Guiding of relativistic electron beams in dense matter by laser-driven magnetostatic fields

Intense lasers interacting with dense targets accelerate relativistic electron beams, whichtransport part of the laser energy into the target depth. However, the overall laser-to-targetenergy coupling efficiency is impaired by the large divergence of the electron beam, intrinsicto the laser-plasma interaction. Here we demonstrate that an efficient guiding ofMeV electrons with about 30MA current in solid matter is obtained by imposing a laserdrivenlongitudinal magnetostatic field of 600 T. In the magnetized conditions the transportedenergy density and the peak background electron temperature at the 60-μm-thicktarget's rear surface rise by about a factor of five, as unfolded from benchmarked simulations.Such an improvement of energy-density flux through dense matter paves the ground foradvances in laser-driven intense sources of energetic particles and radiation, driving matter toextreme temperatures, reaching states relevant for planetary or stellar science as yet inaccessibleat the laboratory scale and achieving high-gain laser-driven thermonuclear fusion

Micron-scale mapping of megagauss magnetic fields using optical polarimetry to probe hot electron transport in petawatt-class laser-solid interactions

The transport of hot, relativistic electrons produced by the interaction of an intense petawatt laser pulse with a solid has garnered interest due to its potential application in the development of innovative x-ray sources and ion-acceleration schemes. We report on spatially and temporally resolved measurements of megagauss magnetic fields at the rear of a 50-μm thick plastic target, irradiated by a multi-picosecond petawatt laser pulse at an incident intensity of ~1020 W/cm2. The pump-probe polarimetric measurements with micron-scale spatial resolution reveal the dynamics of the magnetic fields generated by the hot electron distribution at the target rear. An annular magnetic field profile was observed ~5 ps after the interaction, indicating a relatively smooth hot electron distribution at the rear-side of the plastic target. This is contrary to previous time-integrated measurements, which infer that such targets will produce highly structured hot electron transport. We measured large-scale filamentation of the hot electron distribution at the target rear only at later time-scales of ~10 ps, resulting in a commensurate large-scale filamentation of the magnetic field profile. Three-dimensional hybrid simulations corroborate our experimental observations and demonstrate a beam-like hot electron transport at initial time-scales that may be attributed to the local resistivity profile at the target rear

Alternative ignition schemes in inertial confinement fusion

This paper presents a short overview of a series of review articles describing alternative approaches to ignition of fusion reactions in inertially confined plasmas. © 2014 IAEA, Vienna

Fast electron energy transport in solid density and compressed plasma

We provide a review of selected experiments on fast electron transport in solids and plasmas following laser-matter interaction at relativistic intensities. Particular attention is given to precise measurements of intense laser pulses, fast electron energy transfer and the mean kinetic energy of the fast electrons. We discuss in detail mechanism of fast electron energy loss in solid and warm dense targets. We show that stopping due to resistive electric field and collimation due to resistive magnetic field play significant roles in fast electron dynamics. It has also been shown that reducing the size of the target can significantly affect the K production from the targets. The use of reduced-mass target can also increase temperature up to 1keV level, which provides an excellent platform for fast electron transport without assembling the fuel. The pre-pulse is a significant issue in fast ignition for fast electron coupling to the compressed core. Indeed, we have shown using a variety of targets that the laser pre-pulse can significantly reduce transfer of energy farther into the target. In this article, we show that a significant progress has been made in understanding the critical issues of fast electron transport pertinent to fast ignition (FI). This understanding will facilitate a better target design for large scale FI integrated experiments when laser facilities become available. © 2014 IAEA, Vienna

Fast electron energy transport in solid density and compressed plasma

We provide a review of selected experiments on fast electron transport in solids and plasmas following laser-matter interaction at relativistic intensities. Particular attention is given to precise measurements of intense laser pulses, fast electron energy transfer and the mean kinetic energy of the fast electrons. We discuss in detail mechanism of fast electron energy loss in solid and warm dense targets. We show that stopping due to resistive electric field and collimation due to resistive magnetic field play significant roles in fast electron dynamics. It has also been shown that reducing the size of the target can significantly affect the K production from the targets. The use of reduced-mass target can also increase temperature up to 1keV level, which provides an excellent platform for fast electron transport without assembling the fuel. The pre-pulse is a significant issue in fast ignition for fast electron coupling to the compressed core. Indeed, we have shown using a variety of targets that the laser pre-pulse can significantly reduce transfer of energy farther into the target. In this article, we show that a significant progress has been made in understanding the critical issues of fast electron transport pertinent to fast ignition (FI). This understanding will facilitate a better target design for large scale FI integrated experiments when laser facilities become available. © 2014 IAEA, Vienna