Time bunching of slow positrons for lifetime and time-of-flight measurements of ortho-positronium

On the basis of velocity modulation, we have developed a positron-beam buncher for the measurement of ortho-positronium lifetime τo−Ps and TOF. Since high permeability cores were used, the buncher was constructed compactly and was used to efficiently produce a bunched beam with a bunch width of 2.2 ns (FWHM) and a repetition period of 960 ns. We have measured the lifetime of ortho-positronium using the buncher and obtained τo−Ps=127 ns. In this paper, we report on the technical details and performance of the buncher.