Proton radiography is a widely-fielded diagnostic used to measure magnetic
structures in plasma. The deflection of protons with multi-MeV kinetic energy
by the magnetic fields is used to infer their path-integrated field strength.
Here, the use of tomographic methods is proposed for the first time to lift the
degeneracy inherent in these path-integrated measurements, allowing full
reconstruction of spatially resolved magnetic field structures in three
dimensions. Two techniques are proposed which improve the performance of
tomographic reconstruction algorithms in cases with severely limited numbers of
available probe beams, as is the case in laser-plasma interaction experiments
where the probes are created by short, high-power laser pulse irradiation of
secondary foil targets. The methods are equally applicable to optical probes
such as shadowgraphy and interferometry [M. Kasim et al. Phys. Rev. E 95,
023306 (2017)], thereby providing a disruptive new approach to three
dimensional imaging across the physical sciences and engineering disciplines.Comment: 11 pages, 6 figures, companion article to arXiv:2103.1126
