Percorrer por autor "Neves, P.N.B."
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- Drift field limitations to the energy resolution in Time Projection Chambers for 136Xe neutrino-less double beta decay searchPublication . Neves, P.N.B.; Conde, C.A.N.; de Oliveira Pegado de Noronha E Távora, Luís MiguelThe effect of drift electric field in the degradation of the energy resolution of gaseous xenon Time Projection Chambers for the search of neutrino-less double beta decay of 136Xe is calculated with the PENELOPE code. Calculations are presented first for single electron emission with energies from 0.2 to 3 MeV and reduced electric fields in the 0.1–2 V cm−1 Torr−1 range, showing energy resolution degradations by as much as 12% (FWHM). Calculations are also presented for neutrino-less double beta decay of 136Xe assuming two decay mechanisms, the mass mechanism (MM) and the right-handed current due to the λ parameter (RHCλ) mechanism, for reduced drift electric fields in the 0.03–0.8 V cm−1 Torr−1 range. It is shown that the drift field degrades the energy resolution of the two electrons sum peak (2457.8 keV) by an amount that is significant even for reduced fields as low as 0.1 V cm−1 Torr−1. It is concluded that to reach the experimental target of 1% (FWHM) for the energy resolution of TPCs set-ups (like the NEXT collaboration set-up) the drift electric field should be weaker than about 0.1 V cm−1 Torr−1.
- Experimental measurement of H3+/H5 + and D3+/D5+ mobilities in their parent gasesPublication . Neves, P.N.B.; Escada, J.; Borges, F.I.G.M.; Távora, L. M. N.; Conde, C.A.N.The experimental study of the reduced mobility K0 of the molecular ions H3+/H5+ in H 2 and D3+/D5+ in D 2 was carried out using a recently developed technique, that uses a Xe VUV flash lamp and a Gaseous Electron Multiplier (GEM) microstructure with a CsI deposit to produce the molecular ions by electron avalanche ionization. For both gases, the K0 values were obtained at room temperature (295 K) and at pressures from 5 to 50 Torr for uniform reduced electric fields E/N from 4 to 40 Td. The reduced mobility derived from the measurements is an average of the K0 value of the two molecular ions, and for the H 3+ and H5+ ions is 11.1 cm 2V-1s-1 while for D3+ and D5+ it ranges from 8.5 to 7.8 cm2V -1s-1, for pressure from 5 to 50 Torr. A discussion of the obtained results is presented.
- Experimental Measurement of the Ne+ and Ne+2 Mobilities in Ne and the Reaction Rate Coefficient for Ne++2Ne→Ne+2+NePublication . Neves, P.N.B.; Garcia, A. N. C.; Trindade, A. M. F.; Barata, J. A. S.; Távora, L. M. N.; Conde, C. A. N.We measured the reduced mobilities of the atomic, Ne+, and dimer, Ne2+, ions in Ne, under different pressures and reduced electric fields, at 300 K. Extrapolation to zero field yields values of 4.4 cm2 V-1 s-1 for Ne+ and 6.2 cm2 V-1 s-1 for Ne2+, which are in relative good agreement with other published data. The Ne+ ions are converted to Ne2+ by a three-body reaction with a rate constant that was also measured. Its average value for reduced electric fields in the 8 to 12 Td range was (5.6 ± 0.1) × 10-32 cm6 s-1 at 300 K, also agreeing with the results from other authors using other techniques.