Proton deflectometry with in situ x-ray reference for absolute measurement of electromagnetic fields in high-energy-density plasmas

TL;DR

This paper introduces a proton deflectometry technique using in situ x-ray references for precise magnetic field measurements in high-energy-density plasmas, enabling accurate analysis of plasma-magnetic field interactions.

Contribution

The paper presents a novel proton deflectometry method with in situ x-ray references and automated data analysis algorithms for improved magnetic field measurements in plasmas.

Findings

Successfully measured non-uniform magnetic fields in vacuum.

Observed plasma plume interaction with magnetic fields.

Validated the technique at the OMEGA facility.

Abstract

We report a technique of proton deflectometry which uses a grid and an in situ reference x-ray grid image for precise measurements of magnetic fields in high-energy density plasmas. A D$^3$He fusion implosion provides a bright point-source of both protons and x-rays, which is split into beamlets by a mesh grid. The protons undergo deflections as they propagate through the plasma region of interest, whereas the x-rays travel along straight lines. The x-ray image therefore provides a zero-deflection reference image. The line-integrated magnetic fields are inferred from the shifts of beamlets between the deflected (proton) and reference (x-ray) images. We developed a system for analysis of this data, including automatic algorithms to find beamlet locations and calculate their deflections from the reference image. The technique is verified in an experiment performed at OMEGA to measure a non-uniform magnetic field in vacuum, then applied to observe the interaction of an expanding plasma plume with the magnetic field.