Ferromagnetic Positron Beam Guidance for Single Shot Measurement in 2D-ACAR Spectrometers

Angular correlation of electron-positron annihilation radiation (ACAR) is a technique to determine the electronic structure of solids. It is based on detecting the annihilation gammas' deviation from collinearity in order to measure the electron momentum before annihilation.
This study deals with the experimental feasibility of single-shot ACAR measurements as a way of efficiently mapping the Fermi surface of crystals with a low electron momentum directions, corresponding to a quasi 2D electronic system.
Single-shot measurements require the sample normal to be aligned with the detector axis, with the positron source being outside the field of view at the same time.
A novel approach of ferromagnetically guiding positrons under high external magnetic field (1.0T) conditions is explored both in simulation and experimentally. Furthermore, new radiographic methods to quickly assay positron beams are evaluated.