A vacuum-ultraviolet spectropolarimeter for an electron beam ion trap

Area of Science:

• Atomic Physics
• Spectroscopy
• Plasma Physics

Background:

• Multiply charged ions are crucial in astrophysics and fusion research.
• Understanding ion emission polarization provides insights into atomic structure and collision dynamics.
• Electron Beam Ion Traps (EBIT) are powerful tools for studying these ions.

Purpose of the Study:

• To develop and demonstrate a novel vacuum-ultraviolet spectropolarimeter for measuring linear polarization of emission lines from ions in an EBIT.
• To achieve high precision in polarization measurements for benchmarking theoretical models.

Main Methods:

• Utilized a spectropolarimeter with a rotatable MgF2 waveplate and a multilayer-coated reflective polarizer.
• Employed a grazing-incidence grating for wavelength dispersion.
• Measured intensity modulation of spectral lines as the waveplate rotated to determine polarization.

Main Results:

• Successfully measured the linear polarization of the 2s-2p3/2 transition in Li-like N4+ at 124 nm.
• Observed clear intensity modulation, yielding a polarization degree P = -(0.178 ± 0.014).
• Demonstrated the capability for polarization measurements with an absolute uncertainty of ΔP ≈ 0.01.

Conclusions:

• The developed spectropolarimeter is effective for precise polarization measurements of multiply charged ions.
• The instrument serves as a valuable tool for validating magnetic-sublevel-resolved collision theories.
• Results confirm the capability to probe atomic processes in EBITs with high accuracy.