Ultrafast proton radiography of the magnetic fields generated by a laser-driven coil current

Abstract

Magnetic fields generated by a current flowing through a U-shaped coil connecting two copper foils were measured using ultrafast proton radiography. Two ∼1.25 kJ, 1-ns laser pulses propagated through laser entrance holes in the front foil and were focused to the back foil with an intensity of ∼3 × 1016 W/cm2. The intense laser-solid interaction induced a high voltage between the copper foils and generated a large current in the connecting coil. The proton data show ∼40–50 T magnetic fields at the center of the coil ∼3–4 ns after laser irradiation. The experiments provide significant insight for future target designs that aim to develop a powerful source of external magnetic fields for various applications in high-energy-density science.

Enhanced proton acceleration in an applied longitudinal magnetic field

“…Our study highlights how such a strong magnetic field can improve characteristics of laser-driven proton beams, which is a strong motivation for further development of laser-driven magnetic field capabilities. As shown in previous experiments [10,11,34], these fields quickly rise on a sub-ns time scale and then slowly decay on time scales typically exceeding 10 ns. The 10 ns time period corresponds to a penetration depth of about 10 μm in copper-like-conductive materials.…”

“…Even though the required kT-level magnetic fields are currently out of reach, they are likely to become feasible due to the ongoing rapid progress in generating magnetic fields with laser-driven coils using ns-long laser pulses [10,11,34]. Our study highlights how such a strong magnetic field can improve characteristics of laser-driven proton beams, which is a strong motivation for further development of laser-driven magnetic field capabilities.…”

“…Recently, a significant progress has been made in generating strong magnetic fields with laser-driven coils using ns-long laser pulses [10][11][12]. In the context of proton and ion acceleration, such fields can be viewed as static and nearly uniform.…”

Quasistationary magnetic field generation with a laser-driven capacitor-coil assembly

“…Experiments in the domain of higher laser energies and shorter wavelengths of 0.35 µm were reported in Refs. [10,11]. The authors of Ref.…”

“…The authors of Ref. [10] used two Omega EP laser beams with the total energy of 2.5 kJ in a 1 ns pulse and with the intensity 3 × 10 16 W/cm 2 . The maximum magnetic eld measured in the center of an U-shaped loop with a curvature radius of 0.3 mm was at the level of 40 T. The measurements were accomplished with two diagnostics: the B-dot probes and proton deectometry.…”