Total-Reflection High-Energy Positron Diffractometer at NEPOMUC -- Instrumentation, Simulation and First Measurements

TL;DR

This paper details the development and initial testing of a high-energy positron diffractometer at NEPOMUC, including instrumentation, simulation, and first experimental measurements of beam characteristics.

Contribution

It introduces a novel positron diffractometer setup with optimized beam optics and demonstrates initial experimental validation of beam diameter and system performance.

Findings

Beam diameter of less than 1.3 mm for 10 keV twofold remoderated beam

Simulation results agree with experimental measurements

Successful system tuning and characterization during initial beamtime

Abstract

We report the instrumentation of a new positron diffractometer that is connected to the high-intensity positron source NEPOMUC. Crucial elements for the adaption of the positron beam are presented, which include the magnetic field termination, the optional transmission-type remoderator for brightness enhancement and the electrostatic system for acceleration and beam optics. The positron trajectories of the remoderated and the twofold remoderated beam have been simulated to optimize the system, i.e. to obtain a coherent beam of small diameter. Within a first beamtime we tuned the system and characterized the direct beam. For the twofold remoderated beam of 10keV energy, we experimentally observe a beam diameter of d < 1.3mm, which agrees well with the simulation.