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Redox-active heteropolyanions are widely applied to redox catalysts and electron acceptors and the understanding of their reduced states in solution is essential. In this study, the structural changes of Keggin-type tungstophosphate: [PW 12 O 40 ]3− induced by electrochemical reduction were investigated using W L 3 -edge X-ray absorption near-edge structure (XANES) spectra in high-energy-resolution fluorescence detection (HERFD) mode. W L 3 -edge HERFD-XANES spectra revealed the changes in the electronic state of W species and local structure of {WO 6 } units, which were negligible in conventional transmittance mode; the peak intensities of the split two white line peaks were switched by the electrochemical reduction accompanied by enlargement of the splitting width. Our findings suggest that the injected electron was delocalized on whole {WO 6 } units in [PW 12 O 40 ]3− and that the improved symmetry of {WO 6 } units compensated for the change in valence due to the injected electron. [ABSTRACT FROM AUTHOR]

4H-SiC Schottky photodiodes, with 25 μ m epitaxial layers, employing thin (20 nm) Ni 2 Si Schottky contacts, were investigated for high temperature photon counting X-ray spectroscopy. Important X-ray photodiode detector parameters were extracted from electrical characterization within the temperature range 160 °C to 0 °C. The devices were found to be fully depleted at an applied electric field of 20 kV/cm; a leakage current density of 33 nA cm -2 ± 1 nA cm−2 at 160 °C, was measured for one of the devices. The detectors were subsequently connected to low-noise photon counting readout electronics and investigated for their spectral performance at temperatures up to 100 °C. With the charge-sensitive preamplifier operated at the same temperature as the detector the best energy resolution (Full Width at Half Maximum at 5.9 keV) obtained decreased from 2.20 keV ± 0.04 keV (120 e − rms ± 2 e − rms) at 100 ∘ C to 1.20 keV ± 0.03 keV (65 e - rms ± 2 e − rms) at 0 ∘ C. The dominant source of noise broadening the 55Fe X-ray photopeak was found to be the dielectric noise, except for the spectra accumulated at 100 °C and long shaping times (> 6 μ s), in those case the main source of photopeak broadening was the white parallel noise. [ABSTRACT FROM AUTHOR]

In past years efforts have concentrated on the development of arrays of Silicon Drift Detectors for X-ray spectroscopy. This is in stark contrast to the little effort that has been devoted to the improvement of germanium detectors, in particular for synchrotron applications. Germanium detectors have better energy resolution and are more efficient in detecting high energy photons than silicon detectors. In this context, the detector consortium of the European project LEAPS-INNOV has set an ambitious R&D program devoted to the development of a new generation of multi-element monolithic germanium detectors for X-ray detection. In order to improve the performance of the detector under development, simulations of the different detector design options have been performed. In this contribution, the efforts in terms of R&D are outlined with a focus on the modelization of the detector geometry and first performance results. These performance results show that a signal-to-background ratio larger than 1000 can be achieved in the energy range of interest from 5 keV to 100 keV. [ABSTRACT FROM AUTHOR]

Five SiC Schottky photodiodes for X-ray detection have been electrically characterized at room temperature. One representative diode was also electrically characterized over the temperature range 20°C to 140 °C. The performance at 30 °C of all five X-ray detectors, in both current mode and for photon counting X-ray spectroscopy was investigated. The diodes were fabricated in an array form such that they could be operated as either a 2×2 or 1×3 pixel array. Although the devices showed double barrier heights, high ideality factors and higher than expected leakage current at room temperature (12 nA/cm 2 at an internal electric field of 105 kV/cm), they operated as spectroscopic photon counting soft X-ray detectors uncooled at 30 °C. The measured energy resolution ( FWHM at 17.4 keV, Mo Kα) varied from 1.36 to 1.68 keV among different diodes. [ABSTRACT FROM AUTHOR]

A multipurpose facility for low cross section measurements has been developed at Inter University Accelerator Centre, New Delhi, India. The facility consists of a multipurpose miniature chamber equipped with 1 m focal length normal incidence Monochromator and charge coupled device based detection system which has been aligned to realize the best resolution of the spectrometer. The chamber in this facility collects radiation 100 times more efficiently from the older system, without using any extra focusing mirror assembly. It is ensured to have the provision of mounting an X-ray detector and the spectrometer transverse to the beam direction simultaneously in the same chamber. The atomic spectroscopic studies can be performed by interaction of ions beams with both thin foil and gas targets. Provision for using photomultiplier tube instead of charge coupled device, is employed in the system depending on the condition of the source strength or other detection issues. We observed the essence of a very weak atomic phenomenon, a triply excited autoionizing forbidden transition, using the above facility to demonstrate its capability for measuring such low cross section phenomena. The present developed facility covers a large spectroscopic region from X-rays to the near infrared (0.1–10,000 Å). [ABSTRACT FROM AUTHOR]

The ROOT based Offline and Online Analysis (ROAn) framework was developed to perform data analysis on data from Depleted P-channel Field Effect Transistor (DePFET) detectors, a type of active pixel sensors developed at the MPI Halbleiterlabor (HLL). ROAn is highly flexible and extensible, thanks to ROOT׳s features like run-time type information and reflection. ROAn provides an analysis program which allows to perform configurable step-by-step analysis on arbitrary data, an associated suite of algorithms focused on DePFET data analysis, and a viewer program for displaying and processing online or offline detector data streams. The analysis program encapsulates the applied algorithms in objects called steps which produce analysis results. The dependency between results and thus the order of calculation is resolved automatically by the program. To optimize algorithms for studying detector effects, analysis parameters are often changed. Such changes of input parameters are detected in subsequent analysis runs and only the necessary recalculations are triggered. This saves time and simultaneously keeps the results consistent. The viewer program offers a configurable Graphical User Interface (GUI) and process chain, which allows the user to adapt the program to different tasks such as offline viewing of file data, online monitoring of running detector systems, or performing online data analysis (histogramming, calibration, etc.). Because of its modular design, ROAn can be extended easily, e.g. be adapted to new detector types and analysis processes. [ABSTRACT FROM AUTHOR]

Spectroscopy focusing array (SFA) and polarimetry focusing array (PFA) are the two major payloads of the enhanced X-ray Timing and Polarimetry mission (eXTP). Nested Wolter-I X-ray mirror module is implemented in SFA and PFA to achieve a high effective area. When evaluating the properties of the mirror module, the alignment of the optical axis of the X-ray mirror module and a quasi-parallel X-ray beam is a prerequisite for ensuring accuracy of the results. To assist the alignment of the X-ray mirror module, an X-ray focal plane detector with one of the largest detection areas, is designed based on a back-illuminated scientific complementary metal–oxide–semiconductor transistor (sCMOS) sensor(GSENSE6060BSI; Gpixel Inc). Then the characteristics of readout noise, dark current, and split-pixel event properties of the detector are studied with the self-developed multi-target fluorescence X-ray source in a 100-m long X-ray test facility. The energy calibration is performed based on the single-pixel event, and the energy non-linearity of the detector is also observed. Finally, based on the optical model, the eXTP mirror module is simulated, and the alignment test of the Wolter-I X-ray mirror module designed for Einstein Probe/Follow-up X-ray Telescope via the "Burkert test" method is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Kaonic hydrogen atoms provide a unique laboratory to probe the kaon–nucleon strong interaction at the energy threshold, allowing an investigation of the interplay between spontaneous and explicit chiral symmetry breaking in low-energy QCD. The SIDDHARTA Collaboration has measured the K-series X rays of kaonic hydrogen atoms at the DAΦNE electron–positron collider of Laboratori Nazionali di Frascati, and has determined the most precise values of the strong-interaction induced shift and width of the 1s atomic energy level. This result provides vital constraints on the theoretical description of the low-energy interaction. [Copyright &y& Elsevier]

Abstract: A Monte Carlo model has been developed to predict the X-ray spectroscopic performance of silicon carbide detectors over the energy range 1–60keV. Consideration of the charge creation and diffusion in the different active layers along with provision for fluorescence and Compton scattering produce spectra that are in good agreement with measurements. Direct comparison of modelled spectra with X-ray data from a novel detector, the Semi-Transparent SiC Schottky Diode (STSSD) and comparison of SiC data from the literature also shows good agreement between the reported spectra and the model. Predicted quantum efficiencies are also presented. [Copyright &y& Elsevier]

Abstract: Al0.8Ga0.2As p+–p−–n+ diodes with low reverse leakage currents (<10nA) were evaluated as room temperature (23°C), soft X-ray photon-counting detectors. X-ray spectra from a 55Fe radioactive source show these diodes can be used for spectroscopy with promising energy resolution of 1.47keV FWHM at 5.9keV. At elevated reverse bias levels (>20V), we observed avalanche multiplication which, while improving the signal-to-noise ratio, degraded the spectroscopic performance. [Copyright &y& Elsevier]

Abstract: We describe a novel SiC Schottky diode architecture. The semi-transparent SiC Schottky diode has an “ultra-thin” (18nm Ni/Ti) Schottky contact, a gold annular overlayer and a gold corner-contact pad. We show that the new architecture exhibits the same essential characteristics as a more conventional “thick-contact” Schottky diode (⩾100nm). Such diodes will have a higher efficiency for low-energy (<5keV) X-rays than that of conventional structures combined with minimal self-fluorescence from the electrode materials. We present X-ray spectra from 55Fe, 109Cd and 241Am radioactive sources that show these diodes can be used for spectroscopy with promising energy resolution (1.47keV FWHM at 22keV) at room temperature (23°C). The reduction in contact thickness, however, does reduce the barrier height of the new diodes in comparison to those fabricated using the conventional process, and requires a trade-off between the low-energy detection threshold and the noise in the detector. [Copyright &y& Elsevier]

The precision of proton microprobe measurements of Sr in otoliths by proton induced X-ray emission (PIXE) has been improved significantly by use of a large area low resolution NaI(Tl) detector. This is achieved by scanning the sample simultaneously with a high resolution Si(Li) detector to measure the main constituent Ca and to confirm the absence of other elements in the counting window used by the large area detector. In our experimental setup the count rate for Sr was improved by a factor of 30. We took advantage of this to improve precision and achieve higher sample throughput in studies of diadromous fish, i.e. those whose life cycles may include both marine and freshwater stages. [Copyright &y& Elsevier]

Results from a silicon microstrip detector coupled to the RX64 ASIC are presented. The system is capable of single photon counting in digital X-ray imaging, with foreseen applications to dual energy mammography and angiography. The main features of the detecting system are low noise (operation with threshold as low as &ap;4 keV is possible), good spatial resolution (a pixel of 100 μm×300 μm when oriented edge-on) and good counting rate capability (up to one million counts per channel with a maximum rate of about 200 kHz per channel). The energy resolution of the system, as obtained with several fluorescence X-ray lines, is described. [Copyright &y& Elsevier]

Energy-dispersive detection of X-rays using silicon drift detectors has a wide range of applications, especially for non-destructive material analysis. As X-ray spectra are acquired by signal processing of detector output signals, a key element is a shaping filter used for determination of X-ray energy values within digital signal processing. A flattop region in this filter prevents degradation of spectra by ballistic deficit effects. Detectors with large active areas demand high flattop times due to slow maximum signal rise times, causing pile-up effects and loss of count rate capability. In this work an approach using an energy filter with variable flattop time is presented, adapting the flattop time on a pulse-to-pulse basis to signal rise time. Implementation in hardware and experimental investigation is done using a 150 mm2 active area silicon drift detector. Spectroscopic performance is investigated using a 55Fe source operating at 1 × 106 counts/s. Peaking times of 50 ns and 100 ns are considered. In two series of measurements, influence of ballistic deficit is investigated for static flattop times between 150 ns and 800 ns, and for adaptive flattop time with 150 ns to 450 ns additional flattop time. Full width at half maximum, position, symmetry, and area of Mn-K α peak are evaluated and compared. Results at similar influence of ballistic deficit show increased signal throughput for adaptive flattop time by 17 % using the 50 ns peaking time, and by 15 % using the 100 ns peaking time. Comparison at similar signal throughput, on the other hand, shows superior spectra quality achieved by adaptive flattop time, indicating a significantly lower impact of ballistic deficit. [ABSTRACT FROM AUTHOR]

We studied the X-ray spectroscopy capability and the detection efficiency of a low cost Commercial Off The Shelf CMOS Image Sensor (CIS) in the energy range from 6.4 to 24.9 keV using the fluorescence spectra emitted by FeNi, Cu, Zr, Pb, and Ag. The obtained results are compared with that obtained using a Silicon Drift Detector (SDD). We conclude that CIS is able to resolve fluorescence lines up to 17.7 keV but with a reduced detection efficiency. At lower energies, the energy resolution of the CIS is comparable to that obtained with the SDD. By the comparison of both detectors we also estimate the detection efficiency of the proposed method and the effective thickness of the CIS for all the measured X-ray lines. 00-01, 99-00. • The COTS CMOS image sensor (CIS) was able to resolve X-Ray lines up to 17.7 keV. • At lower energies, the energy resolution of the CIS and SDD are comparable. • The detection efficiency of CIS ranges from 5.5% at 6.4 keV to 0.12% at 17.7 keV. • The effective thickness of the CIS for all the measured X-ray lines was estimated. • COTS CMOS image sensors can be used to obtain multiespectral X-ray imaging. [ABSTRACT FROM AUTHOR]

Electronic structures of the temperature-induced valence transition system EuNi 2 (Si 1– x Ge x) 2 with x = 0.70, 0.79, 0.82 have been investigated by means of high-energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS). The HERFD-XAS spectra clearly change their intensities of Eu2+ and Eu3+ components which directly reflect the temperature-induced valence transition. For x = 0.70, gradual spectral change exhibits a continuous valence transition, while drastic changes for x = 0.79 and 0.82 indicate first-order valence transitions. High-energy resolution measurements made it possible to observe additional fine structures which are recognized more clearly below the transition temperature. Existence of these fine structures suggests that many-body effect plays an important role in the temperature-induced valence transition of this system. The variation of Eu mean valence estimated from the HERFD-XAS spectra for each x correlates with that of magnetic susceptibility. • Valence transition of EuNi 2 (Si 1- x Ge x) 2 proved by means of Eu L 3 HERFD-XAS. • Temperature-dependent fine structures reminiscent of change in many-body interaction through the valence transition. • Variation of Eu valence through the valence transition is associated with that of magnetic states. [ABSTRACT FROM AUTHOR]

Abstract: Pixel sensors have been calibrated using both fluorescence X-ray photons and an X-ray beam obtained by the transmission technique. The X-rays were generated by an Amptek EDIX 40 X-ray tube (maximum voltage 40kV). During the fluorescence calibration the pixel sensor was placed in front of the target in an off-beam position; the resulting photons hitting the detector were emitted by fluorescence in all directions with an energy which is typical of the fluorescence lines of the target material. During the calibration in the transmission mode the detector was placed behind the target, acting now as a filter, and the energy of the photons was tuned by adjusting the voltage of the tube and the thickness of the target. In this paper the comparison between the two methods will be shown. From the results of this test, it is possible to infer that transmission is more efficient (higher photon yield) and flexible (more energy points are possible) but produces broader spectral lines while fluorescence has a better energy definition. A reasonable strategy to benefit from both methods is using fluorescence to calibrate a spectrometer that will be used to evaluate the energy of the X-rays emitted in the transmission mode. The results of this calibration will be shown in this paper. [Copyright &y& Elsevier]

Abstract: Planetary exploration places high demands on instrumentation and presents some of the harshest operating environments and constraints known, including extreme thermal conditions, high-radiation tolerance and the need for low mass and power. We present data on a novel X-ray detector, the Semi-Transparent SiC Schottky Diode (STSSD), which shows promising energy resolution (1.3keV Full-Width Half-Maximum at 5.9keV) at room temperature and good radiation tolerance to proton irradiation (with a dose of ∼1013 cm−2, energy ∼50MeV) with some degradation in resolution to 2.5keV. Future development of SiC detectors will lead, in principle, to X-ray imaging spectroscopic arrays capable of meeting the stringent demands of future planetary exploration missions. We outline the detector requirements necessary for use in the environment likely to be encountered in a mission to the Jovian system, which has the harshest radiation environment of all the planetary magnetospheres. [Copyright &y& Elsevier]