Abstract
In order to understand the transport of fast electrons within solid density targets driven by an optical high power laser, we have numerically investigated the dynamics and structure of strong self-generated magnetic fields in such experiments. Here we present a systematic study of the bulk magnetic field generation due to the ponderomotive current, Weibel-like instability and resistivity gradient between two solid layers. Using particle-in-cell simulations, we observe the effect of varying the laser and target parameters, including laser intensity, focal size, incident angle, preplasma scale length, target thickness and material and experimental geometry. The simulation results suggest that the strongest magnetic field is generated with laser incident angles and preplasma scale lengths that maximize laser absorption efficiency. The recent commissioning of experimental platforms equipped with both optical high power laser and X-ray free electron laser (XFEL), such as European XFEL-HED, LCLS-MEC and SACLA beamlines, provides unprecedented opportunities to probe the self-generated bulk magnetic field by X-ray polarimetry via Faraday rotation with simultaneous high spatial and temporal resolution. We expect that this systematic numerical investigation will pave the way to design and optimize near future experimental setups to probe the magnetic fields in such experimental platforms.
Highlights
When a high power laser pulse interacts with a solid density target, large numbers of bound electrons are rapidly ionized by the strong laser field[1,2,3,4]
In order to design experimental setups that maximize the field generated, we will describe the effect of different laser parameters (Section 3.2) and target parameters (Section 3.3) on the bulk magnetic field arising from the ponderomotive-driven direct current (DC) current, the Weibel-like instabilities and the plasma resistivity mismatch of multilayer target, calculated from PIC simulations
We have systematically investigated the bulk magnetic field generation inside a solid target irradiated by a short high power laser using numerical simulations
Summary
When a high power laser pulse interacts with a solid density target, large numbers of bound electrons are rapidly ionized by the strong laser field[1,2,3,4]. To probe the bulk magnetic fields within overdense or solid density plasmas, the deflectometry of energetic charged particles such as electron and protons crossing the fields has recently been developed, by taking advantage of the long attenuation length of energetic charged particles in solid density plasmas[23, 24]. We have recently proposed probing the bulk magnetic fields inside the solid density plasmas by X-ray polarimetry via Faraday rotation using X-ray free electron lasers (XFELs), taking advantage of simultaneous high spatial–temporal resolution and several tens of micrometers attenuation length in solid[9]. We aim to optimize the chances of observing the polarization rotation by finding the laser and target parameters that maximize the magnetic field strength
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