Semiconductor Detectors for Observation of Multi-MeV Protons and Ions Produced by Lasers

The application of time-of-flight Faraday cups and SiC detectors for the measurement of currents of fast ions emitted by laser-produced plasmas is reported. Presented analysis of signals of ion detectors reflects the design and construction of the detector used. A similarity relation between output signals of ion collectors and semiconductor detectors is established. Optimization of the diagnostic system is discussed with respect to the emission time of electromagnetic pulses interfering with signals induced by the fastest ions accelerated up to velocities of 107 m/s. The experimental campaign on laser-driven ion acceleration was performed at the PALS facility in Prague

Two-dimensional model of thermal smoothing of laser imprint in a double-pulse plasma

The laser prepulse effect on the thermal smoothing of nonuniformities of target illumination is studied by means of a two-dimensional Lagrangian hydrodynamics simulation, based on the parameters of a real experiment. A substantial smoothing effect is demonstrated for the case of an optimum delay between the prepulse and the main heating laser pulse. The enhancement of the thermal smoothing effect by the laser prepulse is caused by the formation of a long hot layer between the region of laser absorption and the ablation surface. A comparison with experimental results is presented

Controllable Laser Ion Acceleration

In this paper a future laser ion accelerator is discussed to make the laser-based ion accelerator compact and controllable. Especially a collimation device is focused in this paper. The future laser ion accelerator should have an ion source, ion collimators, ion beam bunchers, and ion post acceleration devices [Laser Therapy 22, 103(2013)]: the ion particle energy and the ion energy spectrum are controlled to meet requirements for a future compact laser ion accelerator for ion cancer therapy or for other purposes. The energy efficiency from the laser to ions is improved by using a solid target with a fine sub-wavelength structure or a near-critical density gas plasma. The ion beam collimation is performed by holes behind the solid target or a multi-layered solid target. The control of the ion energy spectrum and the ion particle energy, and the ion beam bunching would be successfully realized by a multistage laser-target interaction

Numerical and experimental studies of K-α\alpha emission from femtosecond-laser-irradiated foil targets

We present here our numerical model of K-$\alpha$ emission from ultrashort pulse laser irradiated foil targets for the experimental conditions [1]. In our simulations, we use initial plasma density profile calculated by hydrodynamic code for the ASE prepulse target interaction. This profile contains a long subcritical part and we show how this subcritical part may influences fast electron generation and K-$\alpha$ emission from the target

Tungsten modification induced by femtosecond laser with 1014 W/cm2 intensity in vacuum

Irradiation of refractory metals including tungsten (W) by high intensity laser radiation possesses fundamental as well as applied significance. Due to extraordinary characteristics, tungsten is nowadays an interesting metal which can be used in wide range of applications, from electronic to nuclear field. In the latter area, it is well known that tungsten can be used as plasma-facing material in fusion device/reactor [1] where high fluxes are present. Behavior/modification of tungsten surface under the action of high intensity laser radiation is scarce in literature and the goal of this research is focused in that direction. Tungsten modification in this study was done by pulsed, femtosecond laser [2,3] with the following parameters: output pulse energy up to 12 mJ; emission wavelength 800 nm; laser pulse duration 60 fs; repetition rate up to 10 Hz; fluence and intensity 16.2 J/cm2 and 2.7 1014 W/cm2 ,respectively (focusing regime), etc. Irradiation was carried out in vacuum, helium and air ambience. Generally, surface modification of the tungsten depends on the laser output parameters - pulse energy density (fluence), intensity, wavelength, laser pulse duration, number of accumulated laser pulses, etc., as well as the sample characteristics, for example absorptivity, and used environmental conditions (e.g. vacuum or gas (helium, air, etc.)). Surface changes and phenomena at W-target, in vacuum ambience, can be summarized as follows: (i) crater shaped damages with depth increasing with higher number of accumulated laser pulses; (ii) formation of solid droplets at near and further periphery; (iii) vast rim surrounding craters, and (iv) appearance of intensive plasma.VI International School and Conference on Photonics and COST actions: MP1406 and MP1402 : PHOTONICA2017 : August 23 - September 1, 2017; Belgrade