L. Labate

Fast-electron transport in cylindrically laser-compressed matter

Experimental and theoretical results of relativistic electron transport in cylindrically compressed matter are presented. This experiment, which is a part of the HiPER roadmap, was achieved on the VULCAN laser facility (UK) using four long pulses beams (~4 × 50 J, 1 ns, at 0.53 µm) to compress a hollow plastic cylinder filled with plastic foam of three different densities (0.1, 0.3 and 1 g cm−3). 2D simulations predict a density of 2–5 g cm−3 and a plasma temperature up to 100 eV at maximum compression. A short pulse (10 ps, 160 J) beam generated fast electrons that propagate through the compressed matter by irradiating a nickel foil at an intensity of 5 × 1018 W cm−2. X-ray spectrometer and imagers were implemented in order to estimate the compressed plasma conditions and to infer the hot electron characteristics. Results are discussed and compared with simulations.

Proton radiography of laser-driven imploding target in cylindrical geometry

An experiment was done at the Rutherford Appleton Laboratory (Vulcan laser petawatt laser) to study fast electron propagation in cylindrically compressed targets, a subject of interest for fast ignition. This was performed in the framework of the experimental road map of HiPER (the European high power laser energy research facility project). In the experiment, protons accelerated by a picosecond-laser pulse were used to radiograph a 220u2002μm diameter cylinder (20u2002μm wall, filled with low density foam), imploded with ∼200u2002J of green laser light in four symmetrically incident beams of pulse length 1 ns. Point projection proton backlighting was used to get the compression history and the stagnation time. Results are also compared to those from hard x-ray radiography. Detailed comparison with two-dimensional numerical hydrosimulations has been done using a Monte Carlo code adapted to describe multiple scattering and plasma effects. Finally we develop a simple analytical model to estimate the performance of prot...

The HiPER project for inertial confinement fusion and some experimental results on advanced ignition schemes

This paper presents the goals and some of the results of experiments conducted within the Working Package 10 (Fusion Experimental Programme) of the HiPER Project. These experiments concern the study of the physics connected to advanced ignition schemes, i.e. the fast ignition and the shock ignition approaches to inertial fusion. Such schemes are aimed at achieving a higher gain, as compared with the classical approach which is used in NIF, as required for future reactors, and make fusion possible with smaller facilities.In particular, a series of experiments related to fast ignition were performed at the RAL (UK) and LULI (France) Laboratories and studied the propagation of fast electrons (created by a short-pulse ultra-high-intensity beam) in compressed matter, created either by cylindrical implosions or by compression of planar targets by (planar) laser-driven shock waves. A more recent experiment was performed at PALS and investigated the laser?plasma coupling in the 1016?W?cm?2 intensity regime of interest for shock ignition.

Laser-driven cylindrical compression of targets for fast electron transport study in warm and dense plasmas

Fast ignition requires a precise knowledge of fast electron propagation in a dense hydrogen plasma. In this context, a dedicated HiPER (High Power laser Energy Research) experiment was performed on the VULCAN laser facility where the propagation of relativistic electron beams through cylindrically compressed plastic targets was studied. In this paper, we characterize the plasma parameters such as temperature and density during the compression of cylindrical polyimide shells filled with CH foams at three different initial densities. X-ray and proton radiography were used to measure the cylinder radius at different stages of the compression. By comparing both diagnostics results with 2D hydrodynamic simulations, we could infer densities from 2 to 11 g/cm3 and temperatures from 30 to 120 eV at maximum compression at the center of targets. According to the initial foam density, kinetic, coupled (sometimes degenerated) plasmas were obtained. The temporal and spatial evolution of the resulting areal densities a...

Proton radiography of cylindrical laser-driven implosions

A recent experiment was performed at the Rutherford Appleton Laboratory (UK) to study fast electron propagation in cylindrically compressed targets, a subject of interest for fast ignition. In this experiment, protons accelerated by a picosecond laser pulse have been used to radiograph a 220 µm diameter cylinder (10 µm wall filled with 0.1 g/cc foam), imploded with _ 200 J of green laser light in 4 symmetrically incident beams of wavelength and pulse length 1 ns. Point projection proton backlighting was used to measure the compression degree as well as the stagnation time. Results were also compared to those from a hard X-ray radiography diagnostics. Finally, Monte Carlo simulations of proton propagation in the cold and in the compressed targets allowed a detailed comparison with 2D numerical hydro simulations.

Experimental results performed in the framework of the HIPER European Project

This paper presents the goals and some of the results of experiments conducted within the Working Package 10 (Fusion Experimental Programme) of the HiPER Project. These experiments concern the study of the physics connected to Advanced Ignition Schemes, i.e. the Fast Ignition and the Shock Ignition Approaches to Inertial Fusion. Such schemes are aimed at achieving a higher gain, as compared to the classical approach which is used in NIF, as required for future reactors, and making fusion possible with smaller facilities. In particular, a series of experiments related to Fast Ignition were performed at the RAL (UK) and LULI (France) Laboratories and were addressed to study the propagation of fast electrons (created by a short-pulse ultra-high-intensity beam) in compressed matter, created either by cylindrical implosions or by compression of planar targets by (planar) laser-driven shock waves. A more recent experiment was performed at PALS and investigated the laser-plasma coupling in the 1016 W/cm2 intensity regime of interest for Shock Ignition.

Can proton radiography be used to image imploding target in ICF experiments

Generation of high intensity and well collimated multi energetic proton beams from laser-matter interaction extend the possibility to use protons as a diagnostic to image imploding target in Inertial Confinement Fusion experiments. An experiment was done at the Rutherford Appleton Laboratory (Vulcan Laser Petawatt laser) to study fast electron propagation in cylindrically compressed targets, a subject of interest for fast ignition. This was performed in the framework of the experimental road map of HiPER (the European High Power laser Energy Research facility Project). In the experiment, protons accelerated by a ps-laser pulse were used to radiograph a 220 m diameter cylinder (20 m wall, filled with low density foam), imploded with 200 J of green laser light in 4 symmetrically incident beams of pulse length 1 ns. Point projection proton backlighting was used to get the compression history and the stagnation time. Detailed comparison with 2D numerical hydro simulations has been done using a Monte Carlo code adapted to describe multiple scattering and plasma effects and with those from hard X-ray radiography. These analysis shows that due to the very large mass densities reached during implosion processes, protons traveling through the target undergo a very large number of collisions which deviate protons from their original trajectory reducing proton radiography resolution. Here we present a simple analytical model to study the proton radiography diagnostic performance as a function of the main experimental parameters such as proton beam energy and target areal density. This approach leads to define two different criteria for PR resolution (called strong and weak condition) describing different experimental conditions. Finally numerical simulations using both hydrodynamic and Monte Carlo codes are presented to validate analytical predictions.

Proton radiography of a cylindrical laser-driven implosion

A recent experiment was performed at the Rutherford Appleton Laboratory (UK) to study fast electron propagation in cylindrically compressed targets, a subject of interest for fast ignition. In this experiment, protons accelerated by a picosecond laser pulse have been used to radiograph a 220 µm diameter cylinder (10 µm wall filled with 0.1 g/cc foam), imploded with _ 200 J of green laser light in 4 symmetrically incident beams of wavelength and pulse length 1 ns. Point projection proton backlighting was used to measure the compression degree as well as the stagnation time. Results were also compared to those from a hard X-ray radiography diagnostics. Finally, Monte Carlo simulations of proton propagation in the cold and in the compressed targets allowed a detailed comparison with 2D numerical hydro simulations.