Prototype of an angular-selective photoelectron calibration source for the KATRIN experiment

TL;DR

This paper presents a prototype photoelectron source with narrow energy spread and angular selectivity, crucial for calibrating the KATRIN spectrometer to improve neutrino mass measurements.

Contribution

It introduces a novel angular-selective photoelectron source prototype designed for precise spectrometer calibration in neutrino mass experiments.

Findings

Achieved narrow energy spread in photoelectron emission.

Demonstrated effective angular selectivity via electric and magnetic fields.

Provides a calibration tool for high-resolution spectrometers.

Abstract

The method of direct neutrino mass determination based on the kinematics of tritium beta decay, which is adopted by the KATRIN experiment, makes use of a large, high-resolution electrostatic spectrometer with magnetic adiabatic collimation. In order to target a sensitivity on the neutrino mass of 0.2 eV/c^2, a detailed understanding of the electromagnetic properties of the electron spectrometer is essential, requiring comprehensive calibration measurements with dedicated electron sources. In this paper we report on a prototype of a photoelectron source providing a narrow energy spread and angular selectivity. Both are key properties for the characterisation of the spectrometer. The angular selectivity is achieved by applying non-parallel strong electric and magnetic fields: Directly after being created, photoelectrons are accelerated rapidly and non-adiabatically by a strong electric field before adiabatic magnetic guiding takes over.