The detector system of the X-Ray Integral Field Unit (X-IFU), one of the two ATHENA focal plane instruments will be an ambitious step forward in the field of astronomical X-ray detection. We describe its baseline configuration, consisting of 3840 Transition Edge Sensors (TES) microcalorimeters with an energy resolution of 2.5 eV FWHM, spanning a 5 arcminute field-of-view and allowing an imaging resolution of 5 arcsec. The detectors are read out in 96 channels of 40 pixels each, using frequency domain multiplexing (FDM). Each channel contains a dual-stage SQUID pre-amplifier and a low-noise amplifier (LNA). In order to enhance the dynamic range of the SQUIDs a specific technique, baseband feedback (BBFB), is applied. The generation of the carrier and feedback signals, and the signal processing are done in the digital domain. We review the requirements for the main elements of this system, needed to ensure the high performance of the detector system. From the resolution requirements for the detectors follows a budget for contributions to the energy resolution on top of the intrinsic detector resolution. This budget forms the basis for the assessment of the dynamic range requirements for the SQUID and the LNA and the DACs and the ADC. Requirements are also derived for the levels of crosstalk and non-linearity in the readout chain.
One of the instruments on the Advanced Telescope for High-Energy Astrophysics (Athena) which was one of the three
missions under study as one of the L-class missions of ESA, is the X-ray Microcalorimeter Spectrometer (XMS). This
instrument, which will provide high-spectral resolution images, is based on X-ray micro-calorimeters with Transition
Edge Sensor (TES) and absorbers that consist of metal and semi-metal layers and a multiplexed SQUID readout. The
array (32 x 32 pixels) provides an energy resolution of < 3 eV. Due to the large collection area of the Athena optics, the XMS instrument must be capable of processing high counting rates, while maintaining the spectral resolution and a low deadtime. In addition, an anti-coincidence detector is required to suppress the particle-induced background. Compared to the requirements for the same instrument on IXO, the performance requirements have been relaxed to fit into the much more restricted boundary conditions of Athena.
In this paper we illustrate some of the science achievable with the instrument. We describe the results of design studies for the focal plane assembly and the cooling systems. Also, the system and its required spacecraft resources will be given.
One of the instruments on the International X-ray Observatory (IXO), under study with NASA, ESA and JAXA, is the
X-ray Microcalorimeter Spectrometer (XMS). This instrument, which will provide high spectral resolution images, is
based on X-ray micro-calorimeters with Transition Edge Sensor thermometers. The pixels have metallic X-ray absorbers
and are read-out by multiplexed SQUID electronics. The requirements for this instrument are demanding. In the central
array (40 x 40 pixels) an energy resolution of < 2.5 eV is required, whereas the energy resolution of the outer array is
more relaxed (≈ 10 eV) but the detection elements have to be a factor 16 larger in order to keep the number of read-out
channels acceptable for a cryogenic instrument. Due to the large collection area of the IXO optics, the XMS instrument
must be capable of processing high counting rates, while maintaining the spectral resolution and a low deadtime. In
addition, an anti-coincidence detector is required to suppress the particle-induced background.
In this paper we will summarize the instrument status and performance. We will describe the results of design studies for
the focal plane assembly and the cooling systems. Also the system and its required spacecraft resources will be given.
We describe the optimization of transition edge superconducting
(TES) detectors for use in a far-infrared (FIR) Fourier transform spectrometer (FTS) mounted on a cryogenically cooled space-borne telescope (e.g. SPICA). The required noise equivalent power (NEP) of the detectors is approximately 10-19W/√Hz in order to be lower than the photon noise from astrophysical sources in octave wide bands in the FIR. The detector time constants must be less than 10 ms in order to allow fast scanning of the FTS mechanism. The detectors consist of superconducting thermometers suspended on thin legs of thermally isolating silicon nitride and operate at a temperature of approximately 100 mK. We present the design of the detectors, a proposed focal plane layout and optical coupling scheme and measurements of thermal conductance and time constant for low NEP prototype TES bolometers.
This paper describes the focal plane instrumentation of the XEUS mission as proposed for ESA's Cosmic Vision
program. Each of the instruments is described in some detail with its performance characteristics given. The
development status of the instrument complement and the items requiring further development are indicated.
The EURECA (EURopean-JapanEse Calorimeter Array) project aims to demonstrate the science performance and
technological readiness of an imaging X-ray spectrometer based on a micro-calorimeter array for application in future
X-ray astronomy missions, like Constellation-X and XEUS. The prototype instrument consists of a 5 × 5 pixel array of
TES-based micro-calorimeters read out by by two SQUID-amplifier channels using frequency-domain-multiplexing
(FDM). The SQUID-amplifiers are linearized by digital base-band feedback. The detector array is cooled in a cryogenfree
cryostat consisting of a pulse tube cooler and a two stage ADR. A European-Japanese consortium designs,
fabricates, and tests this prototype instrument. This paper describes the instrument concept, and shows the design and
status of the various sub-units, like the TES detector array, LC-filters, SQUID-amplifiers, AC-bias sources, digital
electronics, etc.
Initial tests of the system at the PTB beam line of the BESSY synchrotron showed stable performance and an X-ray
energy resolution of 1.58 eV at 250 eV and 2.5 eV @ 5.9 keV for the read-out of one TES-pixel only. Next step is
deployment of FDM to read-out the full array. Full performance demonstration is expected mid 2009.
How structures of various scales formed and evolved from the early Universe up to present time is a fundamental
question of astrophysics. EDGE will trace the cosmic history of the baryons from the early generations of massive
stars by Gamma-Ray Burst (GRB) explosions, through the period of galaxy cluster formation, down to the very low
redshift Universe, when between a third and one half of the baryons are expected to reside in cosmic filaments undergoing
gravitational collapse by dark matter (the so-called warm hot intragalactic medium). In addition EDGE, with its
unprecedented capabilities, will provide key results in many important fields. These scientific goals are feasible with a
medium class mission using existing technology combined with innovative instrumental and observational capabilities
by: (a) observing with fast reaction Gamma-Ray Bursts with a high spectral resolution (R ~ 500). This enables the study
of their (star-forming) environment and the use of GRBs as back lights of large scale cosmological structures; (b)
observing and surveying extended sources (galaxy clusters, WHIM) with high sensitivity using two wide field of view
X-ray telescopes (one with a high angular resolution and the other with a high spectral resolution). The mission concept
includes four main instruments: a Wide-field Spectrometer with excellent energy resolution (3 eV at 0.6 keV), a Wide-
Field Imager with high angular resolution (HPD 15") constant over the full 1.4 degree field of view, and a Wide Field
Monitor with a FOV of 1/4 of the sky, which will trigger the fast repointing to the GRB. Extension of its energy response
up to 1 MeV will be achieved with a GRB detector with no imaging capability. This mission is proposed to ESA as part
of the Cosmic Vision call. We will briefly review the science drivers and describe in more detail the payload of this
mission.
XEUS is the potential successor to ESA's XMM-Newton X-ray observatory and is being proposed in response to the Cosmic Vision 2015-2025 long term plan for ESA's Science Programme. Novel light-weight optics with an effective area of 5 m2 at 1 keV and 2 m2 at 7 keV and 2-5" HEW spatial resolution together with advanced detectors will provide much improved imaging, spectroscopic and timing performances and open new vistas in X-ray astronomy in the post 2015 timeframe. XEUS will allow the study of the birth, growth and spin of the super-massive black holes in early AGN, allow the cosmic feedback between galaxies and their environment to be investigated through the study of inflows and outflows and relativistic acceleration and allow the growth of large scale structures and metal synthesis to be probed using the hot X-ray emitting gas in clusters of galaxies and the warm/hot filamentary structures observable with X-ray absorption spectroscopy. High time resolution studies will allow the Equation of State of supra-nuclear material in neutron stars to be constrained. These science goals set very demanding requirements on the mission design which is based on two formation flying spacecraft launched to the second Earth-Sun Lagrangian point by an Ariane V ECA. One spacecraft will contain the novel high performance optics while the other, separated by the 35 m focal length, will contain narrow and wide field imaging spectrometers and other specialized instruments.
EURECA (EURopean-JapanEse Calorimeter Array) comprises a 5 x 5 pixel imaging TES-based micro-calorimeter
array read-out by SQUID-based frequency-domain-multiplexed electronics and cooled down by an adiabatic
demagnetization refrigerator. A European-Japanese consortium designs, fabricates, and tests this prototype instrument
with the aim to show within about 2 years technology readiness of a TES-based X-ray imaging micro-calorimeter array
in anticipation of future X-ray astronomy missions, like XEUS (ESA), Constellation-X (NASA), NEXT (JAXA), DIOS
(JAXA), ESTREMO (ASI), and NEW (Dutch-multinational). This paper describes the instrument concept, and shows
the design of the various sub-units, like the TES detector array, LC-filters, SQUID-amplifiers, flux-locked-loop
electronics, AC-bias sources, etc.
The most recent observations of the cosmic microwave background (e.g., WMAP) show that baryons contribute about 4% to the total density of the Universe. However at redshift less than or equal to 1, about half of these baryons have not yet been observed. Cosmological simulations predict that these "missing" baryons should be distributed in filaments, have temperatures of 105 to 107 K and overdensities of a few to hundred times the average baryon density, forming the so-called Warm-Hot Intergalactic Medium (WHIM). There is increasing evidence from Chandra and XMM-Newton that the WHIM may indeed exist. However it is clear that to map the morphology of the WHIM and to measure its physical conditions, a completely different class of instruments is required. Measuring the WHIM in emission in the soft X-ray band is a promising option. To detect the relatively weak, extended emission of the WHIM, the instrument should have a large grasp (collecting area times field of view), and an energy resolving power of about 500 at 1 keV is required to separate the emission of these large scale filaments from foreground emission.
We discuss a design that includes X-ray mirrors in combination with a large 2D cryogenic detector, which will allow us to map a significant fraction of this gas. Such detector and its read-out based on Frequency Domain Multiplexing, are currently under development at SRON. It seems feasible to build an array of 24 x 24 pixels of TES microcalorimeters with good energy resolution (few eV). This detector will be combined with a mirror design which is based on 2 and 4 reflections and gives a large area (> 500 cm2) over a relatively large field of view. A preliminary study of the mission concept indicates that this can be implemented in a relatively small satellite (total weight 650 kg). While the main goal of this satellite will be to map and study the physical properties of the missing baryons, the instrument's large area and large field of view will also result in major progress in related fields.
A very significant fraction of the baryonic matter in the local universe is predicted to form a Warm Hot Intergalactic Medium (WHIM) of very low density, moderately hot gas, tracing the cosmic web. Its X-ray emission is dominated by metal features, but is weak (< 0.01 photons/cm2/s/sr) and potentially hard to separate from the galactic component. However, a mission capable of directly mapping this component of the large scale structure of the universe, via a small number of well chosen emission lines, is now within reach due to recent improvements in cryogenic X-ray detector energy resolution. To map the WHIM, the energy resolution and grasp are optimized. A number of missions have been proposed to map the missing baryons including MBE (US/SMEX program) and DIOS (Japan). The design of the mirror and detector have still room for improvements which will be discussed. With these improvements it is feasible to map a 10 x 10 degree area of the sky in 2 years out to z = 0.2 with sufficient sensitivity to directly detect WHIM structure, such as filaments connecting clusters of galaxies. This structure is predicted by the current Cold Dark Matter paradigm which thus far appears to provide a good description of the distribution of matter as traced by galaxies.
NbN hot electron bolometer (HEB) mixers are at this moment the best heterodyne detectors for frequencies above 1 THz. However, the fabrication procedure of these devices is such that the quality of the interface between the NbN superconducting film and the contact structure is not under good control. This results in a contact resistance between the NbN bolometer and the contact pad. We compare identical bolometers, with different NbN - contact pad interfaces, coupled with a spiral antenna. We find that cleaning the NbN interface and adding a thin additional superconductor prior to the gold contact deposition improves the noise temperature and the bandwidth of the HEB mixers with more than a factor of 2. We obtain a DSB noise temperature of 950 K at 2.5 THz and a Gain bandwidth of 5-6 GHz. For use in real receiver systems we design small volume (0.15x1 micron) HEB mixers with a twin slot antenna. We find that these mixers combine good sensitivity (900 K at 1.6 THz) with low LO power requirement, which is 160 - 240 nW at the Si lens of the mixer. This value is larger than expected from the isothermal technique and the known losses in the lens by a factor of 3-3.5.
The ESA mission XMM-Newton was launched in 1999. Two of the three X-ray telescopes include reflection grating spectrometers (RGS). These spectrometers consist of a set of reflection gratings and an array of 9 back-illuminated CCDs, optimized for the soft energy response (0.35 - 2 keV). These CCDs can be passively cooled between -80 and -120°C. After a short description of the instrument we compare the performance of these CCD detectors with the pre-flight expectations and discuss the effect of some design choices on the in-flight performance. We concentrate on the effects of radiation damage due to cosmic rays and coronal mass ejections of the Sun, including flickering pixels and the effects of cooling the detector to -110°C. We also address the stability of the detector response including the assessment of possible contamination of these cooled detectors.
Piet de Korte, John van Baar, Norman Baars, Frank Bakker, Wouter Bergmann Tiest, Marcel Bruijn, Alexander Germeau, Henk Hoevers, Mikko Kiviranta, Eric Krouwer, Jan van der Kuur, Marco Lubbers, Wim Mels, Marcel Ridder, Heikki Seppae, Remco Wiegerink
A micro-calorimeter array with superconducting transition-edge sensors read out by a SQUID-based frequency-domain multiplexer is under development for the X-ray imaging spectrometer on board ESA’s X-ray Evolving Universe Spectroscopy (XEUS) mission. The XEUS requirements are 2 and 5 eV FWHM energy resolution for 2 and 7 keV X-rays, respectively. An array of 32 x 32 pixels with 250 micron square pixels is envisaged. SRON and MESA+ have developed 5 x 5 imaging micro-calorimeter prototype arrays along a bulk micromachining and a surface micromachining route. The present state of array design and development with emphasis on pixel-to-pixel performance measurements of thermal and I-V characteristics, sensor noise and energy resolution are presented. SRON and VTT are developing frequency-domain multiplexing with SQUID current amplifiers to read out the 32 x 32 array. The concept for the frequency division multiplexing read-out will be presented and its performance characteristics discussed. Recent results of sensor operation under AC-bias (500 kHz) are presented.
The high-energy response of XEUS will be of crucial importance for a number of astrophysical topics, e.g.: highly obscured AGNs, non-thermal emissions from SNRs, AGNs and clusters of galaxies, nuclear line emission from SNRs and hard X-ray emission in GRB afterglows. The XEUS telescope will achieve high-energy response (up to 90 keV) employing super mirror technology whereby the inner mirrors will be coated with graded multi layers. The detectors will be implemented as part of the Wide Field Imager which also has DEPFET and CCDs to cover the soft-X-ray survey science. Solutions for the associated focal plane Hard X-ray Imaging Camera have been investigated by the XEUS Instrument Working Group and will be discussed in the present contribution.
Development of single pixel x-ray microcalorimeters at our institutes, employing superconducting-to-normal phase transition thermometers operating at about 100 mK, generally called Transition-Edge-Sensors (TES), has now resulted in an energy resolution of 3.9 eV FWHM for 5.89 keV x-rays in combination with a response time of 100 μs. Pixel arrays of these detectors, presently under development, will allow for unprecedented x-ray spectroscopy of spatially extended cosmic x-ray sources such as clusters of galaxies, supernova remnants, the galactic diffuse x-ray background and the arm-hot intergalactic medium. Optimization of these cryogenic imaging detectors around 1 keV, in combination with large-area x-ray optics, makes them the most suitable sensor for study of the formation and evolution of hot matter in the universe at large redshift. This detector concept is therefore included in the model payload of the XEUS mission, presently under study by ESA and ISAS. Smaller scale low energy x-ray spectroscopy missions could however generate significant progress in the understanding of supernova remnants, cluster of galaxies and galactic and intergalactic diffuse x-ray emission. This paper presents some science cases, which make explicit use of the unique combination of high efficiency, high spectral resolution and imaging of cryogenic x-ray imaging spectrometers. Furthermore it discusses the present development status of these imaging spectrometers at our institutes, their operating principles and expected performance figures.
We summarize our research activities on THz Nb diffusion-cooled hot electron bolometer (HEB) mixers, carried out at Space Research Organization Netherlands (SRON) and Delft University of Technology. This paper will include our understanding on the device physics of diffusion-cooled HEB mixers, noise and IF bandwidth measurements of waveguide mixers around 0.7 THz, and in particular recent measurements of Nb quasi-optical mixers at 0.64 and 2.5 THz. The waveguide devices demonstrate a receiver noise temperature of 900 K at 0.7 THz. The quasi-optical mixers show 1200 K at 0.64 THz and 4500 K at 2.5 THz and a maximum IF bandwidth of at least 5 GHz.
We report on the development of an imaging detector with high energy resolution for the X-ray Evolving Universe Spectroscopy Mission (XEUS). The type of detector we are studying is a voltage biased superconducting transition edge microcalorimeter, operated at sub-Kelvin temperatures. Baseline for the imaging function is an array of these calorimeters, read out using SQUID amplifiers. Based on the performance of and experience with single-pixel micro calorimeters, we discuss new design concepts and read-out of imaging arrays of micro calorimeters. Critical design elements are the thermal transport from the pixels to the bath, operating temperature and cross talk. The requirements of a SQUID read-out system for the XEUS spectrometer are addressed and the areas where development is needed are identified.
A feasibility study of an imaging 32 by 32 pixel micro- calorimeter array, intended for the XEUS mission is presented. Three different concepts, theoretically leading to a detector that combines an energy resolution of 5 eV for 8 keV x-rays and a count rate of at least 100 counts/pixel, are presented and discussed. The starting point for this study is the current progress in the field of single pixel micro-calorimeters employing voltage biased transition edge sensors. The design concepts originate from different philosophies for the thermal design and geometrical lay-out and will use state of the art micro-machining and lithography. Moreover, both from an electrical and a cooling point of view SQUID read-out will be the challenge and grouping of pixels might be considered.
The requirement set for the focal plane instruments on XEUS area addressed. The rationale for the selection of three focal plane instruments, a wide field imager with modest spectral resolution and tow narrow field imagers with high spectral resolution, is given. The principles and designs of all three instrument are shortly explained and their expected performances given. The cooling of the focal plane instruments, based on mechanical cryocoolers, is described as well.
Hot-electron bolometers have wide applicability. Both IR bolometers as well as x-ray micro-calorimetric are currently being developed by the Space Research Organization Netherlands. The IR bolometers are equipped with space impedance matched spider web absorbers. The detectors have voltage biased superconducting transition edge thermometers. When operated in the negative feedback regime, their response time is appreciably reduced. As will be shown, electrical test give a wealth of information on the bolometer performance. In this paper typical bolometer parameters such as current-voltage characteristics, time constants and noise equivalent power are described. Electrical test results are presented. For an IR bolometer a loop gain of 500 combined with an electrical NEP of 2 by 10-17 W/(root)Hz has been realized.
SFINX (SRON's Fabry-perot INterferometer eXperiment) consists of a 65 - 90 micrometer wavelength spectrometer based on a Fabry-Perot interferometer, and is equipped with both a conventional Ge:Ga photon detector operating at 4 K, and a novel high-temperature superconductor (HTS) bolometer detector operating at 87 K. The spectral resolution is about 8000, or 0.015 cm-1, comparable with the width of the thermal emission lines of the stratospheric species under study. Target molecules are OH, HCl, HO2, and possibly more. The SFINX instrument now under development will fly as a piggy-back instrument on a stratospheric balloon together with the MIPAS-B2 instrument of IMK/FZK (Karlsruhe, Germany), and can be regarded as a proof of concept for a satellite application. Because of its low satellite resource demands, for a satellite application a SFINX like instrument has great advantages with respect to Fourier transform spectrometers or heterodyne receivers. In particular, the HTS bolometer detector can be cooled by mechanical coolers which are presently available in space- qualified versions, thereby avoiding the use of liquid cryogen.
The x-ray multi-mirror (XMM) mission is the second of four cornerstone projects of the ESA long-term program for space science, Horizon 2000. The payload comprises three co- aligned high-throughput, imaging telescopes with a FOV of 30 arcmin and spatial resolution less than 20 arcsec. Imaging CCD-detectors (EPIC) are placed in the focus of each telescope. Behind two of the three telescopes, about half the x-ray light is utilized by the reflection grating spectrometer (RGS). The x-ray instruments are co-aligned and measure simultaneously with an optical monitor (OM). The RGS instruments achieve high spectral resolution and high efficiency in the combined first and second order of diffraction in the wavelength range between 5 and 35 angstrom. The design incorporates an array of reflection gratings placed in the converging beam at the exit from the x-ray telescope. The grating stack diffracts the x-rays to an array of dedicated charge-coupled device (CCD) detectors offset from the telescope focal plane. The cooling of the CCDs is provided through a passive radiator. The design and performance of the instrument are described below.
Superconductive tunnel junctions (STJs) are being developed as high energy resolution x-ray single photon detectors. Quasi-particle losses at the edges of such devices form a serious source of energy resolution degradation. A simple analytical relation for this source of resolution degradation has been derived from classical diffusion theory. Analyzing the x-ray spectra obtained for different series of STJs with various sizes, the edge reflectivity and the diffusion constant for our sputtered Nb films can be derived. This reflectivity can be explained by quasi- particle trapping. In addition progress is reported on the surface conditioning of single crystal, superconducting, Ta and Nb absorbers to be used for a highly efficient imaging x-ray spectrometer employing STJs as read-out.
Back-illuminated CCDs with high quantum efficiency in the soft x-ray range have been developed by EEV in collaboration with the Space Research Organization of the Netherlands (SRON) and the European Space Agency (ESA). These CCDs will be used as detector for the reflection grating spectrometer on board of the ESA x-ray multi-mirror mission XMM. To cover the full image of the reflection grating spectrometer an array of 9 CCDs along the Rowland circle with minimum dead space between the adjacent CCDs is needed. To obtain a high quantum efficiency over the full energy range (0.35 to 2.3 keV) the CCDs are illuminated from the backside. This requires a thin (approximately 50 nm) and homogeneous passivated layer at the backside, which is obtained by gas immersion laser doping. In addition a thin Al layer is deposited on the backside to reduce the sensitivity of the CCDs for visible/UV light. The technical aspects of the production of these CCDs as well as their calibration are discussed.
A review of the development status of high-Ta transition edge thermometer bolometers is given with emphasis
on the excess HTS film noise. It is shown that Si3N4 membrane technology should enable the production of
1 x 1 mm2 size bolometers with a Noise Equivalent Power (NEP) smaller than 3 x 1O_12 w/4f.
In this contribution we shortly review the current Fabry-Perot concept for remote sensing of stratospheric OH and in
more detail a number of sensitivity aspects. In this context the following topics will be addressed: imaging aspects,
instrument throughput and signal to noise optimisation, diffraction and the application of small detector arrays instead of
an image slicer. A separate paper is given on the review and optimisation of bolometric detectors.
X-ray calibration of the Electro-Optical Breadboard Model (EOBB) of the XMM Reflection Grating Spectrometer has been carried out at the Panter test facility in Germany. The EOBB prototype optics consisted of a four-shell grazing incidence mirror module followed by an array of eight reflection gratings. The dispersed x-rays were detected by an array of three CCDs. Line profile and efficiency measurements were made at several energies, orders, and geometric configurations for individual gratings and for the grating array as a whole. The x-ray measurements verified that the grating mounting method would meet the stringent tolerances necessary for the flight instrument. Post EOBB metrology of the individual gratings and their mountings confirmed the precision of the grating boxes' fabrication. Examination of the individual grating surface's at micron resolution revealed the cause of anomalously wide line profiles to be scattering due to the crazing of the replica's surface.
The Reflection Grating Spectrometer (RGS) onboard the ESA satellite XMM (X-ray Multi Mirror mission) combines a high resolving power (approximately 400 at 0.5 keV) with a large effective area (approximately 200 cm2). The spectral range selected for RGS (5 - 35 angstroms) contains the K shell transitions of N, O, Ne, Mg, Al, Si and S as well as the important L shell transitions of FE. The resolving power allows the study of a wide variety of challenging scientific questions. Detailed temperature diagnostics are feasible as the ionization balance is a unique function of the distribution of the electron temperature. Density diagnostics are provided by studying He-like triplets where the ratio of the forbidden to intercombination lines varies with density. Other fields of interest include the determination of elemental abundances, the study of optical depth effects, velocity diagnostics by measuring Doppler shifts and the estimate of magnetic fields through the observation of Zeeman splitting. The resolving power is obtained by an array of 240 gratings placed behind the mirrors of the telescope, dispersing about half of the X-rays in two spectroscopic orders. The X-rays are recorded by an array of 9 large format CCDs. These CCDs are operated in the frame transfer mode. They are back illuminated as the quantum efficiency of front illuminated devices is poor at low energies because of their poly-silicon gate structure. To suppress dark current the CCDs are passively cooled. In order to obtain the effective area of about 200 cm2, grating arrays and CCD cameras are placed behind two of the three XMM telescopes. A model of RGS was tested last autumn ('93) at the Panter long beam X-ray facility in Munich. The model consisted of a subset of four mirrors, eight representative gratings covering a small section of the inner mirror shells and a CCD camera containing three CCDs. The purpose of these tests was to verify the resolution and sensitivity of the instrument as a function of X-ray energy. Extensive simulations, using a Monte Carlo raytracing code, are used to interpret these tests. Preliminary results of these tests will be discussed and compared to the calculated response.
Superconductive tunneljunctions are under development as detectors for X-ray astronomy in the 0.5-10 keV energy range, because of their potentially high energy resolution (E < 10 eV) in combination with high detection efficiency. Especially absorber-junction combinations offer the prospect of high energy resolution detectors with a high detection efficiency and a reasonable ( 1 cm2) size. The proximity effect between the Nb absorber and the Al trapping layer plays a dominant role. A study of the proximity effect in Nb/Al/Al2 03/Al/Nb junctions with different Al-layer, the trapping layer, thicknesses is presented
The European Space Agency X-ray Multi-Mirror mission will be devoted to X-ray imaging and spectroscopy with high throughput. Both the EPIC focal plane camera instrument, and the RGS dispersive spectrometer require detectors with high sensitivity in the soft X-ray waveband. A description of
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