P3: An installation for high-energy density plasma physics and ultra-high intensity laserematter interaction at ELI-Beamlines

ELI-Beamlines(ELI-BL),one of the three pillars of the Extreme Light Infrastructure endeavour,will be in a unique position to perform research in high-energy-density-physics(HEDP),plasma physics and ultra-high intensity(UHI)ð>10^(22) W=cm^(2)) lasereplasma interaction.Recently the need for HED laboratory physics was identified and the P3(plasma physics platform)installation under construction in ELI-BL will be an answer.The ELI-BL 10 PW laser makes possible fundamental research topics from high-field physics to new extreme states of matter such as radiation-dominated ones,high-pressure quantum ones,warm dense matter(WDM)and ultra-relativistic plasmas.HEDP is of fundamental importance for research in the field of laboratory astrophysics and inertial confinement fusion(ICF).Reaching such extreme states of matter now and in the future will depend on the use of plasma optics for amplifying and focusing laser pulses.This article will present the relevant technological infrastructure being built in ELI-BL for HEDP and UHI,and gives a brief overview of some research under way in the field of UHI,laboratory astrophysics,ICF,WDM,and plasma optics.

The L4n laser beamline of the P3-installation:Towards high-repetition rate high-energy density physics at ELI-Beamlines

The P3 installation of ELI-Beamlines is conceived as an experimental platform for multiple high-repetition-rate laser beams spanning time scales from femtosecond via picosecond to nanosecond.The upcoming L4n laser beamline will provide shaped nanosecond pulses of up to 1.9 kJ at a maximum repetition rate of 1 shot/min.This beamline will provide unique possibilities for high-pressure,high-energy-density physics,warm dense matter,and laser–plasma interaction experiments.Owing to the high repetition rate,it will become possible to obtain considerable improvements in data statistics,in particular,for equation-of-state data sets.The nanosecond beam will be coupled with short sub-picosecond pulses,providing high-resolution diagnostic tools by either irradiating a backlighter target or driving a betatron setup to generate energetic electrons and hard X-rays.

Metrology for sub-Rayleigh-length target positioning in~10^(22)W/cm^(2)laser-plasma experiments

Tight focusing with very small f-numbers is necessary to achieve the highest at-focus irradiances.However,tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target irradiance We describe several near-infrared,visible,ultraviolet and soft and hard X-ray diagnostics employed in a~10^(22)W/cm^(2)laser±plasma experiment.We used nearly 10 J total energy femtosecond laser pulses focused into an approximately1.3-μm focal spot on 5±20μm thick stainless-steel targets.We discuss the applicability of these diagnostics to determine the best in-focus target position with approximately 5μm accuracy(i.e.,around half of the short Rayleigh length)and show that several diagnostics(in particular,3ωreflection and on-axis hard X-rays)can ensure this accuracy.We demonstrated target positioning within several micrometers from the focus,ensuring over 80%of the ideal peak laser intensity on-target.Our approach is relatively fast(it requires 10±20 laser shots)and does not rely on the coincidence of low-power and high-power focal planes.

Avalanche boron fusion by laser picosecond block ignition with magnetic trapping for clean and economic reactor

Measured highly elevated gains of proton–boron(HB11) fusion(Picciotto et al., Phys. Rev. X 4, 031030(2014))confirmed the exceptional avalanche reaction process(Lalousis et al., Laser Part. Beams 32, 409(2014); Hora et al.,Laser Part. Beams 33, 607(2015)) for the combination of the non-thermal block ignition using ultrahigh intensity laser pulses of picoseconds duration. The ultrahigh acceleration above 10^(20) cm s^(-2)for plasma blocks was theoretically and numerically predicted since 1978(Hora, Physics of Laser Driven Plasmas(Wiley, 1981), pp. 178 and 179) and measured(Sauerbrey, Phys. Plasmas 3, 4712(1996)) in exact agreement(Hora et al., Phys. Plasmas 14, 072701(2007)) when the dominating force was overcoming thermal processes. This is based on Maxwell's stress tensor by the dielectric properties of plasma leading to the nonlinear(ponderomotive) force f_(NL)resulting in ultra-fast expanding plasma blocks by a dielectric explosion. Combining this with measured ultrahigh magnetic fields and the avalanche process opens an option for an environmentally absolute clean and economic boron fusion power reactor. This is supported also by other experiments with very high HB11 reactions under different conditions(Labaune et al., Nature Commun.4, 2506(2013)).

Design,installation and commissioning of the ELI-Beamlines high-power,high-repetition rate HAPLS laser beam transport system to P3

The design and the early commissioning of the ELI-Beamlines laser facility’s 30 J,30 fs,10 Hz HAPLS(High-repetitionrate Advanced Petawatt Laser System)beam transport(BT)system to the P3 target chamber are described in detail.It is the world’s first and with 54 m length,the longest distance high average power petawatt(PW)BT system ever built.It connects the HAPLS pulse compressor via the injector periscope with the 4.5 m diameter P3 target chamber of the plasma physics group in hall E3.It is the largest target chamber of the facility and was connected first to the BT system.The major engineering challenges are the required high vibration stability mirror support structures,the high pointing stability optomechanics as well as the required levels for chemical and particle cleanliness of the vacuum vessels to preserve the high laser damage threshold of the dielectrically coated high-power mirrors.A first commissioning experiment at low pulse energy shows the full functionality of the BT system to P3 and the novel experimental infrastructure.

Fast magnetic energy dissipation in relativistic plasma induced by high order laser modes

Fast magnetic field annihilation in a collisionless plasma is induced by using TEM(1,0) laser pulse. The magnetic quadrupole structure formation, expansion and annihilation stages are demonstrated with 2.5-dimensional particle-in-cell simulations. The magnetic field energy is converted to the electric field and accelerate the particles inside the annihilation plane. A bunch of high energy electrons moving backwards is detected in the current sheet. The strong displacement current is the dominant contribution which induces the longitudinal inductive electric field.

Radial density profile and stability of capillary discharge plasma waveguides of lengths up to 40 cm

We measured the parameter reproducibility and radial electron density profile of capillary discharge waveguides with diameters of 650µm to 2 mm and lengths of 9 to 40 cm.To the best of the authors’knowledge,40 cm is the longest discharge capillary plasma waveguide to date.This length is important for≥10 GeV electron energy gain in a single laser-driven plasma wakefield acceleration stage.Evaluation of waveguide parameter variations showed that their focusing strength was stable and reproducible to<0.2%and their average on-axis plasma electron density to<1%.These variations explain only a small fraction of laser-driven plasma wakefield acceleration electron bunch variations observed in experiments to date.Measurements of laser pulse centroid oscillations revealed that the radial channel profile rises faster than parabolic and is in excellent agreement with magnetohydrodynamic simulation results.We show that the effects of non-parabolic contributions on Gaussian pulse propagation were negligible when the pulse was approximately matched to the channel.However,they affected pulse propagation for a non-matched configuration in which the waveguide was used as a plasma telescope to change the focused laser pulse spot size.