Energy-Conserving Theory of the Blowout Regime of Plasma Wakefield.

We present a self-consistent theory of strongly nonlinear plasma wakefield (bubble or blowout regime of the wakefield) based on the energy conservation approach. Such wakefields are excited in plasmas by intense laser or particle beam drivers and are characterized by the expulsion of plasma electrons from the propagation axis of the driver. As a result, a spherical cavity devoid of electrons (called a "bubble") and surrounded by a thin sheath made of expelled electrons is formed behind the driver.

A Study on the Behavior of Cadmium in the Soil Solution-Plant System by the Lysimeter Method Using the Cd Radioactive Tracer.

In soils, cadmium (Cd) and its compounds, originating from industrial activities, differ both in mobility as well as in their ability to permeate the soil solution from naturally occurring cadmium compounds (native Cd). Therefore, the determination of the parameters of cadmium mobility in soils and its accumulation by plants in the soil-soil solution-plant system is very important from both scientific and practical viewpoints. Cd was used as a radioactive tracer to study the processes of the transition of Cd into the aqueous phase and its uptake by plants over the course of a vegetative lysimeter experiment.

Settlement of Soil Reinforced with Vertical Fiberglass Micro-Piles.

This article is dedicated to investigating the properties of soil after its reinforcement with fiberglass elements through large-scale laboratory plate-load tests of various samples that varied in the numbers and lengths of the reinforcing elements. The investigation of the vertical elements considered the diameter increase at the bottom toe by using widening washers. The results were compared relative to each other and to the theoretical calculation results.

Positron acceleration via laser-augmented blowouts in two-column plasma structures.

We propose a setup for positron acceleration consisting of an electron driver and a laser pulse creating a twofold plasma column structure. The resulting wakefield is capable of accelerating positron bunches over long distances even when the evolution of the driver is considered. The scheme is studied by means of particle-in-cell simulations.

Efficient Narrow-Band Terahertz Radiation from Electrostatic Wakefields in Nonuniform Plasmas.

It is shown that electrostatic plasma wakefields can efficiently radiate at harmonics of the plasma frequency when the plasma has a positive density gradient along the propagation direction of a driver. The driver propagating at a subluminal group velocity excites the plasma wakefield with the same phase velocity. However, due to the positive density gradient, the wake phase velocity steadily increases behind the driver.

Laser-driven vacuum breakdown waves.

It is demonstrated by three-dimensional quantum electrodynamics - particle-in-cell (QED-PIC) simulations that vacuum breakdown wave in the form of QED cascade front can propagate in an extremely intense plane electromagnetic wave. The result disproves the statement that the self-sustained cascading is not possible in a plane wave configuration. In the simulations the cascade is initiated during laser-foil interaction in the light sail regime.

Probing non-perturbative QED with electron-laser collisions.

The vast majority of QED results are obtained in relatively weak fields and so in the framework of perturbation theory. However, forthcoming laser facilities providing extremely high fields can be used to enter not-yet-studied regimes. Here, a scheme is proposed that might be used to reach a supercritical regime of radiation reaction or even the fully non-perturbative regime of quantum electrodynamics.

Field-reversed bubble in deep plasma channels for high-quality electron acceleration.

We study hollow plasma channels with smooth boundaries for laser-driven electron acceleration in the bubble regime. Contrary to the uniform plasma case, the laser forms no optical shock and no etching at the front. This increases the effective bubble phase velocity and energy gain.

Radiation-reaction trapping of electrons in extreme laser fields.

A radiation-reaction trapping (RRT) of electrons is revealed in the near-QED regime of laser-plasma interaction. Electrons quivering in laser pulse experience radiation reaction (RR) recoil force by radiating photons. When the laser field reaches the threshold, the RR force becomes significant enough to compensate for the expelling laser ponderomotive force.

Two-screen single-shot electron spectrometer for laser wakefield accelerated electron beams.

The laser wakefield acceleration electron beams can essentially deviate from the axis of the system, which distinguishes them greatly from beams of conventional accelerators. In case of energy measurements by means of a permanent-magnet electron spectrometer, the deviation angle can affect accuracy, especially for high energies. A two-screen single-shot electron spectrometer that correctly allows for variations of the angle of entry is considered.

Laser field absorption in self-generated electron-positron pair plasma.

Recently, much attention has been attracted to the problem of limitations on the attainable intensity of high power lasers [A. M. Fedotov et al.

Electron self-injection in multidimensional relativistic-plasma wake fields.

We present an analytical model for electron self-injection in a nonlinear, multidimensional plasma wave excited by a short laser pulse in the bubble regime or by a short electron beam in the blowout regime. In these regimes, which are typical for electron acceleration, the laser radiation pressure or the electron beam charge pushes out background plasma electrons forming a plasma cavity--bubble--with a huge ion charge. The plasma electrons can be trapped in the bubble and accelerated by the plasma wakefields up to very high energies.

Carrier-envelope phase effects in plasma-based electron acceleration with few-cycle laser pulses.

Carrier-envelope phase effects during the interaction of relativistically intense few-cycle laser pulses with a plasma are studied in the ''bubble'' regime when an electron cavity (bubble) is formed behind the pulse. We show that for few-cycle laser pulses the cavity shape becomes asymmetric and depends strongly on the carrier-envelope phase. The carrier-envelope phase varies when the laser pulse propagates in plasma, which causes transverse oscillations of the cavity.

Control of laser-wakefield acceleration by the plasma-density profile.

We show that both the maximum energy gain and the accelerated beam quality can be efficiently controlled by the plasma-density profile. Choosing a proper density gradient one can uplift the dephasing limitation and keep the phase synchronism between the bunch of relativistic particles and the plasma wave over extended distances. Putting electrons into the n th wake period behind the driving laser pulse, the maximum energy gain is increased by the factor, which is proportional to n, over that in the case of uniform plasma.

Radiation emission by extreme relativistic electrons and pair production by hard photons in a strong plasma wakefield.

The radiation spectrum of extreme relativistic electrons and the probability of electron-positron pair production by energetic photons in a strong plasma wakefield are derived in the framework of a semiclassical approach. It is shown that the radiation losses of a relativistic electron in the plasma wakefield scale proportionally to epsilon2/3 in the quantum limit when the energy of the radiated photon becomes close to the electron energy epsilon . The quantum effects will play a key role in future plasma-based accelerators operating at ultrahigh electron energy.

Collisional versus collisionless resonant and autoresonant heating in laser-cluster interaction.

When a hot cluster expands, a transient matching between the plasma frequency and the laser frequency has been predicted, observed, and analyzed recently. The associate energy transfer to the electrons has been described as an enhanced collisional absorption. However, for hot plasmas the collision frequency is small and a collisionless resonant heating is more efficient.

X-ray generation in strongly nonlinear plasma waves.

We show that a laser wake field in the "bubble" regime [Appl. Phys. B 74, 355 (2002)]], works as a compact high-brightness source of x-rays.

Self-compression of laser pulses in plasma.

We study self-compression of weakly relativistically intense laser pulses in subcritical plasmas using one- (1D) and three-dimensional (3D) direct particle-in-cell (PIC) simulations. The self-compression works in the density window from 1/4 critical to slightly below critical density, where the Raman instability is prohibited. An analytical model is developed to describe the self-compression.