Konstantin Y. Platonov

Efficient generation of fast ions from surface modulated nanostructure targets irradiated by high intensity short-pulse lasers

It’s shown that the imposition of sub-laser wavelength relief structures on the surface of mass-limited-targets results into several folds higher short-pulse laser absorption, and consequently the efficient generation of fast ions. The optimum relief parameters for enhanced short-pulse laser absorption and higher ion acceleration are estimated numerically by particle-in-cell simulations and then corroborated by analytical scalings. The stability of the pre-imposed surface modulation during the laser pulse foil interaction is also examined.

Laser proton acceleration in a water spray target

Studies of interaction of a cloud of submicrometer water droplets with ultrashort (40fs) and intense (∼2×1019W∕cm2) laser pulses demonstrate an efficient acceleration of protons and oxygen ions. Due to a high ratio of the volume to the enveloping surface of a single droplet and a large number of droplets in a focal volume, efficient laser pulse absorption is enabled, which provides high electron temperatures and ion acceleration to high energies. The generation of ions with energies more than 1MeV per nucleon is demonstrated. The observed quasi-monoenergetic feature in the proton spectrum is discussed with the thermal expansion–Coulomb explosion model and numerical simulations.

Sub-structure of laser generated harmonics reveals plasma dynamics of a relativistically oscillating mirror

Theoretical and experimental investigations of the dynamics of a relativistically oscillating plasma slab reveal spectral line splitting in laser driven harmonic spectra, leading to double harmonic series. Both series are well characterized with harmonics arising by two fundamental frequencies. While a relativistic oscillation of the critical density drives the harmonic emission, the splitting is a result of an additional acceleration during the laser pulse duration. In comparison with the oscillatory movement, this acceleration is rather weak and can be described by a plasma shock wave driven by the pressure of light. We introduce particle in cell simulations and an analytical model explaining the harmonic line splitting. The derived analytical formula gives direct access between the splitting in the harmonic spectrum and the acceleration of the plasma surface.

Interaction of intense intersecting laser beams with electron bunch

In recent years new high-intensity subpicosecond lasers allowed to investigate property of matter in ultrahigh electromagnetic fields. In this work the electron motion equations in field of three orthogonal standing waves is being solved. This solution was obtained by method of average Hamiltonian, when the electron velocity in laser field vE equals eE0/m(omega) is less than light velocity c ((omega) - laser frequency).

Effective generation of fast particles and short wavelength radiation from nano-structure targets irradiated by relativistic intensity laser pulse

In the present paper it is offered to significantly increase target absorption and to optimize parameters of a relief and basic part of a target so that an absorbed energy is transferred to an accelerated particles and reflected (transmitted) energy is radiated as attosecond pulses. The choice of optimum characteristics of a target is made by means of analytical and multi-dimensional numerical modeling of a target set with characteristics near to optimum values. It is shown, that at reflection from a target the laser wave of relativistic intensity is effectively converted in sequence of electromagnetic pulses of tens nanometer length, the following one after another through the period of an initial laser wave. Dependence of its parameters on angle of incidence and laser intensity is investigated.

Generation of K{sub {alpha}} radiation by high-efficiency laser targets

The intensity of Kα radiation emanating from transversely limited thin laser targets with a periodic relief superposed onto its front side was calculated. The relief parameters and the geometrical target dimensions were optimised with the help of an analytic model. The optimal target was shown to possess a nearly 100% absorption coefficient for laser radiation and a high (up to 10-3) coefficient of laser radiation conversion to the X-ray Kα radiation.

Effect of a laser prepulse on ion acceleration when an ultra-intense laser pulse interacts with a foil target

Upon the interaction of an ultra intense laser pulse with a solid target, generated fast electrons can produce MeV ions from laser plasmas. These fast ions can be used in different applications ranging from ion implantation to nuclear reaction stimulation. The most important point is the efficiency of this fast ion production. We analyze--with help of an analytical model and PIC code simulations--the different acceleration mechanisms and compare the efficiency of electrostatic ion acceleration, at the front and rear of a foil target, the ponderomotive mechanism and acceleration by the shock wave in detail. The optimal plasma density distribution, shaped by laser prepulse, is found.

Scattered light diagnostic of over-dense plasma cavity at ultraintense laser pulse interaction with solid target

The light scattered backward from a target illuminated by ultra intense laser pulses carries important information about the nonlinear laser plasma interaction. We analyze the possibility of using this information with the help of developed analytical model and PIC simulations. The spectrum of scattered light is shown to be shifted, to be broadened and to be modulated, in comparison with the initial laser spectrum.

Backscattering of ultrashort high-intensity laser pulses from solid targets at oblique incidence

Back reflection of short, intense laser pulses at oblique incidence on solid targets is explained with a model where a periodic electron density modulation acts as a diffraction grating. The pump and reflected electromagnetic waves drive through the ponderomotive force the grating and the overall system becomes parametrically unstable. The basic equations governing this system are given. A linearized stability analysis yields the instability growth rate for a homogeneous plasma and the convective gain coefficients for the inhomogeneous case. The results support the feasibility of the suggested mechanism. An absolute instability is predicted to set on at a typical threshold intensity 1016 W/cm2, laser pulse length 100 fs, and spot size 30 micrometers . The instability is shown to saturate at a level of a few percent, because the higher harmonics in the electron density modulation turn the diffraction more diffuse thus reducing both the sustaining ponderomotive force and the back reflection coefficient.

Laser-excited gamma source with high spectral brightness

This paper considers various channels of (gamma) -quantum generation via an ultra-short high-power laser pulse interaction with different targets. We analyze the possibilities to create a pulsed (gamma) -radiation source using laser triggering of some nuclear reactions and isomer targets. It is shown that 0.2 MeV monochromatic short pulse of (gamma) -radiation can be obtained with pulse energy sub- mJ level from isomer atoms localized in a magnetic trap. For nuclear reaction channel in light-atom materials, it is shown that 100-TW laser pulse gives rise to formation of about 106 (gamma) -photons near 5 MeV energy.