Charge-displacement Self-channeling Research Articles

Ion dynamics and coherent structure formation following laser pulse self-channeling

The propagation of a superintense laser pulse in an underdense, inhomogeneous plasma has been studied numerically by two-dimensional particle-in-cell simulations on a time scale extending up to several picoseconds. The effects of the ion dynamics following the charge-displacement self-channeling of the laser pulse have been addressed. Radial ion acceleration leads to the ‘breaking’ of the plasma channel walls, causing an inversion of the radial space-charge field and the filamentation of the laser pulse. At later times a number of long-lived, quasi-periodic field structures are observed and their dynamics is characterized with high resolution. Inside the plasma channel, a pattern of electric and magnetic fields resembling both soliton- and vortex-like structures is observed.

Laser Wakefield in Low Density Plasma

The laser wakefiled (LWF) and the relativistic and charge-displacement self-channeling in the comparatively low density plasma were studied. The dynamics of the electron plasma wave (EPW) in LWF was experimentally observed at the electron density of ∼10 16 cm -3 . The two dimensional instantaneous image of EPW was also obtained. The asymmetric 2D image was explained by the modified liner theory. These experimental results suggest that the intensity of ∼10 18 W/cm 2 was achieved in the low density static gas target. This means the possibility of not only the coherent control of EPW, but also the long relativistic and charge-displacement self-channeling with the low density static gas. For the self-channeling, the simple model tells us that the long channel without defocusing could be possible with a tens of TW, ps glass laser system.

Observation of relativistic and charge-displacement self-channeling of intense subpicosecond ultraviolet (248 nm) radiation in plasmas.

Experimental studies examining a anew relativistic regime of high-intensity short-pulse propagation in plasmas have been performed which present evidence for the formation of a stable mode of spatially confined (channeled) propagation. For an electron density of \ensuremath{\sim}1.35\ifmmode\times\else\texttimes\fi{}${10}^{21}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ and a power of \ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}${10}^{11}$ W, the results indicate a channel radius ,1 \ensuremath{\mu}m and a peak intensity \ensuremath{\sim}${10}^{19}$ W ${\mathrm{cm}}^{2}$. Comparison of these findings with a dynamical theory yields agreement for both the longitudinal structure and the radial extent of the propagation observed.

Relativistic and charge-displacement self-channeling of intense ultrashort laser pulses in plasmas.

Relativistic and charge-displacement self-channeling is one of the most significant phenomena in the entire area of the interactions of extremely intense laser pulses with matter. Both the relativistic increase in the mass of laserdriven plasma electrons and the reduction of electron concentration under the effect of the ponderomotive force tend to reduce the local electron frequency in a laser-irradiated plasma. As a result, the simultaneous modification of the plasma dielectric response by the propagating electromagnetic radiation via the above two mechanisms enhances the medium transparency in the paraxial domain where the intensity is maximal. Under certain conditions discussed in this chapter, this effect leads to the emergence of channeled regimes of superintense laser pulse propagation in underdense plasmas. In these regimes, the laser radiation diffraction is suppressed, nonlinear beam self-trapping occurs, and the laser pulse propagates into the plasma over dozens of Rayleigh ranges. An additional electromagnetic radiation confinement mechanism emerges due to electron cavitation, namely, the total expulsion of the electron fluid from a certain spatial area. Then, the laser beam propagates within the resulting channel, where the intensities can reach the level of 1022 W/cm2.

Prospects for X-ray amplification with charge-displacement self-channeling

The authors develop an analytic theory of charge-displacement self-channeling, a mechanism that can dynamically trap a short intense pulse of light. Attention is focused on the case of most interest for X-ray amplification: the strongly saturated channel, for which all free electrons are expelled from the channel core and the channel walls are overdense. Some curious results are: (1) the intensity at the channel walls is independent of the total laser power, (2) the radius of the channel increases very slowly with laser power, asymptotically as the fourth root, and (3) the power in the channel wall is a constant. It is also found that the channel is an effective waveguide for all secondary radiation. Scaling studies show that there is a substantial advantage in using the highest-frequency driving laser available. The channel is ideal for generating coherent short-wavelength radiation, perhaps well into the X-ray range. >