Abstract:We demonstrate a novel plasma device for magnetic reconnection, driven by Gekko XII lasers irradiating a double-turn Helmholtz capacitor-coil target. Optical probing revealed an accumulated plasma plume near the magnetic reconnection outflow. The background electron density and magnetic field were measured to be approximately 1018 cm−3 and 60 T by using Nomarski interferometry and the Faraday effect, respectively. In contrast with experiments on magnetic reconnection constructed by the Biermann battery effect,… Show more
“…Similar targets made out of Ni were previously studied using an optical probe. 35 By contrast, in our study, ultrafast proton radiography of the reconnection geometry was performed to characterize the platform. The proton data show two prolate voids due to proton deflections by the currents in the coils, from which $31-44 kA currents in each coil at $3-6 ns after laser irradiation were inferred.…”
Section: Introductionmentioning
confidence: 95%
“…A robust platform for generating strong external magnetic fields has emerged more recently using intense lasers and a unique capacitor-coil target. First introduced by Korobkin 28 in 1979, the technique has been developed by many groups [29][30][31][32][33][34][35][36][37][38] and provides a reliable method to generate up to kiloTesla magnetic fields. 39,40 Such capacitor coil targets are generally composed of two parallel metallic plates (the capacitor) connected with thin wires in different geometric shapes.…”
A novel magnetically driven reconnection platform was created by a pair of U-shaped Cu coils that connect two parallel Cu plates irradiated at a focused laser intensity of $3 Â 10 16 W/cm 2 and characterized using ultrafast proton radiography. The proton data show two prolate voids, each corresponding to the coil current, with an inferred maximum magnitude of 57 6 4 kA. A center "flasklike" feature was also observed in the proton radiographs. By prescribing electromagnetic fields associated with magnetic reconnection in proton ray tracing simulations, characteristics of this center feature were reproduced. These results demonstrate the robustness of the laser-driven capacitor coils for generating strong magnetic fields and provide promise of using such coils as a viable platform for studying magnetically driven reconnection in the laboratory.
“…Similar targets made out of Ni were previously studied using an optical probe. 35 By contrast, in our study, ultrafast proton radiography of the reconnection geometry was performed to characterize the platform. The proton data show two prolate voids due to proton deflections by the currents in the coils, from which $31-44 kA currents in each coil at $3-6 ns after laser irradiation were inferred.…”
Section: Introductionmentioning
confidence: 95%
“…A robust platform for generating strong external magnetic fields has emerged more recently using intense lasers and a unique capacitor-coil target. First introduced by Korobkin 28 in 1979, the technique has been developed by many groups [29][30][31][32][33][34][35][36][37][38] and provides a reliable method to generate up to kiloTesla magnetic fields. 39,40 Such capacitor coil targets are generally composed of two parallel metallic plates (the capacitor) connected with thin wires in different geometric shapes.…”
A novel magnetically driven reconnection platform was created by a pair of U-shaped Cu coils that connect two parallel Cu plates irradiated at a focused laser intensity of $3 Â 10 16 W/cm 2 and characterized using ultrafast proton radiography. The proton data show two prolate voids, each corresponding to the coil current, with an inferred maximum magnitude of 57 6 4 kA. A center "flasklike" feature was also observed in the proton radiographs. By prescribing electromagnetic fields associated with magnetic reconnection in proton ray tracing simulations, characteristics of this center feature were reproduced. These results demonstrate the robustness of the laser-driven capacitor coils for generating strong magnetic fields and provide promise of using such coils as a viable platform for studying magnetically driven reconnection in the laboratory.
Laser-driven magnetic reconnection (LDMR) occurring with self-generated B fields has been experimentally and theoretically studied extensively, where strong B fields of more than megagauss are spontaneously generated in high-power laser–plasma interactions, which are located on the target surface and produced by non-parallel temperature and density gradients of expanding plasmas. For properties of the short-lived and strong B fields in laser plasmas, LDMR opened up a new territory in a parameter regime that has never been exploited before. Here we review the recent results of LDMR taking place in both high and low plasma beta environments. We aim to understand the basic physics processes of magnetic reconnection, such as particle accelerations, scale of the diffusion region, and guide field effects. Some applications of experimental results are also given especially for space and solar plasmas.
“…Over the past decade there has been significant effort and progress in developing laserdriven plasma experiments into a platform for studying the dynamics of reconnection in a controlled laboratory setting [12][13][14][15][16][17][18][19][20][21][22][23] . By focusing kilojoule per nanosecond lasers onto solid targets, expanding plasma plumes are ablated, and reconnection can occur between selfgenerated Biermann battery [24][25][26][27] fields or externally imposed magnetic fields 18 .…”
Magnetic reconnection is a fundamental plasma process that is thought to play a key role in the production of nonthermal particles associated with explosive phenomena in space physics and astrophysics. Experiments at high-energy-density facilities are starting to probe the microphysics of reconnection at high Lundquist numbers and large system sizes. We have performed particle-in-cell (PIC) simulations to explore particle acceleration for parameters relevant to laser-driven reconnection experiments. We study particle acceleration in large system sizes that may be produced soon with the most energetic laser drivers available, such as at the National Ignition Facility. In these conditions, we show the possibility of reaching the multi-plasmoid regime, where plasmoid acceleration becomes dominant. Our results show the transition from X point to plasmoid-dominated acceleration associated with the merging and contraction of plasmoids that further extend the maximum energy of the power-law tail of the particle distribution for electrons. We also find for the first time a system-sizedependent emergence of nonthermal ion acceleration in driven reconnection, where the magnetization of ions at sufficiently large sizes allows them to be contained by the magnetic field and energized by direct X point acceleration. For feasible experimental conditions, electrons and ions can attain energies of max,e /k B T e > 100 and max,i /k B T i > 1000. Using PIC simulations with binary Monte Carlo Coulomb collisions we study the impact of collisionality on plasmoid formation and particle acceleration. The implications of these results for understanding the role reconnection plays in accelerating particles in space physics and astrophysics are discussed.
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