Papers by Keyword: X-Ray Spectroscopy

Abstract: Magnetized plasmas in compact traps offer a unique environment for fundamental research. PANDORA (Plasma for Astrophysics Nuclear Decay Observations and Radiation for Archeometry) is a multidisciplinary project focused on studying β decays in plasmas, using a novel facility that replicates stellar-like conditions. The project also supports applications to materials science, accelerator and ion source technologies, etc. A plasma diagnostics system based on a soft X-ray pinhole camera has been designed and implemented, with an innovative algorithm for Single-Photon Counting (SPhC) and High Dynamical Range (HDR) analysis. This enables space-resolved X-ray spectroscopy and the determination of magneto-plasma properties like local thermodynamic parameters (in terms of electron density and temperature) and confinement dynamics. This work presents results from an AI-based model in MATLAB designed to optimize the above mentioned algorithm. Using K-means clustering, events with similar features were grouped to identify those distinguishing real from spurious ones. A labeled dataset then is used to train a neural network to minimize pile-up, accelerating the recovery of high-resolution spectra and improving soft X-ray emission analysis. This contribution details the current neural network development stage and first applications to experimental data acquired during an experimental campaign carried out at the ATOMKI Laboratory.

Abstract: We study stable stable transparent monolithic nanocomposites based on the silica matrix doped with CdS nanoparticles (NPs) of different nature. The first kind of nanocomposite was obtained by nucleation and growth of nanoparticles in glass matrix during heat treatment. The second nanocomposite was obtained by immobilization of pre-made nanoparticles into silica gel matrix. This work is focused on characterization of the nanocomposites in the submicron scale by using electron microscopy and small angle x-ray scattering techniques. Experimental results show that both types of nanocomposites have homogeneous distribution of quantum dots. Form-factor and average size of CdS NPs depend on the synthesis technique

Abstract: The design and the experimental results of some prototypes of SiC X-ray detectors are presented. The devices have been manufactured on a 2’’ 4H-SiC wafer with 115 m thick undoped high purity epitaxial layer, which constitutes the detection’s active volume. Pad and pixel detectors based on Ni-Schottky junctions have been tested. The residual doping of the epi-layer was found to be extremely low, 3.7 x 1013 cm-3, allowing to achieve the highest detection efficiency and the lower specific capacitance of the detectors. At +22°C and in operating bias condition, the reverse current densities of the detector’s Schottky junctions have been measured to be between J=0.3 pA/cm2 and J=4 pA/cm2; these values are more than two orders of magnitude lower than those of state of the art silicon detectors. With such low leakage currents, the equivalent electronic noise of SiC pixel detectors is as low as 0.5 electrons r.m.s at room temperature, which represents a new state of the art in the scenario of semiconductor radiation detectors.

Abstract: The paper deals with the effect of cooling rate on solidification behavior of IN 738LC nickel based superalloy and on resulting structural and chemical microheterogeneity of this alloy. Samples taken from as-received state were heated with controlled ramp rates (1, 5, 10 and 20 °C min-1). Immediately after melting they were cooled with the same controlled ramp rate with the help of the laboratory experimental system SETARAM SETSYS 18TM TG/DTA/TMA. Then the microanalysis of minority phases was conducted with use of X-ray spectroscopy and microstructure of the individual samples was documented by scanning electron microscopy. Chemical microheterogeneity was determined on the basis of measured concentration data of selected elements (Al, Ti, Cr, Co, Ni, Nb, Mo, Ta and W) in representative areas of the individual samples structure.

Abstract: To investigate doping-free zirconia, pulsed laser ablation technique was applied to synthesize pure zirconia nanoparticles. Various experimental parameters were investigated by means of microscopic, spectroscopic and diffractmetric techniques to reveal morphology and production yield. It is successful to form cubic and monoclinic phases at nanometer-scale fine particles. The cubic phase has relatively small lattice parameters than the stabilized zirconia.

Abstract: High performance SiC detectors for ionising radiation have been designed, manufactured and tested. Schottky junctions on low-doped epitaxial 4H-SiC with leakage current densities of few pA/cm2 at room temperature has been realised at this purpose. The epitaxial layer has been characterised at different dose of radiations in order to investigate the SiC radiation hardness. The response of the detectors to alpha and beta particle and to soft X-ray have been measured. High energy resolution and full charge collection efficiency have been successfully demonstrated.

Abstract: Currently, many semiconductor compounds, particularly Cd1-xZnxTe, have attracted attention for applications in detection of radiation, due to the very good resolution without cryogenic cooling (a 1.3 keV-FWHM at the 122 keV line from 57Co is reported for some detectors). In this study the properties of a zinc doped cadmium telluride detector mounted on a thermoelectric cooler (Amptek Inc., model XR-100T-CZT) were studied. The detection system is based on a Cd0.9Zn0.1Te crystal of 3x3x2 mm, which operates at approximately -21°C and uses a rise time discrimination (RTD) circuit to improve the energy resolution. Although the quantum efficiency of this compound is very high, the small dimensions of the crystal limit its use to low energy photons (some hundreds of keV). Because of the carrier trapping characteristics of CZT, the experimental determination of the response function is essential. In this work it was measured in the range of energies from 10 to 400 keV, employing gamma rays and fluorescence x-rays from different sources (57Co, 133Ba, 152Eu and 241Am). In spite of the experimental difficulties, the x-ray escape fraction was also evaluated, making it possible the correction of the distortion it causes in the measured spectra. Measurements of x-ray spectra produced by a tungsten tube operating at small currents were carried out, and the stripping procedure was performed, taking into account the two contributions (efficiency and escape fraction). Results obtained point to the feasibility of use of this detector for in-situ diagnostic x-ray spectroscopy, provided that low intensity beams are available.