Design and Performance of a Magnetic Bottle Electron Spectrometer for High-Energy Photoelectron Spectroscopy

TL;DR

This paper presents a magnetic bottle electron spectrometer with high energy resolution and efficiency, suitable for high-energy photoelectron spectroscopy at XFEL sources, enabling advanced time-resolved measurements.

Contribution

The paper introduces a novel MBES design with a long drift tube and segmented detector, achieving sub-eV resolution and high collection efficiency for high-energy electrons.

Findings

Achieves sub-eV energy resolution for high-energy electrons

Demonstrates high collection efficiency and spatial selectivity

Provides a robust method to remove detection artifacts

Abstract

We describe the design and performance of a magnetic bottle electron spectrometer~(MBES) for high-energy electron spectroscopy. Our design features a ${\sim2}$~m long electron drift tube and electrostatic retardation lens, achieving sub-electronvolt (eV) electron kinetic energy resolution for high energy (several hundred eV) electrons with close to 4$\pi$ collection efficiency. A segmented anode electron detector enables the simultaneous collection of photoelectron spectra in high resolution and high collection efficiency modes. This versatile instrument is installed at the TMO endstation at the LCLS x-ray free-electron laser (XFEL). In this paper, we demonstrate its high resolution, collection efficiency and spatial selectivity in measurements where it is coupled to an XFEL source. These combined characteristics are designed to enable high-resolution time-resolved measurements using x-ray photoelectron, absorption, and Auger-Meitner spectroscopy. We also describe the pervasive artifact in MBES time-of-flight spectra that arises from a periodic modulation in electron detection efficiency, and present a robust analysis procedure for its removal.