Measuring magnetic fields in laser-driven coils with dual-axis proton deflectometry

P. Bradford*, A. Dearling, M. Ehret, L. Antonelli, N. Booth, D. C. Carroll, R. J. Clarke, K. Glize, R. Heathcote, M. Khan, J. D. Moody, S. Pikuz, B. B. Pollock, M. P. Read, S. Ryazantsev, C. Spindloe, C. P. Ridgers, J. J. Santos, V. T. Tikhonchuk, N. C. Woolsey

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


By driving hot electrons between two metal plates connected by a wire loop, high power lasers can generate multi-tesla, quasi-static magnetic fields in miniature coil targets. Many experiments involving laser-coil targets rely on proton deflectometry directed perpendicular to the coil axis to extract a measurement of the magnetic field. In this paper, we show that quantitative measurements using perpendicular probing are complicated by the presence of GV m-1 electric fields in the target that develop on sub-ns timescales. Probing parallel to the coil axis with fiducial grids is shown to reliably separate the electric and magnetic field measurements, giving current estimates of I ≈ 5 kA in 1 mm- and 2 mm-diameter wire loops. An analytic model of proton deflection in electric and magnetic fields is used to benchmark results from the particle-in-cell code and help deconvolve the magnetic and electric field deflections. Results are used to motivate a new experimental scheme that combines a single-plate target with axial proton probing and direct current measurements. This scheme has several important advantages over the traditional target and diagnostic set-up, enabling the robust measurement of coil magnetic fields and plasma properties, as well as making it easier to validate different theoretical models at a range of laser intensities.

Original languageEnglish
Article number084008
Number of pages13
JournalPlasma Physics and Controlled Fusion
Issue number8
Early online date1 Jul 2021
Publication statusPublished - Aug 2021

Bibliographical note

© 2021 The Author(s). Published by IOP Publishing Ltd.


  • coils
  • fields
  • laser
  • magnetic
  • plasma
  • proton deflectometry
  • proton radiography

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