Multiterawatt Laser Pulses Research Articles

Numerical analysis of 10's femtosecond relativistic electron beam generation using single 12 TW50 fs laser pulse

Particle-in-cell two-dimensional (PIC-2D) simulations have been performed to verify the trapping of plasma electrons in the wake of ultrashort, multi-terawatt laser pulse as it propagates through underdense uniform plasma. It is supposed that the wake wavebreaking is the reason for the beam generation. This mechanism may lead to a compact ultrashort-pulse relativistic electron accelerator/injector (we call it laser–plasma linac). For a laser pulse with a duration of 50 fs and a peak power of 12 TW propagating through plasma, the simulation results show the generation of electron beam from the self-trapped plasma electrons with maximum energy >25 MeV and pulse duration of about 12 fs at FWHM. The two-dimensional effect of the plasma wave and the phase space of accelerated electrons are discussed. The present numerical results are relevant to the laser–plasma acceleration experiments that use the 12 TW 50 fs laser system at the Nuclear Engineering Research Laboratory (NERL), University of Tokyo.

Relativistic second-harmonic generation and conversion in a weakly magnetized plasma

Relativistic second-harmonic generation with ultrahigh intensity laser pulses in a weakly magnetized plasma is analyzed. Both ordinary mode conversion to second-harmonic extraordinary mode and extraordinary mode conversion to second-harmonic extraordinary mode are considered. Extraordinary mode conversion turns out to be more efficient, and a new frequency doubling scheme based on a tapered magnetic wiggler is identified, described, and analyzed. The important issues of phase matching, pump depletion, and relativistic tapering are addressed and solved. Both permanent magnet and laser-driven wigglers are considered. The interaction of multi-terawatt laser pulses with a magnetized plasma appears to provide an efficient scheme to generate short wavelengths.

Quantum Effects on the Motion of Charged Particles near the Neutral Surface of an Ultrastrong Magnetic Field

The problem of quantum motion of charged particles in a magnetic field is extended to the case where the magnetic field has a neutral surface. This situation may occur in ultrahigh magnetic fields generated by multi-terawatt laser pulses interacting with a plasma of ~10–100 eV. Far from the neutral surface the drift approximation holds for the classical motion and the Landau description holds for the quantum motion. Near the neutral layer at a classical distance less than the Larmor radius the particle motion is nonadiabatic. Here the quantum motion is described by a Schrödinger equation and new quantum levels for the particle transverse energy are found, with a separation that depends on the particle momentum along the neutral surface.

Hard X-ray radiation and fast particle generation using multiterawatt laser pulses

Hard X-ray radiation and fast particle generation using multiterawatt laser pulses

Generatsiya zhestkogo rengenovskogo izlucheniya i bystrykh chastits mul'titeravattnymi lazernymi impul'sami

Генерация жесткого ренгеновского излучения и быстрых частиц мультитераваттными лазерными импульсами, Андреев А.А., Яшин В.Е., Чарухчев А.В.

Production of direct fusion neutrons during ultra-intense laser-plasma interaction

The plasma response to a picosecond multi-terawatt laser pulse is characterized by several distinctly different time scales. In the present report we consider the plasma's evolution on the slow time scale typical for excitations of the ionic component. A relativistically strong laser pulse (-) is shown to drive, under proper conditions, mega-ampere ion currents with a typical ion energy of 50-150 keV, which covers the region of the resonance peak in the cross section of D-T fusion and, hence, provides an opportunity to initiate nuclear reactions directly in the laser focus.

Compact FROG system useful for measurement of multiterawatt laser pulses

We present a compact FROG system for determination of both pulse shape and phase of sub-picosecond pulses in a single-shot measurement. The system utilizes third-order auto-correlation due to the induced optical Kerr effect in heavy flint glass (SF6). The optical layout allows to use single Calcite wedges as high-contrast polarizers. Instead of using a separate spectrgraph, we incorporated a grating and appropriate imaging optics directly into the optical scheme. The FROG system has proven to be a convenient measurement tool to optimally align the grating compressor of CPA laser systems.

Challenge to a tabletop high-energy laser wake-field accelerator

Recently there has been a great interest in laser–plasma accelerators as possible next generation particle accelerators because of their potential for ultrahigh accelerating gradients and a compact size compared with conventional accelerators. Particle acceleration occurs through interaction with large-amplitude plasma waves driven by an intense short laser pulse, known as a laser wake-field acceleration mechanism. Our recent experiments have demonstrated ultrahigh-gradient electron acceleration in the accelerating gradient of the order of 30 GeV/m excited by a multiterawatt laser pulse to obtain 18 MeV electrons. The current research is in progress to achieve a high-energy particle acceleration to the energies more than a GeV in a tabletop scale by the use of a 100 fs, 2 TW tabletop-terawatt laser system.

Experimental observations and simulations on relativistic self-guiding of an ultra-intense laser pulse in underdense plasmas

The experimental images of the sidescattered light from a plasma, created by the multiterawatt laser pulse propagating in a hydrogen gas jet, exhibit clear dependence on both gas jet pressure and laser power. Two- and three-dimensional simulations of wave propagation, in presence of the relativistic electron mass increase and the ponderomotive expel of electrons, have been performed to reproduce the Thomson radiation from the plasma electrons. They show electron cavitation induced by the beam focusing, self-focusing, self-guiding, smoothing of the beam nonuniformities and, at larger power, beam filamentation. A bremsstrahlung model with account of the ionization, heating, expansion, and recombination dynamics of the gas, provides the plasma emission background. Both Thomson emission and bremsstrahlung are required to recover the experimental emission patterns. Among the interpretations, a scenario of laser self-guiding over five Rayleigh lengths can be found for 10 TW laser power and 5×1018 cm−3 electron density, which surprisingly disappears at larger powers and densities.

RELATIVISTIC SELF-FOCUSING OF AN ULTRA-INTENSE LASER PULSE IN A PLASMA

New compact multiterawatt lasers allow us to study the relativistic regime of laserplasma interaction. The propagation of a multiterawatt subpicosecond laser pulse in a plasma has been investigated theoretically and experimentally. A 10 TW laser pulse at a 1064 nm wavelength has been focused in a hydrogen gas jet. Thomson scattering observations show that a relativistic self-focusing and channeling occur when the laser power exceeds a critical value predicted by theory. The amount of enhancement in self-focused intensity exceeds one order of magnitude. The laser pulse propagates through the plasma over a distance much larger than the Rayleigh length determined by vacuum diffraction.

Experimental demonstration of relativistic self-channeling of a multiterawatt laser pulse in an underdense plasma.

Experimental demonstration of relativistic self-channeling of a multiterawatt laser pulse in an underdense plasma.

Focusing behavior of multiterawatt laser pulse in a H 2 gas jet

Reported is on the propagation and on the focusing of a 1064 nm 1 ps multiterawatt laser pulse in a H 2 gas jet. The focusing is diagnosed by viewing the second harmonic emission. It is shown that high intensities can be maintained in the presence of a high density plasma.