Nanochanneled silicon targets with high positron/positronium (Ps) conversion rate and efficient Ps cooling were produced. Morphological parameters of the nanochannels, such as their diameter and length, were adjusted to get a large fraction of thermalized Ps at room temperature being emitted into vacuum. Ps cooling measurements were conducted combining single-shot positron annihilation lifetime spectroscopy and Doppler spectroscopy of the 1(3)S -> 2(3)P transition. 2 gamma-3 gamma annihilation ratio measurements were also performed to estimate the positron/Ps conversion efficiency. In a converter with nanochannel diameter of 7-10 nm and depth of 3.89 mu m, similar to 28% of implanted positrons with an energy of 3.3 keV was found to be emitted as Ps with a transverse kinetic energy of 11 +/- 2 meV. The reduction of the nanochannels depth to 1.13 mu m, without changing the nanochannel diameter, was found to result in a less efficient cooling, highlighting the presence of Ps reflection from the bottom end of nanochannels.

High-yield thermalized positronium at room temperature emitted by morphologically tuned nanochanneled silicon targets / S. Mariazzi, R. Caravita, C. Zimmer, B. Rienäcker, A. Camper, A. Belov, G. Bonomi, R.S. Brusa, F. Castelli, G. Consolati, M. Doser, H. Gjersdal, L.T. Glöggler, F. Guatieri, S. Haider, V. Matveev, G. Nebbia, P. Nedelec, D. Pagano, L. Penasa, V. Petracek, F. Prelz, L. Povolo, O.M. Rhøne, A. Rotondi, H. Sandaker, N. Zurlo. - In: JOURNAL OF PHYSICS. B, ATOMIC MOLECULAR AND OPTICAL PHYSICS. - ISSN 0953-4075. - 54:8(2021 Apr), pp. 085004.1-085004.11. [10.1088/1361-6455/abf6b6]

High-yield thermalized positronium at room temperature emitted by morphologically tuned nanochanneled silicon targets

F. Castelli;F. Prelz;
2021-04

Abstract

Nanochanneled silicon targets with high positron/positronium (Ps) conversion rate and efficient Ps cooling were produced. Morphological parameters of the nanochannels, such as their diameter and length, were adjusted to get a large fraction of thermalized Ps at room temperature being emitted into vacuum. Ps cooling measurements were conducted combining single-shot positron annihilation lifetime spectroscopy and Doppler spectroscopy of the 1(3)S -> 2(3)P transition. 2 gamma-3 gamma annihilation ratio measurements were also performed to estimate the positron/Ps conversion efficiency. In a converter with nanochannel diameter of 7-10 nm and depth of 3.89 mu m, similar to 28% of implanted positrons with an energy of 3.3 keV was found to be emitted as Ps with a transverse kinetic energy of 11 +/- 2 meV. The reduction of the nanochannels depth to 1.13 mu m, without changing the nanochannel diameter, was found to result in a less efficient cooling, highlighting the presence of Ps reflection from the bottom end of nanochannels.
positronium; cooling; silicon; nanostructures
Settore FIS/01 - Fisica Sperimentale
Settore FIS/03 - Fisica della Materia
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/850283
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