Modern high-power lasers can generate extreme states of matter that are relevant to astrophysics, equation-of-state studies and fusion energy research. Laser-driven implosions of spherical polymer shells have, for example, achieved an increase in density of 1,000 times relative to the solid state. These densities are large enough to enable controlled fusion, but to achieve energy gain a small volume of compressed fuel (known as the 'spark') must be heated to temperatures of about 108 K (corresponding to thermal energies in excess of 10 keV). In the conventional approach to controlled fusion, the spark is both produced and heated by accurately timed shock waves, but this process requires both precise implosion symmetry and a very large drive energy. In principle, these requirements can be significantly relaxed by performing the compression and fast heating separately; however, this 'fast ignitor' approach also suffers drawbacks, such as propagation losses and deflection of the ultra-intense laser pulse by the plasma surrounding the compressed fuel. Here we employ a new compression geometry that eliminates these problems; we combine production of compressed matter in a laser-driven implosion with picosecond-fast heating by a laser pulse timed to coincide with the peak compression. Our approach therefore permits efficient compression and heating to be carried out simultaneously, providing a route to efficient fusion energy production.

Rapid heating of a compressed fusion fuel by a short-duration laser pulse is a promising route to generating energy by nuclear fusion, and has been demonstrated on an experimental scale using a novel fast-ignitor geometry. Here we describe a refinement of this system in which a much more powerful, pulsed petawatt (10(15) watts) laser creates a fast-heated core plasma that is scalable to full-scale ignition, significantly increasing the number of fusion events while still maintaining high heating efficiency at these substantially higher laser energies. Our findings bring us a step closer to realizing the production of relatively inexpensive, full-scale fast-ignition laser facilities.

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Articles you may be interested inA highly miniaturized electron and ion energy spectrometer prototype for the rapid analysis of space plasmas Rev. Sci. Instrum. 85, 023305 (2014); 10.1063/1.4865842 High energy electron crystal spectrometer Rev. Sci. Instrum. 80, 076106 (2009); 10.1063/1.3170508 Absolute calibration of an electron spectrometer using high energy electrons produced by the laser-plasma interaction Rev. Sci. Instrum. 79, 083301 (2008); 10.1063/1.2969655 Absolute calibration of image plates for electrons at energy between 100 keV and 4 MeV Rev. Sci. Instrum. 79, 033301 (2008); 10.1063/1.2885045 A high sensitivity electron momentum spectrometer with simultaneous detection in energy and momentum Rev.A high energy electron spectrometer has been designed and tested using imaging plate (IP). The measurable energy range extends from 1 to 100 MeV or even higher. The IP response in this energy range is calibrated using electrons from L-band and S-band LINAC accelerator at energies 11.5, 30, and 100 MeV. The calibration has been extended to 0.2 MeV using an existing data and Monte Carlo simulation Electron Gamma Shower code. The calibration results cover the energy from 0.2 to 100 MeV and show almost a constant sensitivity for electrons over 1 MeV energy. The temperature fading of the IP shows a 40% reduction after 80 min of the data taken at 22.5°C. Since the fading is not significant after this time we set the waiting time to be 80 min. The oblique incidence effect has been studied to show that there is a 1 / cos relation when the incidence angle is .

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The development of ultra-intense lasers has facilitated new studies in laboratory astrophysics and high-density nuclear science, including laser fusion. Such research relies on the efficient generation of enormous numbers of high-energy charged particles. For example, laser-matter interactions at petawatt (10(15) W) power levels can create pulses of MeV electrons with current densities as large as 10(12) A cm(-2). However, the divergence of these particle beams usually reduces the current density to a few times 10(6) A cm(-2) at distances of the order of centimetres from the source. The invention of devices that can direct such intense, pulsed energetic beams will revolutionize their applications. Here we report high-conductivity devices consisting of transient plasmas that increase the energy density of MeV electrons generated in laser-matter interactions by more than one order of magnitude. A plasma fibre created on a hollow-cone target guides and collimates electrons in a manner akin to the control of light by an optical fibre and collimator. Such plasma devices hold promise for applications using high energy-density particles and should trigger growth in charged particle optics.

In order to achieve a high-quality, i.e., monoenergetic, intense ion beam, we propose the use of a double-layer target. The first layer, at the target front, consists of high-Z atoms, while the second (rear) layer is a thin coating of low-Z atoms. The generation of high-quality proton beams from the double-layer target, irradiated by an ultraintense laser pulse, is demonstrated with three-dimensional particle-in-cell simulations.

In an inhomogeneous plasma, low-frequency solitary waves, generated by superintense laser pulses, are accelerated towards the plasma-vacuum interface where they radiate their energy in the form of lowfrequency electromagnetic bursts. The transverse inhomogeneity of the plasma inside the self-focusing radiation channel leads to guiding of the solitary waves. These solitary waves excite a two-ribbon magnetic field structure in their wake. These phenomena have been studied with two-dimensional particle-in-cell simulations and are expected to be observed in present-day laser-plasma experiments. PACS numbers: 52.35.Sb, 52.40.Nk, 52.60. + h, 52.65.Rr The intensity of the light emitted by present-day lasers has exceeded by a good margin the value where the electron quiver energy becomes relativistic [1]. When propagating in a plasma this superintense laser radiation displays the effects of relativistic nonlinearities such as relativistic self-focusing [2], relativistic transparency of an overdense plasma [3], and the generation of relativistic solitary waves [4].Relativistic solitons were predicted to occur when high intensity laser pulses interact with a plasma [5][6][7]. Recently, relativistic solitary waves were discovered in two spatial and three velocity dimensions (2D3V) particle-incell (PIC) simulations [4] (in the following we shall use the shorter term "soliton," bearing in mind, however, that the interaction between solitons has to be investigated further). These solitons are generated behind the laser pulse and are made of low-frequency, nonlinear, spatially localized electromagnetic fields with almost zero group velocity.As shown in Ref.[4] nearly 30%-40% of the laser pulse energy can be transformed into solitons. This fairly high efficiency of electromagnetic energy transformation indicates that solitary waves, which are an essential component of turbulence in fluids and plasmas, can play an important role in the development of the interaction between the laser pulse and the plasma.In homogeneous plasmas the solitons remain, for a long time, close to the region where they were generated, and eventually decay due to their interaction with fast electrons. In this case, the soliton energy is transformed into fast particle energy. However a real plasma is always inhomogeneous. In a nonuniform dispersive medium a wave packet moves according to the well-known equations of geometric optics: ᠨwhere the Hamiltonian is the wave frequency H ͑x i , k i ͒ v q k 2 c 2 1 v 2 pe . If we model the spatial dependence of the Langmuir frequency in a plasma channel localized in the y direction and inhomogeneous in the x direction as v 2 pe v 2 pe0 ͑1 1 x͞L x 1 y 2 ͞L 2 y ͒, we find for the components of the wave packet accelerationẍ 2c 2 ͞2L x andÿ 2yc 2 ͞L 2 y . The wave packet is accelerated along the x axis toward the low density side, and oscillates in the transverse direction with frequency c͞L y .The propagation in inhomogeneous media of solitons described by the nonlinear Schrödinger equation was discussed in Ref. [8]...