Feasibility study of a positron lifetime spectrometer for measurements of porous and polymer films with a DC positron beam

Abstract

Positron Annihilation Lifetime Spectroscopy (PALS) is an increasingly im- portant analysis technique that can be efficiently used to characterize the free volume sizes in porous silica and polymer thin films. In this document a design of a non-expensive lifetime spectrometer to mea- sure positron annihilation lifetime spectra in thin films with a continuous (DC) magnetically guided slow positron beam is described. The system uses sec- ondary electrons emitted from the surface of the sample by the primary positrons in order to generate a START timing signal. Simulation results show that the time resolution can be expected to be . 300 ps at FWHM.