telescope for Imaging X-rays (STIX) is one of 10 instruments on board Solar Orbiter, a confirmed Mclass mission of the European Space Agency (ESA) within the Cosmic Vision program scheduled to be launched in 2017. STIX applies a Fourier-imaging technique using a set of tungsten grids (at pitches from 0.038 to 1 mm) in front of 32 pixelized CdTe detectors to provide imaging spectroscopy of solar thermal and non-thermal hard X-ray emissions from 4 to 150 keV. The status of the instrument reviewed in this paper is based on the design that passed the Preliminary Design Review (PDR) in early 2012. Particular emphasis is given to the first light of the detector system called Caliste-SO.
The Wide Field Imager (WFI) of the International X-ray Observatory (IXO) is an X-ray imaging spectrometer based on a
large monolithic DePFET (Depleted P-channel Field Effect Transistor) Active Pixel Sensor. Filling an area of
10 x 10 cm2 with a format of 1024 x 1024 pixels it will cover a field of view of 18 arcmin. The pixel size of
100 x 100 μm2 corresponds to a fivefold oversampling of the telescope's expected 5 arcsec point spread function. The
WFI's basic DePFET structure combines the functionalities of sensor and integrated amplifier with nearly Fano-limited
energy resolution and high efficiency from 100 eV to 15 keV. The development of dedicated control and amplifier
ASICs allows for high frame rates up to 1 kHz and flexible readout modes. Results obtained with representative
prototypes with a format of 256 x 256 pixels are presented.
The Wide Field Imager (WFI) of the International X-ray Observatory (IXO) is an X-ray imaging spectrometer based on a
large monolithic DePFET (Depleted P-channel Field Effect Transistor) Active Pixel Sensor. Filling an area of
10 × 10 cm² with a format of 1024 × 1024 pixels it will cover a field of view of 18 arcmin. The pixel size of
100 × 100 μm² corresponds to a fivefold oversampling of the telescope's expected 5 arcsec point spread function. The
WFI's basic DePFET structure combines the functionalities of sensor and integrated amplifier with nearly Fano-limited
energy resolution and high efficiency from 100 eV to 15 keV. The development of dedicated control and amplifier
ASICs allows for high frame rates up to 1 kHz and flexible readout modes. Results obtained with representative
prototypes with a format of 256 × 256 pixels are presented.
In the frame of the hard X-ray Simbol-X observatory, a joint CNES-ASI space mission to be flown in 2014, a prototype
of miniature Cd(Zn)Te camera equipped with 64 pixels has been designed. The device, called Caliste 64, is a spectro-imager
with high resolution event time-tagging capability. Caliste 64 integrates a Cd(Zn)Te semiconductor detector with
segmented electrode and its front-end electronics made of 64 independent analog readout channels. This 1 × 1 × 2 cm3
camera, able to detect photons in the range from 2 keV up to 250 keV, is an elementary detection unit juxtaposable on its
four sides. Consequently, large detector array can be made assembling a mosaic of Caliste 64 units. Electronics readout
module is achieved by stacking four IDeF-X V1.1 ASICs, perpendicular to the detection plane. We achieved good noise
performances, with a mean Equivalent Noise Charge of ~65 electrons rms over the 64 channels. Time resolution is better
than 70 ns rms for energy deposits greater than 50 keV, taking into account electronic noise and technological dispersal,
which enables to reject background by anticoincidence with very low probability of error. For the first prototypes, we
chose CdTe detectors equipped with Al-Ti-Au Schottky barrier contacts because of their very low dark current and
excellent spectroscopic performances. So far, three Caliste 64 cameras have been realized and tested. When the crystal is
cooled down to -10°C, the sum spectrum built with the 64 pixels of a Caliste 64 sample results in a spectral resolution of
664 eV FWHM at 13.94 keV and 841 eV FWHM at 59.54 keV.
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