Abstract

A developing application of laser-driven currents is the generation of magnetic fields of picosecond–nanosecond duration with magnitudes exceeding $B=10~\text{T}$ . Single-loop and helical coil targets can direct laser-driven discharge currents along wires to generate spatially uniform, quasi-static magnetic fields on the millimetre scale. Here, we present proton deflectometry across two axes of a single-loop coil ranging from 1 to 2 mm in diameter. Comparison with proton tracking simulations shows that measured magnetic fields are the result of kiloampere currents in the coil and electric charges distributed around the coil target. Using this dual-axis platform for proton deflectometry, robust measurements can be made of the evolution of magnetic fields in a capacitor coil target.

Highlights

  • Capacitor coils are a type of laser-driven solenoid that consists of two metal plates held in parallel, connected by a loop of wire or metallic ribbon[1,2,3]

  • A return current is established along the connecting loop, generating a quasi-static magnetic field that can be used in high energy density physics experiments[2, 7, 8]

  • We have demonstrated dual-axis proton probing of the electromagnetic fields around a capacitor coil target at a laser drive intensity of I ∼ 5 × 1015 W · cm−2

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Summary

Introduction

Capacitor coils are a type of laser-driven solenoid that consists of two metal plates held in parallel, connected by a loop of wire or metallic ribbon[1,2,3]. High-frequency B-dot probes can measure the full time evolution of a capacitor coil magnetic field, but are highly sensitive to electromagnetic pulse noise[20, 21] and must be positioned several centimetres from the target to avoid radiation damage This introduces significant errors in the signal analysis because the magnetic field geometry must be simulated and extrapolated over a long distance. One can check that the electric/magnetic fields required to reproduce an RCF image along one axis are consistent with a different image taken at 90◦ to the first (see Sections 3.2 and 3.5) This allows us to map the magnetic field evolution and dependence on target parameters such as the loop diameter.

Experimental setup
Proton deflectometry
Synthetic proton deflectometry
Perpendicular deflectometry
Perpendicular deflectometry: combined E- and B-field simulations
Axial deflectometry: negative charge distribution
Axial deflectometry: upper limits on capacitor coil magnetic field
Discussion
Conclusion
Full Text
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