Ortho-positronium re-emission yield and energy in surfactant-templated mesoporous silica films

摘要

Measurement of the ortho-positronium (o-Ps) re-emission yield from thin mesoporous silica films into vacuum gives information on the porosity and pore interconnection. In addition, the emitted o-Ps can be used as a target for antiprotons to produce antihydrogen as well as in other experiments which require a high density of o-Ps in vacuum. We studied the re-emission yield from thin surfactant-templated mesoporous silica films deposited on glass. The measurements were performed in reflection mode with a specially designed lifetime spectrometer mounted on a slow positron beam system at CERN. The intensity of the 142 ns vacuum lifetime component was recorded as a function of the energy of the positron beam. Values as high as 40% were found for the re-emission efficiency at low positron energy.