Collimated fast electron beam generation in critical density plasma

Abstract

Significantly collimated fast electron beam with a divergence angle 10° (FWHM) is observed when an ultra-intense laser pulse (I = 1014 W/cm2, 300 fs) irradiates a uniform critical density plasma. The uniform plasma is created through the ionization of an ultra-low density (5 mg/c.c.) plastic foam by X-ray burst from the interaction of intense laser (I = 1014 W/cm2, 600 ps) with a thin Cu foil. 2D Particle-In-Cell (PIC) simulation well reproduces the collimated electron beam with a strong magnetic field in the region of the laser pulse propagation. To understand the physical mechanism of the collimation, we calculate energetic electron motion in the magnetic field obtained from the 2D PIC simulation. As the results, the strong magnetic field (300 MG) collimates electrons with energy over a few MeV. This collimation mechanism may attract attention in many applications such as electron acceleration, electron microscope and fast ignition of laser fusion.

Density and temperature characterization of long-scale length, near-critical density controlled plasma produced from ultra-low density plastic foam

“… 12 where cylindrical irradiation of the cylinder by high-power lasers was used to ionize the foam. We have also used the same target concept where longitudinal ionization of the foam was performed to produce the plasma medium used for laser propagation studies 14 .…”

“…In this paper, we report on the characterization (density, temperature, and uniformity in 2-D), as achieved by x-ray 15 and proton 16 17 radiography, of the plasma that is contained within the cylinder and that was used in the study of ref. 14 . The plasma that is heated and confined in the cylinder has temperatures of 5–10 eV and electron density around 10 21 cm −3 (which is tunable by adjusting the density of the foam filling the cylinder).…”

A review of low density porous materials used in laser plasma experiments

“…Low density foam targets on the other hand, have a well defined geometry and density before laser illumination, and these have been used for laser-plasma interactions, 2,14,15 the study of laser shock measurements, [16][17][18] thermal smoothing effect, [19][20][21][22] quantum beam generation, 3,23 coulomb explosion, 24 and laboratory astrophysics. 25,26 Additionally, low density foams have been utilized as a mold of cryogenic targets.…”

Backward-ion acceleration in critical density plasmas

“…One side of the opening of the tube is covered by a thin Cu foil (700 nm). A nanosecond-pulse laser irradiates on the foil to generate a homogenous critical density plasma [15,16]; the corresponding plasma density is approximately one and two times that of the critical density for 1.054 µm laser light.…”

“…Then, the Ponderomotive potential and pressure gradient (−∇p e ) at the pulse front accelerate electrons in the reflected light direction; this results in the formation of an electrostatic field which accelerates plasma ions in the backward direction. Simultaneously, the azimuthal magnetic field generated in the plasma by forward-accelerated electrons [15] reduces the beam divergence of the backward-accelerated ions.…”