The role of fast electron energy transfer in the problem of shock ignition of laser thermonuclear target

Gus’kov, S. Yu.; Kuchugov, P. A.; Yakhin, R. A.; Змитренко, Н. В.

doi:10.1016/j.hedp.2020.100835

Cited by 8 publications

(16 citation statements)

References 26 publications

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“…In this scheme, the role of HE is also not fully understood, since they are generated when the fuel capsule is already strongly compressed with a shell areal density of ⟨ρr⟩ ∼ 50 − 80 g/cm 2 , so that the range of HE can be smaller or larger than the thickness of the compressed shell, depending on their energy 11 . According to recent works 12,13 , low energy HE of few tens of keV could be stopped in the compressed shell, with the beneficial effect of reinforcing the ignitor shock, while HE with energy higher than ∼ 100 keV could cross the shell and preheat the fuel.…”

Section: Introductionmentioning

confidence: 99%

Investigation on the origin of hot electrons in laser plasma interaction at shock ignition intensities

Cristoforetti

Baffigi

Batani

et al. 2023

Preprint

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Shock Ignition is a two-step scheme to reach Inertial Confinement Fusion, where the precompressed fuel capsule is ignited by a strong shock driven by an intense laser pulse at intensity ∼ 1016 W/cm2. In this report we detail the results of an experiment designed to investigate the origin of hot electrons (HE) in laser-plasma interaction at intensities and plasma temperatures expected for Shock Ignition. A detailed time- and spectrally-resolved characterization of Stimulated Raman Scattering (SRS) and Two Plasmon Decay (TPD) instabilities, as well as of the generated HE, suggest that SRS is the dominant source of HE via the damping of daughter plasma waves. The temperature dependence of laser plasma instabilities was also investigated, enabled by the use of different ablator materials, suggesting that TPD is damped at earlier times for higher plasma temperatures, due to the Landau damping effect. The identification of the predominant HE source and the effect of plasma temperature on laser plasma interaction, here investigated, are extremely useful for developing the mitigation strategies for reducing the impact of HE on the fuel ignition.

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Section: Introductionmentioning

confidence: 99%

Investigation on the origin of hot electrons in laser plasma interaction at shock ignition intensities

Cristoforetti

Baffigi

Batani

et al. 2023

Preprint

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“…Energy transfer into the deep regions of the compressible part of the target and, especially, into deuterium-tritium (DT)-fuel plays a negative role, since it leads to an increase in the back-pressure, which prevents the target from being compressed [35][36][37]. On the contrary, energy transfer to the region of subsonic flow of relatively dense matter of the evaporated part of target (corona) as well as to the external region of dense ablator plays a positive role, which consists in increasing the pressure that compresses the target (ablation pressure) [38][39][40]. In a conventional sparkignition target with a relatively low laser energy conversion into fast-electron energy, only the negative effect of compressible target's part preheating is manifested [4,18,21,41].…”

Section: Introductionmentioning

confidence: 99%

“…In a conventional sparkignition target with a relatively low laser energy conversion into fast-electron energy, only the negative effect of compressible target's part preheating is manifested [4,18,21,41]. In shock-ignited targets, depending on the energy contained in fast electrons and their temperature, both the negative and the positive effects of energy transfer by these particles are manifested [40].…”

Section: Introductionmentioning

confidence: 99%

“…In shock ignition, the issue of energy transfer by laseraccelerated electrons is of key importance. In [25,40,42,43], the fact was substantiated that fast electrons make a decisive contribution to the formation of ablation pressure of 500-1000 Mbar, which is necessary to generate an igniting shock wave, upon combined heating of the target when 20%-40% of the heating energy is contained in the energy of these particles. Such a powerful shock wave can reliably provide a high gain (ratio of thermonuclear energy to absorbed laser energy) of about 100 in a target of a traditional design in the form of a two-layer shell with an external inert ablator [7,21,25].…”

Section: Introductionmentioning

confidence: 99%

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Fast-electron maintaining a high shock-ignition gain with a significant decrease in the laser pulse energy

Gus’kov¹,

Demchenko²,

Dmitriev³

et al. 2022

Plasma Phys. Control. Fusion

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The effect of energy transfer by laser-accelerated fast electrons on thermonuclear gain of a shock- ignited ICF target at the different power and duration of high-intensity part of the laser pulse (spike) responsible for igniting shock wave generation has been investigated on the basis of hydro-kinetic numerical simulations. The key result of these studies is that the fast-electron energy transfer is able to provide a great contribution to igniting shock wave pressure to maintain a high thermonuclear gain with a significant decrease in the energy of the igniting part of laser pulse. Calculations were performed for the 2nd harmonic Nd-laser pulse in order to justify shock-ignition experiments on MJ-class facility, which is under construction in Russia now. Spike energy conversion to fast electron energy and its temperature were selected in the ranges, which are discussed in the literature. It has been found that fast electrons with a temperature of 50-70 keV, whose energy contains 20-40% of spike energy, make so large contribution to the pressure of igniting shock wave that the gain factor retains its value of 70-80 with spike energy decrease by 1.5-2 times.

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“…The deleterious effect of preheat 27 outweighs the benefit of drive support for hot electrons with a population temperature higher than 30keV or mono-energetic hot electron populations with an energy exceeding ∼ 50keV (target dependant). Conversely, there is evidence that kinetically modelled hot-electrons can provide benefit to implosion performance across a broad range of population temperatures [28][29][30] (up to 70keV). Within these simulations the LPI scattered light energy fraction is not explicitly related to the LPI hot-electron energy fraction which may explain the difference in impact of hot electrons compared to those that use simplified LPI models.…”

Section: Introductionmentioning

confidence: 99%

Role of hot electrons in shock ignition constrained by experiment at the National Ignition Facility

et al. 2022

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Shock ignition is a scheme for direct drive inertial confinement fusion that offers the potential for high gain with the current generation of laser facility; however, the benefits are thought to be dependent on the use of low adiabat implosions without laser–plasma instabilities reducing drive and generating hot electrons. A National Ignition Facility direct drive solid target experiment was used to calibrate a 3D Monte Carlo hot-electron model for 2D radiation-hydrodynamic simulations of a shock ignition implosion. The [Formula: see text] adiabat implosion was calculated to suffer a 35% peak areal density decrease when the hot electron population with temperature [Formula: see text] and energy [Formula: see text] was added to the simulation. Optimizing the pulse shape can recover [Formula: see text] of the peak areal density lost due to a change in shock timing. Despite the harmful impact of laser–plasma instabilities, the simulations indicate shock ignition as a viable method to improve performance and broaden the design space of near ignition high adiabat implosions.

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The role of fast electron energy transfer in the problem of shock ignition of laser thermonuclear target

Cited by 8 publications

References 26 publications

Investigation on the origin of hot electrons in laser plasma interaction at shock ignition intensities

Investigation on the origin of hot electrons in laser plasma interaction at shock ignition intensities

Fast-electron maintaining a high shock-ignition gain with a significant decrease in the laser pulse energy

Role of hot electrons in shock ignition constrained by experiment at the National Ignition Facility

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