DUVEX: An X-ray counting system based on YAG:Ce scintillator

International audienceA detector system, called DUVEX, has been developed for the soft-X-ray and extreme ultraviolet domain. It consists of a YAG:Ce scintillator coupled to a photomultiplier module working under vacuum in counting mode. The design and the performances of this detector in terms of yield, absolute efficiency, response and noise are reported. Spectra in the soft X-ray range of different elements (W, Ag, Al, Mg, Cu, N, C and B) obtained in WDS mode using this detector are presented. DUVEX appears as a competitive detection tool in terms of cost and easiness of implementation

Experimental determination of X-ray atomic fundamental parameters of nickel

Abstract X-ray atomic properties of Nickel were investigated in a singular approach that combines different experimental techniques to obtain new and useful reliable values of atomic fundamental parameters for X-ray spectrometric purposes and for comparison to theoretical predictions. We determined the mass attenuation coefficients in an energy range covering the L- and K- absorption edges, the K-shell fluorescence yield and the Kb/Ka and Kb1,3/Ka1,2 transition probability ratios. The obtained line profiles and linewidths of the Ka and Kb transitions in Ni can be considered as the contribution of the satellite lines arising from the [KM] shake processes suggested by Deutsch et al. [1] and Ito et al. [2]. Comparison of the new data with several databases showed a good agreement but also discrepancies were found with existing tabulated values

Motifs transverses et solitons de cavité dans des microrésonateurs à semiconducteurs pompés optiquement

The work presented in this memory relates to the study of Transverse Optics phenomena and cavity solitons in III-V semiconductor microresonators. Those result from the interaction of an external beam injected into the cavity with the non-linearities of the active material and diffraction. The originality of this work is due to the optical pumping of the vertical cavity semiconductor optical amplifier (VCSOA). First of all, we develop the theoretical aspects of physics brought into play, then the practical and technological aspects concerning the design and the realization of VCSOAs presenting characteristics favorable to the emergence of phenomena of transverse optics. Most of work, either theoretical or technological, relates to the management of the residual heating and the attenuation of its inhibiting effects of the observation of cavity solitons. The experiments presented here show for the first time the formation of transverse patterns and the possibility of writing and erasing in either a coherent and anincoherent way cavity solitons under optical pump regime.Le travail présenté dans ce mémoire concerne l'étude dans les microrésonateurs à semiconducteur III-V des phénomènes d'Optique Transverse que sont les solitons de cavité. Ceux-ci résultent de l'interaction d'un faisceauexterne injecté dans la cavité avec les non-linéarités du matériau actif et la diffraction. L'originalité de ce travail tient au pompage optique de l'amplificateur semiconducteur à cavité verticale (VCSOA). On s'est d'abord attaché à développer les aspects théoriques de la physique mise en jeu, puis les aspects pratiques et technologiques concernant la conception et la réalisation des VCSOAs présentant des caractéristiques favorables à l'émergence de phénomènes d'optique transverse. Une grande partie du travail, que ce soit théorique outechnologique, concerne la maitrîse du chauffage résiduel et l'atténuation de ses effets inhibiteurs de l'observation des solitons de cavité. Les expériences présentées ici montrent pour la première fois la formation de motifs transverses et la possibilité d'écrire et d'effacer de manière cohérente et incohérente des solitons de cavité en régime de pompage optique

Combined x-ray reflectivity and grazing incidence x-ray fluorescence analysis of a Ta/Cr/Pt trilayer stack

International audienceMeasurements of X-ray reflectivity (XRR) and Grazing incidence x-ray fluorescence (GIXRF) were performed at the Métrologie beamline of SOLEIL synchrotron with the CASTOR setup with 6.25 keV incident photons

Primary calibration of photodiodes with monochromatic X‐ray beams using an electrical‐substitution radiometer

International audienceThe electrical-substitution cryogenic detector BOLometer for Use in the range of X-rays (BOLUX), which was developed some years ago at CEA/DAM, has been set up and restarted now at LNHB. It has been used for the primary measurement of the intensity (total energy per unit time) of monochromatic synchrotron beams in the energy range from 3 to 30 keV. These well-determined photon beams have been employed for the efficiency calibration of two photodiodes in terms of current induced per unit optical power at different photon energies. In a final step, we explored the possibility to use these primary calibrated photodiodes to determine the efficiency curve of an energy dispersive spectrometer based on a semiconductor detector (Silicon Drift Detector) using less intense monochromatic photon fluxes. The characteristics of the radiometer BOLUX and its principle of operation are described, and the measurements carried out at the synchrotron beamline are presented, including the determination of the beams' intensities, the direct calibration of photodiodes with respect to BOLUX and the use of one of those photodiodes as a standard transfer for the calibration of the SDD

Absolute calibration of photodiodes with a monochromatic beam measured with an electrical-substitution radiometer

International audienceTraditional efficiency calibration of spectrometers is based on the measurement of sources of radionuclides calibrated in activity and whose emission probabilities are known beforehand. However, there are regions of the spectrum where there is a lack of reliable tabulated emission probabilities. Furthermore, if one aims to improve the measurement of emission probabilities, this approach implies the use of the same parameters that one intends to measure. The solution to these limitations is the use of photon fluxes whose intensity has been measured in an absolute way by another technique. Photodiodes constitute a very suitable choice for measuring the intensity of these fluxes, but they need to be previously calibrated in terms of amount of current generated per unit power. In this work, we present the calibration of several photodiodes with a monochromatic photon beam whose intensity is previously measured in an absolute way by a cryogenic electrical-substitution radiometer.Cryogenic detectors are based on the measurement of the temperature rise experienced by an absorber when the radiation interacts with it. In electrical-substitution radiometers, the amount of incident energy is determined by finding the electrical power that must be dissipated in the material to get the same temperature rise obtained during the photonic heating. In order to monitor temperature, a thermistor is polarized by a constant current, so the diminution of resistance induced by the temperature rise implies a decrease of its potential.In this work, the intensity of monochromatic beams is measured by means of the radiometer BOLUX (BOLometer for Use in the field of X-rays). This measurement is corrected by transmission, escape and scattering in BOLUX's absorber. Afterwards the current generated in the photodiode is measured when the same beam impinges on it, in order to obtain its efficiency at that photon energy. Measurements were performed at two different beamlines (Métrologie and PUMA) at synchrotron SOLEIL, covering an energy range from 3 keV to 60 keV. Absolute calibration of photodiodes also plays an important role in all those applications that rely on well-characterized photon fluxes, such as reference-free X-ray spectrometry

Estimating the uncertainties in combined GIXRF-XRR for the characterization of innovative materials

International audienceThe combination of XRR and GIXRF is used for the characterization of thin films and multilayered materials, since both techniques use similar measuring and data analysis procedures. Since XRR is more sensitive to the electronic density, it is used to determine the thickness and roughness of thin layers, and GIXRF, being more sensitive to the elemental density, provides information on the depth distribution of the elements. Therefore, combining these two techniques leads to more accurate characterization than with a single technique [1]. However, there is a major difficulty to determine the associated uncertainties, due to the large number of parameters and more specifically, to the combination of the two methods with dramatically different dynamic ranges.The objective in this work is to quantify the uncertainties on the parameters of the optimized structure (thicknesses, roughness, density, etc.). Since repeating the combined measurements is a time-consuming process, we propose a recursive method for the estimation of the uncertainties of the data from the GIXRF-XRR analysis, based on the Bootstrap statistical method [2]. This method allows the generation of random uniform weights, between 0 and 1, that are multiplied by the absolute difference between the experimental and theoretical values. The application of these weights results in new sets of calculated values and the uncertainties on the optimized parameters can be derived.This method was applied to combined GIXRF-XRR measurements which where carried out in the goniometer CASTOR (Chamber of Spectrometric Analysis in Transmission or in Reflection) at the hard X-ray Metrology beamline of the synchrotron SOLEIL facility [3]. One of the studied samples is an amorphous chalcogenide GeSbTe (germanium, antimony and tellurium) thin film. In order to excite the Kα-line of germanium and the Lα-lines of tellurium and antimony, the GIXRF data were acquired at an excitation energy of 11.5 keV, while the XRR measurements were carried out at an excitation energy of 8 keV, in order to benefit from the highest photon flux.First, XRR data were analyzed with IMD [4] to obtain an estimation of the structural composition and then GIXRF spectra were fitted with COLEGRAM [5] to derive the intensity of the fluorescence X-ray lines. Finally, starting with the model obtained with IMD and the fitted fluorescence data, the GIXRF-XRR analysis was performed using in-house software to derive the sample structure and associated uncertainties

Radionuclide-free efficiency calibration of an HPGe detector using monochromatic photon beams measured with a cryogenic radiometer

International audienceThe efficiency calibration of spectrometers is traditionally based on the measurement of radioactive sources calibrated in activity and whose emission intensities are known. However, in the energy range below 60 keV, there is a lack of reliable tabulated emission intensities and some inconsistencies have been highlighted. Furthermore, if one aims to improve the measurement of emission probabilities, this approach implies the use of the same parameters that one intends to measure. The solution to these limitations is the use of photon fluxes whose intensity has been determined in an absolute way by another technique. Here we present the calibration of a high-purity germanium (HPGe) detector in the energy range from 3 keV to 60 keV through a procedure that involves the following sequence of steps:First, the intensity of a monochromatic photon beam was measured by means of a cryogenic electrical-substitution radiometer BOLUX (BOLometer for Use in the field of X-rays) . Cryogenic detectors are based on the measurement of the temperature rise experienced by an absorber when the radiation interacts with it. In particular, in electrical-substitution radiometers, the amount of incident energy is determined by finding the electrical power that must be dissipated in the material to get the same temperature increase than that obtained during the photonic heating. Second, these well-determined photon beams have been employed for the calibration of different photodiodes in terms of current induced per unit optical power (efficiency) at different photon energies. Finally, for each energy step, the efficiency calibration of an energy-dispersive spectrometer based on an HPGe detector was obtained by comparison with the primarily-calibrated photodiodes.The calibration measurements were performed at two different beamlines (Métrologie and PUMA) of the SOLEIL synchrotron facility, and different photodiodes were used to cover the energy range of interest. The experimental approach and efficiency results will be detailed.The final application of this study is the use of the radionuclide-free calibrated spectrometer to determine new values of absolute X-ray emission intensities for radionuclides, starting with 109Cd and 152Eu.[1] Applied Radiation and Isotopes, Volume 134, April 2018, Pages 131-136 [2] Presented at EXRS2022, submitted to X-Ray Spectrometr

Combien de photons ?

International audienceLa connaissance du flux de photons X incidents est nécessaire pour les analyses quantitatives. C’est aussi une donnée primordiale quand on souhaite connaître la dose reçue par un échantillon biologique. Le LNE-LNHB, laboratoire primaire français pour la métrologie des rayonnements ionisants, a parmi ses missions celle d’étalonner sources et détecteurs. Le LNE-LNHB étalonne en rendement des détecteurs (photodiodes, SDD) pour ses propres besoins d’analyses quantitatives et sans référence (analyse combinée XRR-GIXRF). Le LNE-LNHB a repris l’activité bolomètre du CEA-DAM en 2020. Ce bolomètre (BOLUX) permet de mesurer la puissance optique reçue