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

Positron Annihilation Lifetime Spectroscopy (PALS)is an increasingly important 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 measure positron annihilation lifetime spectra in thin films with a continuous (DC) magnetically guided slow positron beam is described. The system uses secondary 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 $\lessim$ 300 ps at FWHM.