Design of modular multi-channel electron spectrometers for application in laser matter interaction experiments at Prague Asterix Laser System.

This paper describes design, development, and implementation of a multi-channel magnetic electron spectrometer for the application in laser-plasma interaction experiments carried out at the Prague Asterix Laser System. Modular design of the spectrometer allows the setup in variable configurations to evaluate the angular distribution of hot electron emission. The angular array configuration of the electron spectrometers consists of 16 channels mounted around the target. The modules incorporate a plastic electron collimator designed to suppress the secondary radiation by absorbing the wide angle scattered electrons and photons inside the collimator. The compact model of the spectrometer measures electron energies in the range from 50 keV to 1.5MeV using ferrite magnets and from 250 keV to 5MeV using stronger neodymium magnets. An extended model of the spectrometer increases the measured energy range up to 21MeV or 35MeV using ferrite or neodymium magnets, respectively. Position to energy calibration was obtained using the particle tracking simulations. The experimental results show the measured angularly resolved electron energy distribution functions from interaction with solid targets. The angular distribution of hot electron temperature, the total flux, and the maximum electron energy show a directional dependence. The measured values of these quantities increase toward the target normal. For a copper target, the average amount of measured electron flux is 1.36 × 1011, which corresponds to the total charge of about 21 nC.

Magnetized plasma implosion in a snail target driven by a moderate-intensity laser pulse.

Optical generation of compact magnetized plasma structures is studied in the moderate intensity domain. A sub-ns laser beam irradiated snail-shaped targets with the intensity of about 1016 W/cm2. With a neat optical diagnostics, a sub-megagauss magnetized plasmoid is traced inside the target. On the observed hydrodynamic time scale, the hot plasma formation achieves a theta-pinch-like density and magnetic field distribution, which implodes into the target interior. This simple and elegant plasma magnetization scheme in the moderate-intensity domain is of particular interest for fundamental astrophysical-related studies and for development of future technologies.

Synchronizing single-shot high-energy iodine photodissociation laser PALS and high-repetition-rate femtosecond Ti:sapphire laser system.

A system of precise pulse synchronization between a single-shot large-scale laser exploiting an acousto-optical modulator and a femtosecond high repetition rate laser is reported in this article. This opto-electronical system has been developed for synchronization of the sub-nanosecond kJ-class iodine photodissociation laser system (Prague Asterix Laser System-PALS) with the femtosecond 25-TW Ti:sapphire (Ti:Sa) laser operating at a repetition rate 1 kHz or 10 Hz depending on the required energy level of output pulses. At 1 kHz synchronization regime, a single femtosecond pulse of duration about 45 fs and a small energy less than 1 mJ are exploited as a probe beam for irradiation of a three-frame interferometer, while at 10 Hz repetition rate a single femtosecond pulse with higher energy about 7-10 mJ is exploited as a probe beam for irradiation of a two-channel polaro-interferometer. The synchronization accuracy ±100 ps between the PALS and the Ti:Sa laser pulses has been achieved in both regimes of synchronization. The femtosecond interferograms of laser-produced plasmas obtained by the three-frame interferometer and the femtosecond polarimetric images obtained by the two-frame polaro-interferometer confirm the full usefulness and correct functionality of the proposed method of synchronization.