This paper reports on the performance changes in CdTe:Cl semiconductor X-ray detectors seen after irradiation with 50 MeV protons up to a fluence of 1.6 center dot 10(11)cm(-2). The rationale for the irradiation parameters is described. Performance was quantified before and after irradiations by obtaining X-ray spectra with a barium-133 radioactive source and detectors cooled to -20 degrees C. Energy resolutions, electron and hole drift lengths, and energy calibration parameters were extracted by fitting model spectra to the data. Ten crystals of dimension 10x10x1 mm(3) were used, with two each being irradiated to 20%, 40%, 60%, 80%, and 100% of the maximum fluence. Each crystal is pixelized and the eight large pixels of area 9.6mm(2) are analysed separately to allow estimation of uncertainties. The main observations are a strong decrease of the electron drift length and an increase of the electronic noise with fluence. The hole drift length shows a tendency to increase with fluence. A basic interpretation of some observations in terms of an increasing density of acceptor trap levels with fluence is given.

Aims. The Spectrometer Telescope for Imaging X-rays (STIX) on Solar Orbiter is a hard X-ray imaging spectrometer, which covers the energy range from 4 to 150 keV. STIX observes hard X-ray bremsstrahlung emissions from solar flares and therefore provides diagnostics of the hottest (⪆10 MK) flare plasma while quantifying the location, spectrum, and energy content of flare-accelerated nonthermal electrons. Methods. To accomplish this, STIX applies an indirect bigrid Fourier imaging technique using a set of tungsten grids (at pitches from 0.038 to 1 mm) in front of 32 coarsely pixelated CdTe detectors to provide information on angular scales from 7 to 180 arcsec with 1 keV energy resolution (at 6 keV). The imaging concept of STIX has intrinsically low telemetry and it is therefore well-suited to the limited resources available to the Solar Orbiter payload. To further reduce the downlinked data volume, STIX data are binned on board into 32 selectable energy bins and dynamically-adjusted time bins with a typical duration of 1 s during flares. Results. Through hard X-ray diagnostics, STIX provides critical information for understanding the acceleration of electrons at the Sun and their transport into interplanetary space and for determining the magnetic connection of Solar Orbiter back to the Sun. In this way, STIX serves to link Solar Orbiter’s remote and in-situ measurements.

STIX is the X-ray spectral imaging instrument on-board the Solar Orbiter space mission of the European Space Agency, and together with nine other instruments will address questions of the interaction between the Sun and the heliosphere. STIX will study the properties of thermal and accelerated electrons near the Sun through their Bremsstrahlung X-ray emission, addressing in particular the emission from flaring regions on the Sun. The design phase of STIX has been concluded. This paper reports the final flight design of the instrument, focusing on design challenges that were faced recently and how they were addressed.

Caliste-SO is a CdTe hybrid detector designed to be used as a spectrometer for a hard X-ray Fourier telescope. The imaging technique was implemented in the Yohkoh satellite in 1991 and the RHESSI satellite in 2002 to achieve arc-second angular resolution images of solar flares with spectroscopic capabilities. The next generation of such instruments will be the Spectrometer Telescope Imaging X-rays (STIX) on-board the Solar Orbiter mission adopted by the European Space Agency in 2011 for launch in 2017. The design and performance of Caliste-SO allows both high spectral resolution and high count rate measurements from 4 to 150keV with limited demands on spacecraft resources such as mass, power and volume (critical for interplanetary missions). The paper reports on the flight production of the Caliste-SO devices for STIX, describing the test facilities built-up in Switzerland and France. It illustrates some results obtained with the first production samples that will be mounted in the STIX engineering model.

The Spectrometer/Telescope for Imaging X-rays (STIX) is a remote sensing instrument on-board the ESA Solar Orbiter spacecraft. STIX is designated to the study of energetic phenomena in solar flares. A Fourier-imaging technique using tungsten grid collimators in front of CdTe pixel detectors is employed, covering the 4 to 150 keV energy range with a full-width-half maximum resolution around 1 keV at low energies.Acrorad CdTe detectors of 1mm thickness with a planar aluminum Schottky contact are used as basis for a subsequent patterning process into eight large pixels, four small pixels, and a guard ring. The patterning is done by means of microfabrication technologies. The area of the patterned sensor is 10x10mm(2).Test equipment has been developed for selecting the detectors with best performance prior to integration with the read-out system, and for qualification purposes. The set-up allows pixel-based dark current measurements at low temperatures. Pixel dark currents below 60 pA are needed to avoid excess noise in the read-out ASIC. The best pixels show dark currents below 10 pA at 300 V bias and -20 degrees C. Spectroscopic measurements with Ba-133 sources confirm the good performance.This paper briefly explains the mission context of the CdTe detectors and then gives details of the production and testing procedures. Typical results are shown, with emphasis on performance degradation studies from displacement damage by proton irradiation. This is expected to be the dominant degradation mechanism for this application.

The Spectrometer Telescope for Imaging X-rays (STIX) is an instrument on the Solar-Orbiter space mission that performs hard X-ray imaging spectroscopy of solar flares. It consists of 32 collimators with grids and 32 spectrometer units called Caliste-SO for indirect Fourier-transform imaging. Each Caliste-SO device integrates a 1cm2 CdTe pixel sensor with a low-noise low-power analog front-end ASIC and circuits for supply regulation and filtering. The ASIC named IDeF-X HD is designed by CEA/Irfu (France) whereas CdTe-based semiconductor detectors are provided by the Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute (Switzerland). The design of the hybrid, based on 3D Plus technology (France), is well suited for STIX spectroscopic requirements (1keV FWHM at 6keV, 4keV low-level threshold) and system constraints (4W power and 5kg mass). The performance of the sub-assemblies and the design of the first Caliste-SO prototype are presented.

Hard X-ray grating interferometry has shown promising results in phase and scattering imaging, as well as in metrology applications. Recently, the technique has been extended to two dimensions, recording the full phase gradient vector and a directional scattering signal. Here, we present a process for fabricating the key optical elements required for this technique: phase and absorption gratings with periods of few micrometers and high aspect ratios, with a particular focus on two-dimensional grating structures. The fabrication process is based on deep reactive ion etching in silicon and electroplating of gold.

We developed a simple two-step replication method to transfer arrays of high aspect ratio nanopillars into films of poly(l-d,l-lactic acid) (PLLA). Such structures are promising model surfaces for tissue engineering applications. From arrays of 1 μm high and 200 nm wide pillars produced with e-beam lithography and reactive ion etching negative replicas were first formed by polydimethylsiloxane (PDMS) casting. The final replicates were produced by solvent casting from 1% to 4% solutions of PLLA in chlorinated solvents on the PDMS templates. The silicon masters provide excellent stability and reusability, whereas the flexibility and low surface energy of the PDMS are necessary for the separation of the casts made with PLLA, a brittle material which is difficult to handle. AFM and SEM characterizations confirmed a high fidelity reproduction of the structures with aspect ratios of 1:5. In vitro tests using mouse neural stem cells seeded on nanopillars showed that the cells sense the nano-sized topography and respond accordingly by orienting themselves.

Phase-contrast imaging at laboratory-based x-ray sources using grating interferometers has been developed over the last few years for x-ray energies of up to 28 keV. Here, we show first phase-contrast projection and tomographic images recorded at significantly higher x-ray energies, produced by an x-ray tube source operated at 100 kV acceleration voltage. We find our measured tomographic phase images in good agreement with tabulated data. The extension of phase-contrast imaging to this significantly higher x-ray energy opens up many applications of the technique in medicine and industrial nondestructive testing.