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Cortez A.F.V.,University of Coimbra | Garcia A.N.C.,University of Coimbra | Neves P.N.B.,Institute Investigacao Interdisciplinar | Santos F.P.,University of Coimbra | And 4 more authors.
Journal of Instrumentation | Year: 2013

A recent experimental technique was used for measuring the mobility of positive ions originated from ethane in their parent gas. In this particular experiment, measurements were made in pure ethane (C2H6) for pressures ranging from 6 to 10 Torr and for reduced electric fields varying from 6 to 42 Td. The time of arrival spectra revealed two peaks and their reduced mobilities were determined. Extrapolation to zero field led to the values of 1.58 cm2V-1s-1 and 1.47 cm 2V-1s-1, which are likely to belong to a 3-carbon ions group which includes C3H5 +, C3H7 +, C3H8 + and C3H9 + and to a 4-carbon ions group which includes C4H9 + and C4H 10 + ions. For typical reduced electric fields used in gaseous detectors (E/N > 15 Td), the mobilities were 15% smaller than the Langevin limit [1]. © 2013 IOP Publishing Ltd and Sissa Medialab srl.


Cortez A.F.V.,University of Coimbra | Garcia A.N.C.,University of Coimbra | Neves P.N.B.,Institute Investigacao Interdisciplinar | Santos F.P.,University of Coimbra | And 4 more authors.
Journal of Instrumentation | Year: 2013

In this paper we present the experimental results for the mobility of ions in argon-ethane gaseous mixtures (Ar-C2H6) for pressures ranging from 6 to 10 Torr and for reduced electric fields in the 10 Td to 25 Td range, at room temperature. For Ar concentrations below 80% two peaks were observed in the time of arrival spectra which were attributed to ion species with 3-carbons (C3H7 +, C3H 8 + and C3H9 +) and with 4-carbons (which includes C4H7 +, C 4H9 +, C4H10 + and C4H12 + ions). For Ar concentrations above 80% a third peak appears, which may belong to C5H11 +. The time of arrival spectra for Ar concentrations of 80%, 85%, 90% and 95% are displayed in the present paper as well as the reduced mobilities determined from the peaks observed for a typical reduced electric field used in gaseous detectors (E/N = 15 Td).© 2013 IOP Publishing Ltd and Sissa Medialab srl.


Trindade A.M.F.,University of Coimbra | Cortez A.F.V.,University of Coimbra | Neves P.N.B.,Institute Investigacao Interdisciplinar | Garcia A.N.C.,University of Coimbra | And 6 more authors.
Journal of Instrumentation | Year: 2014

In this paper we present the results of the ion mobility measurements made in gaseous mixtures of argon (Ar) and methane (CH4) for pressures ranging from 5 to 8 Torr and for low reduced electric fields (in the 17 Td to 43 Td range), at room temperature. The time of arrival spectra of the several mixture ratios studied revealed that the relative abundance of the ions formed depend on the mixture ratios. For CH4 concentrations in the 2.5-10% range three well defined peaks were observed which were attributed to single-carbon ions (CH5 +), 2-carbon ions (C 2H4 + and C2H5 +), and 3-carbon ions (C3H4 +, C 3H5 +, C3H6 + and C3H7 +). The time of arrival spectra for CH4 concentrations of 2.5% (P-2.5), 5% (P-5), 10% (P-10) and the reduced mobilities of the ions obtained from the peaks observed are presented in this paper. The ion mobility study was performed for typical reduced electric fields used in gaseous detectors (E/N > 15 Td). © 2014 IOP Publishing Ltd and Sissa Medialab srl.


Garcia A.N.C.,University of Coimbra | Neves P.N.B.,Institute Investigacao Interdisciplinar | Trindade A.M.F.,University of Coimbra | Cortez A.F.V.,University of Coimbra | And 2 more authors.
Journal of Instrumentation | Year: 2014

In this paper we present the results for the ion mobility measurements made in gaseous mixtures of xenon (Xe) and nitrogen (N2) for low reduced electric fields (in the 15 Td to 30 Td range), at room temperature. The choice of reduced electric fields was guided by typical gaseous detector's demands. In the 0-100% range of Xe concentrations in the mixture, only one peak was observed which was attributed to Xe2+; in fact its mobility was found to follow Blanc's law. A typical time-of-arrival spectrum for 90% Xe and 10% N2 is shown. The reduced mobilities, obtained from the peaks, are calculated and presented in this paper. © 2014 IOP Publishing Ltd and Sissa Medialab srl.


Mendes R.V.,Institute Investigacao Interdisciplinar | Mendes R.V.,University of Lisbon
Chaos | Year: 2011

Using a cocycle formulation, old and new ergodic parameters beyond the Lyapunov exponent are rigorously characterized. Dynamical Renyi entropies and fluctuations of the local expansion rate are related by a generalization of the Pesin formula. How the ergodic parameters may be used to chracterize the complexity of dynamical systems is illustrated by some examples: clustering and synchronization, self-organized criticality and the topological structure of networks. © 2011 American Institute of Physics.

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