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Photoelectron angular distribution as a versatile polarization analyzer for soft and tender X-rays

Yoshiyuki Ohtsubo, Hiroaki Kimura

Abstract

The polarization of soft and tender X-rays serves as a widely utilized probe for investigating diverse physical properties, such as magnetic order in materials. However, experimental methods for determining the polarization of tender X-rays (1.5-3.0 keV) have remained limited. In this work, we propose a polarization measurement method for this energy range based on the photoelectron angular distribution. The angular distribution of photoelectrons emitted from carbon targets was measured using linearly polarized synchrotron radiation. The results showed a clear dependence on the incident photon polarization across the energy range of 0.4 to 3.0 keV. This demonstrates that the photoelectron angular distribution can serve as a reliable tool for determining the linear polarization of soft and tender X-ray photons, facilitating the development of polarization-dependent measurements across this broad energy range.

Photoelectron angular distribution as a versatile polarization analyzer for soft and tender X-rays

Abstract

The polarization of soft and tender X-rays serves as a widely utilized probe for investigating diverse physical properties, such as magnetic order in materials. However, experimental methods for determining the polarization of tender X-rays (1.5-3.0 keV) have remained limited. In this work, we propose a polarization measurement method for this energy range based on the photoelectron angular distribution. The angular distribution of photoelectrons emitted from carbon targets was measured using linearly polarized synchrotron radiation. The results showed a clear dependence on the incident photon polarization across the energy range of 0.4 to 3.0 keV. This demonstrates that the photoelectron angular distribution can serve as a reliable tool for determining the linear polarization of soft and tender X-ray photons, facilitating the development of polarization-dependent measurements across this broad energy range.
Paper Structure (4 sections, 2 equations, 3 figures, 2 tables)

This paper contains 4 sections, 2 equations, 3 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Methods
  3. Results and discussion
  4. Summary

Figures (3)

  • Figure 1: (a) A schematic drawing of the polarization measurement using a multilayer reflection target and a rotating analyzer. (b) The same as (a), but utilizing photoelectrons emitted from the target. In both cases, the target and the micro-channel plate (MCP) detector rotate around the incident beam axis, and the MCP signals are recorded as a function of the rotation angle $\chi$. (c) Circuit diagram for the MCP detector. The resistances are $R_1$ = 2 M$\Omega$ and $R_2$ = 0.1 M$\Omega$.
  • Figure 2: (a) MCP anode current as a function of $\chi$ (circles) measured using tender X-ray synchrotron radiation ($h\nu$ = 2000 eV). The incident beam is polarized along the linear horizontal orientation. A solid curve is the fitting result (see the main text for details). The contrast factor ($C$) obtained by the fitting is 0.71. (b) Contrast factors obtained from the MCP anode currents with $\chi$ rotation at various incident photon energies with linear polarization. Arrows indicate the data shown in Fig. \ref{['fig3']}.
  • Figure 3: (a, b) MCP anode current as a function of $\chi$ measured with (open circles) and without (filled circles) applying a sample bias voltage. The incident beam is polarized along the linear vertical orientation. Solid and dashed curves represent the fitting results obtained using Eq. (\ref{['eq:ELLI']}). (c) Contrast factors as a function of incident photon energy, measured with sample biases ranging from -1.1 to -0.25 kV to obtain sufficient MCP anode current around 100 pA.