The preservation of archaeological iron artefacts necessitates stabilization treatments. For this study, such treatments were applied, in aerated and deaerated NaOH solutions, to Roman iron bars excavated from a marine site in order to understand the evolution of corrosion layers composed of ferrous hydroxychloride beta-Fe-2(OH)(3)Cl. Their transformation was monitored in situ by micro-diffraction under synchrotron radiation and characterized ex situ using multi-scale complementary analytical tools. The formation of transient phases such as ferrous hydroxide Fe(OH)(2) was identified in both media and chlorinated green rust GR(Cl-) occurred in aerated solutions, showing the influence of dissolved oxygen on the transformation processes.

In order to fully benefit from a beam produced by modern synchrotron light sources, characterised by a wide and continuous energy spectrum, high brightness and a very high intensity, advancement in detector technology has been made over the last decades. However, one of the main limitations of the state-of-the-art counting hybrid pixel detectors is the maximum count-rate that is very often few orders of magnitudes lower than of the incident, reflected or diffracted beam flux. Therefore, direct beam attenuation is mandatory in order to perform the measurements according to the detector's characteristics. In this work we present a major upgrade of a fast attenuation system developed at Synchrotron SOLEIL, which allows for a dynamical change of the beam attenuation as a function of the photon flux received by XPAD S140 photon counting detector. The system performs a cyclic real-time estimation of the flux received by every pixel during acquisition of an image and searches for clusters of at least two pixels that exceed user defined levels of counts/s. The beam attenuation is immediately and automatically changed in order to guarantee that the detector will always operate in its linear range even during a long continuous scan, by acting on the direct attenuators.

The XPAD3 chip bump-bonded to a Si sensor has been widely used in preclinical micro-computed tomography and in synchrotron experiments. Although the XPAD3 chip is linear up to 60 keV, the performance of the XPAD3/Si hybrid detector is limited to energies below 30 keV, for which detection efficiencies remain above 20%. To overcome this limitation on detection efficiency in order to access imaging at higher energies, we decided to develop a camera based on XPAD3 single chips bump-bonded to high-Z CdTe sensors. We will first present the construction of this new camera, from the first tests of the single chip hybrids to the actual mechanical assembly. Then, we will show first images and stability tests performed on the D2AM beam line at ESRF synchrotron facility with the fully assembled camera.

We investigate the improvement from the use of high-Z CdTe sensors for pre-clinical K-edge imaging with the hybrid pixel detectors XPAD3. We compare XPAD3 chips bump bonded to Si or CdTe sensors in identical experimental conditions. Image performance for narrow energy bin acquisitions and contrast-to-noise ratios of K-edge images are presented and compared. CdTe sensors achieve signal-to-noise ratios at least three times higher than Si sensors within narrow energy bins, thanks to their much higher detection efficiency. Nevertheless Si sensors provide better contrast-to-noise ratios in K-edge imaging when working at equivalent counting statistics, due to their better estimation of the attenuation coefficient of the contrast agent. Results are compared to simulated data in the case of the XPAD3/Si detector. Good agreement is observed when including charge sharing between pixels, which have a strong impact on contrast-to-noise ratios in K-edge images.

The CHiPSpeCT consortium aims at building a large multi-modules CdTe based photon counting detector for hard X-ray applications. For this purpose, we tested nine XPAD3.2 single chip hybrids in various configurations (i.e. Ohmic vs. Schottky contacts or electrons vs. holes collection mode) in order to select the most performing and best suited configuration for our experimental requirements. Measurements have been done using both X-ray synchrotron beams and 241Am source. Preliminary results on the image quality, calibration, stability, homogeneity and linearity of the different types of detectors are presented.

A new experimental approach to perform in situ electric field diffraction on single crystals using an on-then-off pump–probe mode in situ ( i.e. the field-switching method) with a synchrotron or a laboratory X-ray source is presented. Taking advantage of the fast readout of the XPAD hybrid pixel two-dimensional detector and its programmable functionalities, the operation mode of the detector has been customized to significantly increase the efficiency of the method. The very weak electric field-induced structural response of a piezoelectric crystal can be accurately measured. This allows the piezoelectric tensor to be precisely obtained from Δθ shifts while the structural variations can be modelled using a full set of Δ I / I data. The experimental method and methodology are detailed and tested as a case study on pure piezoelectric compounds belonging to the α-quartz family (SiO 2 and GaAsO 4 single crystals). Using the two scan modes developed, it is demonstrated that tiny Bragg angle shifts can be measured as well as small field-induced Bragg intensity variations (<1%). The relevance of measurements performed with an X-ray laboratory source is demonstrated: partial data sets collected at synchrotrons can be completed, but more interestingly, a large part of the study can now be realized in the laboratory (medium to strong intensity reflections) in a comparable data collection time.

Shaping a YAG scintillator crystal into a truncated-ball lens enables to image with a high numerical aperture its front surface, where the image converted from x-rays to visible is localized. Hence, both resolution and luminosity gains can be expected. Moreover if the plane surface is set at the Young-Weierstrass point of the spherical refractive surface, stigmatic imaging is achieved. On this principle, we have constructed an imaging detector from a 10 mm diameter YAG:Ce sphere and a long working distance plane-apochromatic microscope objective which does not limit the numerical aperture. The effective numerical aperture of the built system is 1.08, giving a Rayleigh resolution limit of 0.3 mu m. Images of test objects (diatoms) have been recorded, in contact mode, with 103 eV. Periodic features of 0.4 mu m pitch are visible on these images. The field of view is close to 200 mu m. The device is intended as an aid for X-ray optics fine-tuning and characterization.

The XPAD3, a photon counting hybrid pixel detector developed in collaboration by SOLEIL Synchrotron, the Institut Neel and the Centre de Physique des Particules de Marseille (CPPM) [1], is now successfully used for a large variety of X-ray experiments on third generation synchrotron light sources [2]. Several 7.3 cm x 12.5 cm imagers composed of 8 silicon modules (7 chips per module, 9600 pixel of 130μm side per chip) are routinely used on different synchrotron beamlines at Soleil and on the CRG beamline D2AM at ESRF. Detector performances such as noiseless detection, high dynamic (27 bits) and fast framing rate (640 fps) have opened up the possibility of new or improved types of measurements. Nevertheless, above 15 keV, besides the loss of efficiency [2], the X-ray scattering in silicon sensor and the material located behind significantly increases the shape and the width of thepoint-spread function at 0.01% of the maximum. This effect prevents the study of low intensity phenomena such as diffuse scattering, which would be observed at the foot of theBragg peak and theoretically measurable with the large dynamic of the detector. This effect has been measured at different energies with monochromatic synchrotron beam (on CRISTAL and METROLOGIE Soleil beamlines) on a mono module Silicon XPAD and then compared with a Quad CdTe XPAD prototype (cf. figure 1). The results, which will be presented, demonstrate the superiority of the high Z sensor and push the investigation of the CdTe as a material sensor even at mid energy.

We present the first time-resolved pump-probe experiment performed at synchrotron SOLEIL at the CRISTAL diffraction beamline. The time-resolved setup will be used in the near future for sub-ns time resolution experiments. We studied spin state switching in a [TPA Fe(III) TCC] PF6 single crystal as induced by a approximate to 6 ns laser pulse (1064 nm), by measuring the 3D diffraction volume of the 002 Bragg reflection as a function of time after excitation. The intensity profiles (rocking curves) are found to evolve at two characteristic timescales, namely hundreds of ns and few mu s, exhibiting subtle profile changes and peak broadenings. Consistently with previous studies, we interpret these features as due to structural inhomogeneities related to laser-induced deformation wave propagation and heat diffusion, which both start from the absorbing sites.

The XPAD3 is the third generation of a single photon counting chip developed in collaboration by SOLEIL Synchrotron, the Institut Néel and the Centre de Physique de Particules de Marseille (CPPM). The chip contains 9600 pixels of 130 μm side and a counting electronic chain with an adjustable low level threshold in each pixel. Imaging and detection performance (detective quantum efficiency, modulation transfer function and energy resolution) of the XPAD3 detectors hybridized with Si and CdTe sensors have been evaluated and compared using monochromatic synchrotron X-rays beam. A second version of the chip, optimized for pump-probe experiments, has been realized and successfully tested. Three 7.3 cm x 12.5 cm Si-XPAD3 imagers, composed of 8 silicon modules (7 chips per module) and one 2.1 cm x 3.1 cm CdTe-XPAD3 imager (4 chips) have been constructed and successfully used for synchrotron diffraction experiments and biomedical imaging.

XPAD3 is a large surface X-ray photon counting imager with high count rates, large counter dynamics and very fast data readout. Data are readout in parallel by a PCI Express interface using DMA transfer. The readout frame rate of the complete detector comprising 0.5 MPixels amounts to 500 images per second without dead-time.

We present the development of an imager for the soft X-rays beamlines of synchrotron SOLEIL and the results obtained with this device. This imager, named DiagOn, is an alignment diagnostic tool intended to precisely define the emission axis of an undulator, that has been developed by SOLEIL synchrotron Detectors and Optics groups. It uses the particular structure of monochromatic undulator emission into a narrow hollow cone centered on the axis. One wavelength is selected by a multilayer mirror to produce a characteristic image of the emission cone on scintillator and CCD camera. This kind of imager is for the moment installed at four beamlines at SOLEIL, DESIRS, TEMPO, CASSIOPEE and PLEIADES. It allows for the determination of the position of the light emission axis, to align the elements of the beamline, and especially the front end diaphragms. But, furthermore, it can be used for the primary tests of the characteristics of the insertion device.

Using Si sensors, the XPAD3 chip can be used from 4 up to 25 keV. The CdTe detector was designed to improve efficiency at higher energies (60 keV), but it still works at low energy: data were collected at 8 keV. Firstly, small detector prototypes were built and used for scattering experiments at BM02/ESRF and DIFABS/SOLEIL. Comparisons were made by collecting small angle X-ray scattering data using the same settings with the XPAD3 and the beam line CCD camera, as well as diffuse scattering from a quasi-crystal. Finally, a surface diffraction experiment was performed to characterize the strain in a few layers of GaInAs epitaxially grown on a GaAs single crystal.

A 20kpixels CdTe sensor has been hybridized on XPAD3S CMOS photon-counting chips, forming a 19,200pixels imaging device. P-type CdTe with rectifying contact has been employed. This sensor works in hole collection mode with a pulse shaping time of about 150ns. Detector construction and operation are described, and first results obtained with 241Am source as well as diffraction images using an X-ray synchrotron beam are presented. Polarization effects are present, but remain at a very manageable level.

Results obtained using a hybrid pixel photon-counting detector in powder diffraction experiments are presented. The detector works at room temperature and its dynamic response ranges from 0.01 photons pixel(-1) s(-1) up to 10(6) photons pixel(-1) s(-1). The pixel sizes are 0.33 mm x 0.33 mm for a total area of 68 mm x 68 mm. On recording high-resolution diffraction patterns of powders, a reduction of the experimental time by more than a factor of 20 is obtained without loss of data quality. The example of an X-zeolite shows that such detectors can be used for very demanding anomalous experiments. In situ experiments of quenching liquid oxides show that frames of 0.01 s can be achieved for studying such processes.

The sensitivity for detection of two special nuclear materials, /sup 235/U and /sup 239/Pu, using an advanced high-pressure xenon detector (HPXe) and robust fitting analysis (RFA) with RobWin is experimentally determined for a set of collections with varying attenuation thicknesses of lead. These measurements provide essential information that enables comparisons with other detector systems for nuclear portal monitoring applications. Advantages of the combined use of HPXe and RFA for nuclear portal monitors are discussed, and recent progress with them is described briefly. An experiment designed to provide data from which models for nuclear portal monitor design can be grounded is described. Spectra were collected at CEA/Saclay with an HPXe unit from MEPhI for both /sup 235/U and /sup 239/Pu With attenuating thicknesses of lead ranging from zero to four millimeters. A single analysis procedure that yielded consistent results for all spectra was developed to simulate the automated application of analysis without user intervention and without advance knowledge of shielding thickness. These two spectrum series were then analyzed with RFA methodology for detection sensitivity and is reported in a form that can be used for comparison with other detector systems and for optimization of design parameters for HPXe/RFA portal monitor systems.