Production and Applications of Intense Pulsed, Slow Positron Beams

Positron annihilation lifetime spectroscopy (PALS) is an experimental technique whereby the lifetime spectrum of positrons injected into a material is measured. Analysis of this spectrum can be used to characterize defects in the material. While radioisotope positron sources are often used for PALS, there are several advantages of using mono-energetic, slow positron beams. In order to measure lifetime spectra with such beams it is necessary to produce a pulsed beam with an extremely short pulse length (~ 200 ps). In this article we discuss the advantages of using pulsed, slow-positron beams, the various methods of beam production and pulsing methods. We focus in particular on intense beams generated by electron accelerators and describe the current status and future plans for the accelerator based facility at AIST.