Full Geant4 and FLUKA Simulations of an e-LINAC for its Use in Particle Detectors Performance Tests

In this work we present the results of full Geant4 and FLUKA simulations and comparison with dosimetry data of an electron LINAC of St. Maria Hospital located in Terni, Italy. The facility is being used primarily for radiotherapy and the goal of present study is the detailed investigation of electron beam parameters to evaluate the possibility to use the e-LINAC (during time slots when it is not used for radiotherapy) to test the performance of detector systems in particular those designed to operate in space. The critical beam parameters are electron energy, profile and flux available at the surface of device to be tested. The present work aims to extract these parameters from dosimetry calibration data available at the e-LINAC. The electron energy ranges is from 4 MeV to 20 MeV. The dose measurements have been performed by using an Advanced Markus Chamber which has a small sensitive volume.Comment: 10 pages, 10 figures, 2 table

The chemical and electrochemical oxidative polymerization of 2-amino-4-tert-butylphenol

[EN] Poly(2-amino-4-tert-butylphenol), poly(2A-4TBP), was synthesized from monomer aqueous solution using either electrochemical or chemical oxidation procedures. Several spectroscopic characterization techniques were employed to gain information on the chemical structure and redox behavior of the obtained materials. It was found that the chemical polymerization product could be described as an oligomer mixture containing up to 16 monomer units. In parallel to other polymers derived from o-aminophenol, phenoxazine rings constitute also the basic structure of poly(2A-4TBP). In addition, the occurrence of N-N couplings, which are favored by the presence of the voluminous tert-butyl substituent, seems also relevant. No significant structural differences were found between the chemically or electrochemically synthesized materials. © 2016 Published by Elsevier Ltd.Financial support from the Spanish Ministerio de Economía y Competitividad and FEDER funds (MAT2013-42007-P) and from the Generalitat Valenciana (PROMETEO2013/038) is gratefully acknowledged. M. Abidi thanks the Ministry of Higher Education and Scientific Research of Tunisia for funding her stay at the University of Alicante.Abidi, M.; López-Bernabeu, S.; Huerta, F.; Montilla-Jiménez, F.; Besbes-Hentati, S.; Morallón, E. (2016). The chemical and electrochemical oxidative polymerization of 2-amino-4-tert-butylphenol. Electrochimica Acta. 212:958-965. https://doi.org/10.1016/j.electacta.2016.07.060S95896521

Optical transmission spectroscopy of switchable yttrium hydride films.

The optical transmission of the recently discovered switchable yttrium hydride films is determined spectroscopically as a function of hydrogen content. This is done during electrochemical loading of Pd-capped Y film electrodes, thereby continuously changing the hydrogen concentration. The effect of the Pd cap layer on the film transmission is determined from measurements on a series of films with varying Pd layer thickness. The results are in good agreement with transmission measurements of in situ gas phase loaded, uncapped Y films. Both data sets can be consistently described with simple optical decay lengths such as 277.8 nm for YH3−δ and 15.1 nm for Pd at ħω=1.96 eV. The hydrogen concentration dependence of the optical transmission is discussed and compared with previous optical measurements on bulk samples and band-structure calculations

EQCM and XPS investigations on the redox switching of conducting poly(o-aminophenol) films electrosynthesized onto Pt substrates

The redox behaviour of conducting poly(o-aminophenol) films (PoAP), potentiodynamically electrosynthesized onto Pt substrates, was studied by means of in situ Electrochemical Quartz Crystal Microbalance (EQCM), varying the composition, concentration and pH of the acidic supporting electrolyte. PoAP films at different oxidation stages were also characterized by ex situ X-ray Photoelectron Spectroscopy (XPS), stopping the anodic scan at +0.1 V (semi-oxidized PoAP) and +0.5 V vs Ag/AgCl (oxidized PoAP). The results were interpreted by comparison with previous investigations carried out on the reduced PoAP. Polymer oxidation proceeds through the deprotonation of aminic site susceptible then to oxidation. The incorporation of perchlorate ions occurs mostly at the beginning of the anodic scan till the peak potential is reached. At this stage of the oxidation positively charged nitrogens, polaron type, are present which then recombine each other to give bipolaron and, upon deprotonation, neutral immines. The overall PoAP redox oxidation is a reversible two electrons process complicated by chemical deprotonation steps before and after the oxidation itself. On the reverse scan immines require protonation in order to be reduced. A diffusional type limitation on the cathodic process was demonstrated and attributed to counter ions diffusion through the polymer accompanying its protonation. The XPS investigation allowed to unambiguously prove the presence of water inside the film, already suggested by the authors for the reduced PoAP by heating experiments in ultra-high vacuum conditions. Rinsing the polymer with acetonitrile before the XPS analysis, the relevant detailed C1s, N1s and O1s regions evidenced the presence of ammonium acetate coming from nitrile hydrolysis. A higher amount of water was evidenced in the oxidized states with respect to the reduced form. The exchanged molar mass calculated by EQCM revealed, indeed, solvent entrance in the last part of the oxidation. Accordingly, the Binding Energies characteristic of neutral nitrogen functionalities suggested that polymer chains are more distant in the oxidized state, preventing the incoming of hydrogen bonds

Full Geant4 and FLUKA simulations of an e-LINAC for its use in particle detectors performance tests

In this work we present the results of full Geant4 and FLUKA simulations and comparison with dosimetry data of an electron LINAC of St. Maria Hospital located in Terni, Italy. The facility is being used primarily for radiotherapy and the goal of present study is the detailed investigation of electron beam parameters to evaluate the possibility to use e-LINAC (during time slots when it is not used for radiotherapy) to test the performance of detector systems in particular those designed to operate in space. The critical beam parameters are electron energy, profile and flux available at the surface of device to be tested. The present work aims to extract these parameters from dosimetry calibration data available at e-LINAC. The electron energy range is from 4 MeV to 20 MeV. The dose measurements have been performed by using an Advanced Markus Chamber which has a small sensitive volume

Reaction of Hydroxyl Radicals with C4H5N (Pyrrole): Temperature and Pressure Dependent Rate Coefficients

Absolute (pulsed laser photolysis, 4−639 Torr N2 or air, 240−357 K) and relative rate methods (50 and 760 Torr air, 296 K) were used to measure rate coefficients k1 for the title reaction, OH +C4H5N → products (R1). Although the pressure and temperature dependent rate coefficient is adequately represented by a falloff parametrization, calculations of the potential energy surface indicate a complex reaction system with multiple reaction paths (addition only) in the falloff regime. At 298 K and 760 Torr (1 Torr = 1.33 mbar) the rate coefficient obtained from the parametrization is k1 = (1.28 ± 0.1) × 10−10 cm3 molecule−1 s−1, in good agreement with the value of (1.10 ± 0.27) × 10−10 cm3 molecule−1 s−1 obtained in the relative rate study (relative to C5H8, isoprene) at this temperature and pressure. The accuracy of the absolute rate coefficient determination was enhanced by online optical absorption measurements of the C4H5N concentration at 184.95 nm using a value σ184.95nm = (1.26 ± 0.02) × 10−17 cm2 molecule−1, which was determined in this work.Fil: Dillon, Terry J.. Max-Planck-Institut für Chemie; AlemaniaFil: Tucceri, Maria Eugenia. Max-Planck-Institut für Chemie; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Dulitz, Katrin. Max-Planck-Institut für Chemie; AlemaniaFil: Horowitz, Abraham. Max-Planck-Institut für Chemie; AlemaniaFil: Vereecken, Luc. Max-Planck-Institut für Chemie; AlemaniaFil: Crowley, John N.. Max-Planck-Institut für Chemie; Argentin