arXiv subjects

E. Collet

Publications and source records attributed to E. Collet.

7 recordsLinked to original sources

arXiv2025

Development & first Performance evaluation of multi-element monolithic HPGe detector for X-ray spectroscopy

The first operational prototype of a high-purity Germanium (HPGe) detector developed within the European LEAPS-INNOV project is presented in this work. This prototype features a monolithic, multi-element sensor optimized for high-resolution X-ray spectroscopy in the hard X-ray regime, capable of handling high count rates (20-250 kcps/mm2) across a broad energy range (5-100 keV). We discuss here a complete laboratory-based characterization of the detector's performance, as well as an on-beam evaluation at the BM05 beamline of the ESRF synchrotron facility, using monochromatic X-rays in the 20-50 keV energy range. We provide a detailed performance assessment that also includes a phenomenological defect-depth estimation model.

physics.ins-det↗

arXiv2025

Next Generation Multi-element monolithic Germanium detectors for Spectroscopy: First integration at ESRF facility

The XAFS-DET work package of the European LEAPS-INNOV project is developing a high-purity Germanium detectors for synchrotron applications requiring spectroscopic-grade response. The detectors integrate three key features: (1) newly designed monolithic Germanium sensors optimised to mitigate charge-sharing events, (2) an improved cooling and mechanical design structure supported by thermal simulations, and (3) complete electronic chain featuring a low-noise CMOS technology-based preamplifier. enabling high X-ray count rate capability over a broad energy range (5-100 keV). This paper discusses the first integration and characterization of one of the two multi-element Ge detectors at the European Synchrotron Radiation Facility (ESRF). The integration phase included validating high-throughput front-End electronics, integrating them with the Ge sensor, and operating them at liquid nitrogen temperature, in addition to the experimental characterization, which consists of electronics noise study and spectroscopic performance evaluation.

physics.ins-det↗

arXiv2025

Progress in the Development of Multi-Element Monolithic Germanium Detectors in LEAPS-INNOV Project: Insights from Detector Performance Simulation

This study presents a detailed simulation-based analysis of the detection limits of multi-element monolithic Germanium (Ge) detectors to cadmium traces in environmental soil samples. Using the capabilities of the Geant4 Monte Carlo toolkit in combination with the Solid State Detector Package, we evaluated the detection limit variation with the sample-to-detector distances and photon flux. These simulations were conducted to mimic realistic conditions, with a photon flux measured by the SAMBA beamline at the SOLEIL synchrotron facility. Our findings for the detection limit for trace amounts of pollutants in low concentrations like cadmium in the soil provide valuable insights for optimizing experimental setups in environmental monitoring and synchrotron-based applications, where precise detection of trace elements is critical.

physics.ins-det↗

arXiv2020

Strain Wave Pathway to Semiconductor-to-Metal Transition revealed by time resolved X-ray powder diffraction

Thanks to the remarkable developments of ultrafast science, one of today's challenges is to modify material state by controlling with a light pulse the coherent motions that connect two different phases. Here we show how strain waves, launched by electronic and structural precursor phenomena, determine a macroscopic transformation pathway for the semiconducting-to-metal transition with large volume change in bistable Ti$_3$O$_5$ nanocrystals. Femtosecond powder X-ray diffraction allowed us to quantify the structural deformations associated with the photoinduced phase transition on relevant time scales. We monitored the early intra-cell distortions around absorbing metal dimers, but also long range crystalline deformations dynamically governed by acoustic waves launched at the laser-exposed Ti$_3$O$_5$ surface. We rationalize these observations with a simplified elastic model, demonstrating that a macroscopic transformation occurs concomitantly with the propagating acoustic wavefront on the picosecond timescale, several decades earlier than the subsequent thermal processes governed by heat diffusion.

cond-mat.mtrl-sci↗

arXiv2016

Ultrafast non-thermal laser excitation of gigahertz longitudinal and shear acoustic waves in spin-crossover molecular crystals [$Fe(PM-AzA)_{2}$$(NCS)_{2}$]

We report GHz longitudinal as well as shear acoustic phonons photoexcitation and photodetection using femtosecond laser pulses in a spin-crossover molecular crystal. From our experimental observation of time domain Brillouin scattering triggered by the photoexcitation of acoustic waves across the low-spin (LS) to high-spin (HS) thermal crossover, we reveal a link between molecular spin state and photoexcitation of coherent GHz acoustic phonons. In particular, we experimentally evidence an unconventional non-thermal pathway for the laser excitation of GHz phonons. We also provide experimental insight on the optical and mechanical parameters evolution across the LS/HS spin crossover temperature T$_{1/2}$.

cond-mat.mtrl-sci↗

arXiv2011

Ultrafast Spectral Weight Transfer in RBaCo2O6-delta (R=Sm, Gd, and Tb): A Role of Electronic Correlation in Photoinduced Phase Transition

We performed femtosecond reflection spectroscopy on a series of perovskite-type cobalt oxide $R$BaCo$_2$O$_{6-\delta}$ ($R$=Sm, Gd, and Tb) crystals, in which the electronic transfer was controlled by $R$. The transient reflectivity and the optical conductivity ($\sigma^{\rm PI}(\omega)$) obtained by Kramers-Kronig analysis showed an ultrafast change within a time resolution ($\approx 150$ fs) at room temperature and the appearance of signals of a hidden state different from the high temperature metallic state. The transferred spectral weight in $\sigma^{\rm PI}(\omega)$ upon photoexcitation sensitively depended on the $R$-species, indicating an important role of electronic correlation in the photoexcited state.

cond-mat.str-el↗

arXiv2010

Ferromagnetically coupled Shastry-Sutherland quantum spin singlets in (CuCl)LaNb$_2$O$_7$

Using inelastic neutron scattering, x-ray, neutron diffraction, and the first-principle calculation techniques, we show that the crystal structure of the two-dimensional quantum spin system (CuCl)LaNb$_2$O$_7$ is orthorhombic with $Pbam$ symmetry in which CuCl$_4$O$_2$ octahedra are tilted from their high symmetry positions and the Cu$^{2+} (s = 1/2)$ ions form a distorted square lattice. The dominant magnetic interactions are the fourth nearest neighbor antiferromagnetic interactions with a Cu-Cl--Cl-Cu exchange path, which lead to the formation of spin singlets. The two strongest interactions between the singlets are ferromagnetic, which makes (CuCl)LaNb$_2$O$_7$ the first system of ferromagnetically coupled Shastry-Sutherland quantum spin singlets.

cond-mat.str-el↗