Quasimonoenergetic deuteron bursts produced by ultraintense laser pulses

We report on the generation and laser acceleration of bunches of energetic deuterons with a small energy spread at about 2 MeV. This quasimonoenergetic peak within the ion energy spectrum was observed when heavy-water microdroplets were irradiated with ultrashort laser pulses of about 40 fs duration and high (10(-8)) temporal contrast, at an intensity of 10(19) W/cm(2). The results can be explained by a simple physical model related to spatial separation of two ion species within a finite-volume target. The production of quasimonoenergetic ions is a long-standing goal in laser-particle acceleration; it could have diverse applications such as in medicine or in the development of future compact ion accelerators.     

Nuclear reactions triggered by laser-accelerated high-energy ions

A technique is suggested for triggering nuclear reactions by accelerating ions with a powerful ultrashort laser pulse in a plasma. The underlying idea of the suggested compact “reactor” is utilization of high-energy ions accelerated by the charge-separation electrostatic field in the direction perpendicular to the laser beam axis in a gas-filled capillary. Accelerated ions with energies of several MeV penetrating the target from the inside surface of a channel give rise to nuclear reactions which can be used to create a compact source of fast neutrons and neutrons of intermediate energies for generating various (short-and long-lived, light and heavy) isotopes, for generating gamma radiation over a broad energy range, for making sources of light ion and induced radioactivity. The yield of the corresponding nuclear reactions as a function of the laser beam parameters has been investigated. The suggested technique for triggering nuclear reactions provides a practical tool for studies of nuclear transformation on the pico-and nanosecond scales, which cannot be achieved using other methods. Zh. éksp. Teor. Fiz. 115, 2080–2090 (June 1999)     

Effect of pressure relaxation during the laser heating and electron–ion relaxation stages

The multi-phase equation of state by Bushman et al. (Sov. Tech. Rev. 5:1–44, 2008) is modified to describe states with different electron and ion temperatures and it is applied to the non-equilibrium evolution of an aluminum sample heated by a subpicosecond laser pulse. The sample evolution is described by the two-temperature model for the electron and ion temperatures, while the pressure and density are described by a simplified relaxation equation. The pressure relaxation in the heating stage reduces the binding energy and facilitates the electron-driven ablation. The model is applied to estimate the ablation depth of an Al target irradiated by a subpicosecond laser pulse. It improves the agreement with the experimental data and provides a new explanation of the ablation process.     

Half-Integer Harmonics Generation in Laser-Produced Plasma

Half integer (3/2ω₀, 1/2ω₀) harmonics generation under oblique incidence of the pump-wave on the spatially inhomogeneous plasma is theoretically investigated. Harmonics generation is connected with the two-plasmon convective instability excitation near the quarter-critical density. Harmonics spectra and intensities depend essentially on the pump wave polarization. In particular, significant harmonics spectra broadening arises under the p-polarized pump wave.     

Stability and bistability of stationary states in four-wave interaction in a photorefractive medium

The stability of stationary states is investigated analytically and numerically for various four-wave mixing schemes in a photorefractive medium with nonlocal nonlinear response when recorded with a translucent grating. Bistability is indicated for a number of four-wave-mixing schemes and the conditions for its existence are indicated.Quantum-Radiophysics Division, Plasma-Phenomena-Theory Sector, Lebedev Physics Institute. Translated from Preprint No. 138 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989.