Non-adiabatic cluster expansion after ultrashort laser interaction

AbstractWe used X-ray spectroscopy as a diagnostic tool for investigating the properties of laser-cluster interactions at the stage in which non-adiabatic cluster expansion takes place and a quasi-homogeneous plasma is produced. The experiment was carried out with a 10 TW, 65 fs Ti:Sa laser focused on CO2 cluster jets. The effect of different laser-pulse contrast ratios and cluster concentrations was investigated. The X-ray emission associated to the Rydberg transitions allowed us to retrieve, through the density and temperature of the emitting plasma, the time after the beginning of the interaction at which the emission occurred. The comparison of this value with the estimated time for the "homogeneous" plasma formation shows that the degree of adiabaticity depends on both the cluster concentration and the pulse contrast. Interferometric measurements support the X-ray data concerning the plasma electron density

Discharge plasma formation in square capillary with gas supply channels

A comprehensive model of processes in a discharge capillary is required in order to obtain nominal parameters of a preformed plasma channel suitable for the laser wake-field acceleration. We present three-dimensional magnetohydrodynamics simulations of a hydrogen gas filling process and discharge plasma formation in a short square shaped capillary with gas supply channels. Time evolution of the gas pressure and the plasma density in the capillary channel for a chosen discharge current profile is analyzed. Performed simulations provide distributions of the electric current, the magnetic field, and the electron density along the whole channel, taking into account gas supply areas as well as areas outside of the capillary. Obtained results show that the presence of gas supplies leads to the inhomogeneous plasma density distribution along the capillary channel which has to be taken into account for generating an optimal laser-driven electron beam

Discharge plasma formation in square capillary with gas supply channels

A comprehensive model of processes in a discharge capillary is required in order to obtain nominal parameters of a preformed plasma channel suitable for the laser wake-field acceleration. We present three-dimensional magnetohydrodynamics simulations of a hydrogen gas filling process and discharge plasma formation in a short square shaped capillary with gas supply channels. Time evolution of the gas pressure and the plasma density in the capillary channel for a chosen discharge current profile is analyzed. Performed simulations provide distributions of the electric current, the magnetic field, and the electron density along the whole channel, taking into account gas supply areas as well as areas outside of the capillary. Obtained results show that the presence of gas supplies leads to the inhomogeneous plasma density distribution along the capillary channel which has to be taken into account for generating an optimal laser-driven electron beam