Prepulse effects on the generation of high energy electrons in fast ignition scheme

Cai, Hong-bo; Mima, Kunioki; Sunahara, Atsushi; Johzaki, Tomoyuki; Nagatomo, Hideo; Zhu, Shao-ping; He, X. T.

doi:doi:10.1063/1.3299348

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Supra-bubble regime for laser acceleration of cold electron beams in tenuous plasma

Relativistic electrons can be accelerated by an ultraintense laser pulse in the “supra-bubble” regime, that is, in the blow-out regime ahead of the plasma bubble (as opposed to the conventional method, when particles remain inside the bubble). The acceleration is caused by the ponderomotive force of the pulse, via the so-called snow-plow mechanism. The maximum energy gain, Δγ ∼ γga, is attained when the particle Lorentz factor γ is initially about γg/a, where γg is the pulse group speed Lorentz...

Beam collimation and transport of quasineutral laser-accelerated protons by a solenoid field

This article reports about controlling laser-accelerated proton beams with respect to beam divergence and energy. The particles are captured by a pulsed high field solenoid with a magnetic field strength of 8.6 T directly behind a flat target foil that is irradiated by a high intensity laser pulse. Proton beams with energies around 2.3 MeV and particle numbers of 1012 could be collimated and transported over a distance of more than 300 mm. In contrast to the protons the comoving electrons are s...

The energy distribution of the produced high energy electrons in the interaction of ultraintense picosecond laser pulses with high-Z solid targets is shown to be sensitive to the preformed plasma created by the prepulse and the amplified spontaneous emission pedestal. The created preformed plasmas, which are obtained by radiation hydrodynamic simulations for the present heating laser system at ILE, Osaka University, are seen to extend up to 30–100 μm just before the arrival of the main pulse. The dependences of the coupling efficiency of the laser energy to high energy electrons, and the energy spectra of these accelerated electrons, on this preformed plasma, are studied via a two-dimensional particle-in-cell simulation code. It is found that in a small preformed plasma case, J×B heating is dominant and the produced electron temperature agrees well with Haines’ scaling law [ Haines et al., Phys. Rev. Lett., 102, 045008 (2009) ]. While in a large preformed plasma case, in addition to J×B heating and/or vacuum heating, other acceleration mechanisms, such as stochastic heating, can accelerate electrons to very high energies, carrying a significant fraction of input laser energy. Even after several picoseconds, the number of high energy electrons (0.5 MeV<E<5 MeV) generated in a small preformed plasma case can be several times larger than that of a large preformed plasma case.

Article Outline

INTRODUCTION
RADIATION HYDRODYNAMIC SIMULATIONS AND PIC SIMULATION MODELING
PIC SIMULATIONS ON THE GENERATION OF HIGH ENERGY ELECTRONS
GENERATION MECHANISMS FOR THE HIGH ENERGY ELECTRONS
ELECTRON BEAMS FOR FAST IGNITION
SUMMARY AND DISCUSSION

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KEYWORDS and PACS

Keywords

ignition, plasma accelerators, plasma heating by laser, plasma production by laser, plasma simulation

PACS

52.50.Jm

Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.65.Rr

Particle-in-cell method
52.38.Kd

Laser-plasma acceleration of electrons and ions

ARTICLE DATA

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http://dx.doi.org/10.1063/1.3299348

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1070-664X (print)

1089-7674 (online)

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American Institute of Physics

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