# Three Dimensional Polarimetric Neutron Tomography of Magnetic Fields

## TL;DR

This paper introduces a novel neutron tomography technique that non-invasively measures three-dimensional magnetic fields inside bulk materials using time-of-flight polarimetric methods, enabling insights previously difficult to obtain.

## Contribution

The paper presents the first successful demonstration of 3D magnetic field reconstruction using ToF polarimetric neutron tomography with a new setup and tailored algorithm.

## Key findings

- Reconstructed magnetic fields of a current-carrying solenoid.
- Demonstrated high penetration and sensitivity of the technique.
- Reduced measurement time through optimized neutron source timing.

## Abstract

Through the use of Time-of-Flight Three Dimensional Polarimetric Neutron Tomography (ToF 3DPNT) we have for the first time successfully demonstrated a technique capable of measuring and reconstructing three dimensional magnetic field strengths and directions unobtrusively and non-destructively with the potential to probe the interior of bulk samples which is not amenable otherwise. Using a pioneering polarimetric set-up for ToF neutron instrumentation in combination with a newly developed tailored reconstruction algorithm, the magnetic field generated by a current carrying solenoid has been measured and reconstructed, thereby providing the proof-of-principle of a technique able to reveal hitherto unobtainable information on the magnetic fields in the bulk of materials and devices, due to a high degree of penetration into many materials, including metals, and the sensitivity of neutron polarisation to magnetic fields. The technique puts the potential of the ToF time structure of pulsed neutron sources to full use in order to optimise the recorded information quality and reduce measurement time.