Generation of a bunched positron beam extracted nonadiabatically from a buffer-gas trap and focused in a free field region

Abstract

Advanced spectroscopy experiments and new physics experiments with positronium atoms in vacuum will benefit from positronium production in an environment free of magnetic and electrostatic fields. Here, we present a novel scheme for generating a bunched positron beam. The positron bunches are prebunched before extraction from a buffer-gas trap, nonadiabatically extracted from a 700 G magnetic field, energy elevated up to 20 kV, and bunched on a target in a free field. According to simulations of the system, 60% of cooled positrons in the buffer-gas trap are extracted and focused on the target in a time spread of 2.5 ns full width tenth maximum (FWTM) and a spot of about 4 mm FWTM for positron implantation energy higher than 3 keV. These performance numbers are achieved in the same apparatus through a combination of several innovative beam manipulations.