Pulse shape analysis of signals from BaF2 and CeF3 scintillators for neutron capture experiments

The scope of this work is to study the characteristics of BaF2 and CeF3 signals using fast digitizers, which allow the sampling of the signal at very high frequencies and the application of the fitting method for analysis of the recorded pulses. By this procedure particle identification and the reconstruction of pile-up events can be improved, while maintaining the energy and time-of-flight resolution as compared to traditional methods. The reliability of the technique and problems connected with data acquisition are discussed with respect to accurate measurements of neutron capture cross-sections

Infrared absorption analysis of organosilicon/oxygen plasmas in a microwave multipolar plasma excited by distributed electron cyclotron resonance

The dissociation of 4 groups of organosilicon monomers (such as hexamethydisiloxane, tetraethoxysilane, tetramethylsilane or tetramethoxysilane) in a MMP DECR reactor is analyzed by infrared absorption spectroscopy. The parent molecules are totally dissociated above 100 watts. The daughter stable molecules, such as C2H2, CH4, CO2, CO, C2H4 and OCH2 have been detected at low power but are dissociated at higher power. Each group exhibits its very own characteristics of dissociation as well as production of new species depending on its chemical composition. It seems that the DECR plasma at high energy dissociates the monomer molecule into its constituent atoms.La dissociation de 4 groupes de monomères organosiliciés (tels que l'hexaméthydisiloxane, le tétraéthoxysilane, le tétraméthylsilane ou encore le tétraméthoxysilane) dans un réacteur PMM RCER est analysée par spectroscopie d'absorption infrouge. Les molécules mères sont totalement dissociées au delà de 100 watts. Des molécules stables telles que C2H2, CH4, CO2, CO, C2H4 et OCH2 ont été détectées à faible puissance mais sont dissociées à plus forte énergie. Chaque groupe fait apparaitre ses propres charactéristiques au niveau de la dissociation ainsi que de la production de nouvelles espèces en fonction de sa composition chimique. Il semble que le plasma RCER dissocie les molécules en espèces atomiques

Neutron Capture Cross-Section Measurement of 151Sm at n_TOF.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Pulse Shape Analysis of Signals from BaF2 and CeF3 Scintillators for Neutron Capture Experiments

The scope of this work is to study the characteristics of BaF2 and CeF3 signals using fast digitizers, which allow the sampling of the signal at very high frequencies and the application of the fitting method for analysis of the recorded pulses. By this procedure particle identification and the reconstruction of pile-up events can be improved, while maintaining the energy and time-of-flight resolution as compared to traditional methods. The reliability of the technique and problems connected with data acquisition are discussed with respect to accurate measurements of neutron capture cross-sections.JRC.D.5-Neutron physic

A low-mass neutron flux monitor for the n_TOF facility at CERN

A small-mass system has been developed for monitoring the flux of neutrons with energy up to 1 MeV at the new time-of-flight facility at CERN, n_TOF. The monitor is based on a thin Mylar foil with a Li-6 deposit, placed in the neutron beam, and an array of Silicon detectors, placed outside the beam, for detecting the products of the Li-6(n, alpha)H-3 reaction. The small amount of material on the beam ensures a minimal perturbation of the flux and minimizes the background related to scattered neutrons. Moreover, a further reduction of the gamma-ray background has been obtained by constructing the scattering chamber hosting the device in carbon fibre. A detailed description of the flux monitor is here presented, together with the characteristics of the device, in terms of efficiency, resolution and induced background. The use of the monitor in the measurement of neutron capture cross-sections at n_TOF is discussed.Peer reviewe

New experimental validation of the pulse height weighting technique for capture cross-section measurements

The accuracy of the pulse height weighting technique for the determination of neutron capture cross-sections is investigated. The technique is applied to measurements performed with C6D6 liquid scintillation detectors of two different types using capture samples of various dimensions. The data for well-known (n,γ) resonances are analyzed using weighting functions obtained from Monte Carlo simulations of the experimental set-up. Several causes of systematic deviation are identified and their effect is quantified. In all the cases measured the reaction yield agrees with the standard value within 2%. © 2003 Elsevier B.V. All rights reserved

Time-energy relation of the n_TOF neutron beam: Energy standards revisited

The accurate determination of neutron cross-sections as a function of the neutron energy at a time-of-flight facility requires a precise knowledge of the time-energy relation for the neutron beam. For the n_TOF neutron beam at CERN, produced by spallation of high-energy protons on a Pb target, the time-energy relation is connected to the production mechanism and to the subsequent moderation process. A calibration of the neutron energy scale is proposed based on detailed Monte Carlo simulations of the facility. This time-energy relation has been experimentally validated by means of dedicated measurements of standard energy resonances, from 1eV to approximately 1MeV. On the basis of the present measurements, it is proposed to correct the energy of the 1.3eV resonance of 193Ir, which is commonly considered as an energy standard. © 2004 Elsevier B.V. All rights reserved

A low-mass neutron flux monitor for the n_TOF facility at CERN

A small-mass system has been developed for monitoring the flux of neutrons with energy up to 1 MeV at the new time-of-flight facility at CERN, n_TOF. The monitor is based on a thin Mylar foil with a 6Li deposit, placed in the neutron beam, and an array of Silicon detectors, placed outside the beam, for detecting the products of the 6Li(n, α)3H reaction. The small amount of material on the beam ensures a minimal perturbation of the flux and minimizes the background related to scattered neutrons. Moreover, a further reduction of the γ-ray background has been obtained by constructing the scattering chamber hosting the device in carbon fibre. A detailed description of the flux monitor is here presented, together with the characteristics of the device, in terms of efficiency, resolution and induced background. The use of the monitor in the measurement of neutron capture cross-sections at n-TOF is discussed