Multi-petawatt Laser Research Articles

Extreme Light Infrastructure – Nuclear Physics

The Extreme Light Infrastructure (ELI) is an ESFRI-listed distributed facility that entered the implementation phase. The Romanian pillar will focus on the field of nuclear physics research, performed with the help of an ultra-short-pulse, multi-petawatt scale laser system and a brilliant, tuneable and highly collimated gamma beam system. ELI-Nuclear Physics, an open-access facility, shall become operational and receive the first visiting research teams in 2017. We report herein on the status of the implementation and some of the research topics proposed for ELI-NP.

Heat wave fast ignition in inertial confinement energy

AbstractAn accelerated micro-foil is used to ignite a pre-compressed cylindrical shell containing deuterium–tritium fuel. The well-known shock wave ignition criterion and a novel criterion based on heat wave ignition are developed in this work. It is shown that for heat ignition very high impact velocities are required. It is suggested that a multi-petawatt laser can accelerate a micro-foil to relativistic velocities in a very short time duration (˜picosecond) of the laser pulse. The cylindrical geometry suggested here for the fast ignition approach has the advantage of geometrically separating the nanosecond lasers that compress the target from the picosecond laser that accelerates the foil. The present model suggests that nuclear fusion by micro-foil impact ignition could be attained with currently existing technology.

Overview of PETAL, the multi-Petawatt project in the LMJ facility

A multi-Petawatt high-energy laser PETAL coupled to the Ligne d’Int´ Laser (LIL) is under construction in the Aquitaine Region in France. This Petawatt laser will be dedicated to academic experiments in the fields of high energy density physics and ultra high intensity. Nd : glass laser chain coupled with the chirped pulse amplification (CPA technique allows delivery of high energy. Optical parametric CPA for pre-amplification and a new compression scheme will be implemented. PETAL is designed to deliver 3.6 kJ of energy in 500 fs on a target corresponding to 7.2 PW. The PETAL beam linked to the up to 60 kJ ns UV beams from the LIL will present new scientific research opportunities. (Some figures in this article are in colour only in the electronic version)

100-GeV large scale laser plasma electron acceleration by a multi-PW laser

We present three possible design options of laser plasma acceleration (LPA) for reaching a 100-GeV level energy by means of a multi-petawatt laser such as the 3.5-kJ, 500-fs PETawatt Aquitane Laser (PETAL) at French Alternative Energies and Atomic Energy Commission (CEA). Based on scaling of laser wakefield acceleration in the quasi-linear regime with the normalized vector potential a0 =1 .4(1.6), acceleration to 100 (130) GeV requires a 30-m-long plasma waveguide operated at the plasma density ne ≈ 7 × 10 15 cm −3 with a channel depth Δn/ne = 20%, while a nonlinear laser wakefield accelerator in the bubble regime with a0 2 can reach 100 GeV approximately in a 36/a0-m-long plasma through self-guiding. The third option is a hybrid concept that employs a ponderomotive channel created by a long leading pulse for guiding a short trailing driving laser pulse. The detail parameters for three options are evaluated, optimizing the operating plasma density at which a given energy gain is obtained over the dephasing length and the matched conditions for propagation of relativistic laser pulses in plasma channels, including the self-guiding. For the production of high-quality beams with 1%-level energy spread and a 1π-mm-mradlevel transverse normalized emittance at 100-MeV energy, a simple scheme based on the ionization-induced injection mechanism may be conceived. We investigate electron beam dynamics and effects of synchrotron radiation due to betatron motion by solving the beam dynamics equations on energy and beam radius numerically. For the bubble regime case with a0 = 4, radiative energy loss becomes 10% at the maximum energy of 90 GeV. OCIS codes: 350.4990, 350.5400. doi: 10.3788/COL201311.013501.

Subexawatt few-cycle lightwave generation via multipetawatt pulse compression

We identify the physical scenarios of nonlinear spatiotemporal dynamics of extreme-power laser fields enabling compression of a broad-beam ultrafast multipetawatt laser output to subexawatt few-cycle light pulses focusable to pulse intensities up to 1025W/cm2. We show that, with a careful control over the key limiting physical effects, which include dispersion, pulse self-steepening, small-scale self-focusing, and ionization effects, enhanced self-phase modulation of multipetawatt laser waveforms in a solid medium can provide spectral bandwidths compressible to few-cycle pulse widths with output beam profiles focusable to ultrarelativistic intensities.

Relativistic acceleration of micro-foils with prospects for fast ignition

AbstractIn this work, it is suggested that the ponderomotive force, induced by a multi-petawatt laser on the interface of a vacuum with solid target, can accelerate a micro-foil to relativistic velocities. The extremely high velocities of the micro-foil can be achieved due to the very short time duration (about a picosecond) of the laser pulse. This accelerated micro-foil is used to ignite a pre-compressed cylindrical shell containing the deuterium tritium fuel. The fast ignition is induced by a heat wave produced during the collision of the accelerated foil with the pre-compressed target. This approach has the advantage of separating geometrically the nanoseconds lasers that compress the target with the picosecond laser that accelerates the foil.

Numerical Simulation of Plasma-Based Raman Amplification of Laser Pulses to Petawatt Powers

Contemporary high-power laser systems make use of solid-state laser technology to reach petawatt pulse powers. The breakdown threshold for optical components in these systems, however, demands beam diameters up to 1 m. Raman amplification of laser beams promises a breakthrough by the use of much smaller amplifying media, i.e., millimeter-diameter-wide plasmas. Through the first large-scale multidimensional particle-in-cell simulations of this process, we have identified the parameter regime where multipetawatt peak laser powers can be reached, while the influence of damaging laser-plasma instabilities is only minor. Snapshots of the probe laser pulse being amplified, generated using state-of-the-art visualization techniques, are presented.

Atomic phase shifts in mixed-glass, multi-petawatt laser systems

The influence of the active gain medium on the spectral amplitude and phase of amplified, femtosecond pulses in a laser system is studied. Results from a case study of a 15-petawatt laser based on Nd-doped mixed glasses show that gain-induced atomic phase shifts will distort the pulses, reducing their peak power. It is also shown that a phase compensation solution is possible and the corresponding coefficients are calculated.

Ultra-high-contrast few-cycle pulses for multipetawatt-class laser technology

We report the generation of few-cycle multiterawatt light pulses with a temporal contrast of 10(10), when measured as close as 2 ps to the pulse's peak. Tens of picoseconds before the main pulse, the contrast value is expected to spread much beyond the measurement limit. Separate measurements of contrast improvement factors at different stages of the laser system indicate that real contrast values may reach 10(19) and 10(14), when measured 50 and 25 ps before the pulse's peak, respectively. The combination of the shortest pulse duration and the highest contrast renders our system a promising front-end architecture for future multipetawatt laser facilities.

Intense high-quality medical proton beams via laser fields

Simulations based on the coupled relativistic equations of motion show that protons stemming from laser-plasma processes can be efficiently post-accelerated employing single and crossed pulsed laser beams focused to spot radii on the order of the laser wavelength. We demonstrate that the crossed beams produce quasi-monoenergetic accelerated protons with kinetic energies exceeding 200 MeV, small energy spreads of about 1% and high densities as required for hadron cancer therapy. To our knowledge, this is the first scheme allowing for this important application based on an all-optical set-up.

Experimental demonstration of a synthetic aperture compression scheme for multi-Petawatt high-energy lasers

We present the experimental demonstration of a subaperture compression scheme achieved in the PETAL (PETawatt Aquitaine Laser) facility. We evidence that by dividing the beam into small subapertures fitting the available grating size, the sub-beam can be individually compressed below 1 ps, synchronized below 50 fs and then coherently added thanks to a segmented mirror.

Overview of PETAL, the multi-Petawatt project on the LIL facility

A multi-Petawatt high-energy laser PETAL coupled to the Ligne d'Intégration Laser (LIL) is under construction in the Aquitaine Region in France. This Petawatt laser will be dedicated to academic experiments in the fields of high energy density physics and ultra high intensity. Nd : glass laser chain coupled with the chirped pulse amplification (CPA technique allows delivery of high energy. Optical parametric CPA for pre-amplification and a new compression scheme will be implemented. PETAL is designed to deliver 3.6 kJ of energy in 500 fs on a target corresponding to 7.2 PW. The PETAL beam linked to the up to 60 kJ ns UV beams from the LIL will present new scientific research opportunities.

Efficient aberrations pre-compensation and wavefront correction with a deformable mirror in the middle of a petawatt-class CPA laser system

AbstractIn this paper, we describe the experimental validation of the technique of correction of wavefront aberration in the middle of the laser amplifying chain. This technique allows the correction of the aberrations from the first part of the laser system, and the pre-compensation of the aberrations built in the second part. This approach will allow an effective aberration management in the laser chain, to protect the optical surfaces and optimize performances, and is the only possible approach for multi-petawatt laser system from the technical and economical point of view. This approach is now possible after the introduction of new deformable mirrors with lower static aberrations and higher dynamic than the standard devices.

Design of PETAL multipetawatt high-energy laser front end based on optical parametric chirped pulse amplification

We report on a single shot optical parametric chirped pulse amplifier designed to seed the Petawatt Aquitaine Laser on the Laser Integration Line facility multipetawatt high-energy laser. The scheme is based on a stretched signal pulse at 1053 nm amplified with 20% conversion efficiency by a monomode pump pulse at 527 nm. The homemade pump laser is able to deliver a single shot beam with a square flat top spatial profile and programmable temporal shape. A high-stability 150 mJ, 8 nm, and 4.5 ns stretched pulse is then obtained with an excellent quality spatially shaped beam.

Focusing of high-current laser-driven ion beams

Using a two-dimensional relativistic hydrodynamic code, it is shown that a dense high-current ion beam driven by a short-pulse laser can be effectively focused by curving the target front surface. The focused beam parameters essentially depend on the density gradient scale length of the preplasma Ln and the surface curvature radius RT. When Ln⩽0.5λL (λL is the laser wavelength) and RT is comparable with the laser beam aperture dL, a significant fraction of the accelerated ions is focused on a spot much smaller than dL, which results in a considerable increase in the ion fluence and current density. Using high-contrast multipetawatt picosecond laser pulses of relativistic intensity (∼1020W∕cm2), focused ion (proton) current densities approaching those required for fast ignition of DT fuel seem to be feasible.

Synthetic aperture compression scheme for multi-petawatt high energy laser

An original synthetic aperture compressor scheme is proposed for multi-kilojoule petawatt beam. This scheme uses two compressor stages with multi-dielectric gratings allowing suppressing the mosaic of gratings. The main technical issues are detailed.

Design, optimization and development of pulse compression gratings for the MPW-HE LIL

The french Commissariat a l'Energie Atomique (CEA) develops a multipetawatt laser in the Laser Integration Line (LIL), prototype of the future Megajoule Laser [1]. This Petawatt laser line will deliver impulsions of 7.2 PW, 500 fs at the wavelength of 1053 nm. The chirped pulse amplification (CPA) method is used [2]. We work on the modelization and the fabrication of gratings used in the CPA scheme. Since damage threshold of more than 3 J/cm 2 @ 500fs are needed, we retained multidielectric gratings (MLD) instead of classical gold gratings. These gratings, developed in mid 90's, consist in a multidielectric mirror stack with its top layer engraved with a grating structure. We have been working to optimize the groove geometry of the MLD grating to minimize the E field maximum in the structure. An innovative design using a mixed metal/dielectric mirror stack was also studied. The scope of this paper is to present our main numerical results in these different domains.