Optimization of electron acceleration by short laser pulses from low-density targets

Lobok, M. G.; Brantov, A. V.; Gozhev, D. A.; Bychenkov, V. Yu.

doi:10.1088/1361-6587/aaca79

Cited by 23 publications

(26 citation statements)

References 18 publications

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“…In recent simulations [46], 30 fs, 4 J laser pulse of 8×10 20 W cm −2 intensity interacted with an ionized planar target. A target electron density was varied from 0.05 n cr up to 2 n cr and a layer thickness from 10λ up to 500λ.…”

Section: Results Of Modeling and Comparison With Experimental Datamentioning

confidence: 99%

Interaction of relativistically intense laser pulses with long-scale near critical plasmas for optimization of laser based sources of MeV electrons and gamma-rays

et al. 2019

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Experiments were performed to study electron acceleration by intense sub-picosecond laser pulses propagating in sub-mm long plasmas of near critical electron density (NCD). Low density foam layers of 300-500 μm thickness were used as targets. In foams, the NCD-plasma was produced by a mechanism of super-sonic ionization when a well-defined separate ns-pulse was sent onto the foamtarget forerunning the relativistic main pulse. The application of sub-mm thick low density foam layers provided a substantial increase of the electron acceleration path in a NCD-plasma compared to the case of freely expanding plasmas created in the interaction of the ns-laser pulse with solid foils. The performed experiments on the electron heating by a 100 J, 750 fs short laser pulse of 2-5×10 19 W cm −2 intensity demonstrated that the effective temperature of supra-thermal electrons increased from 1.5-2 MeV in the case of the relativistic laser interaction with a metallic foil at high laser contrast up to 13 MeV for the laser shots onto the pre-ionized foam. The observed tendency towards a strong increase of the mean electron energy and the number of ultra-relativistic laseraccelerated electrons is reinforced by the results of gamma-yield measurements that showed a 1000fold increase of the measured doses. The experiment was supported by 3D-PIC and FLUKA simulations, which considered the laser parameters and the geometry of the experimental set-up. Both, measurements and simulations showed a high directionality of the acceleration process, since the strongest increase in the electron energy, charge and corresponding gamma-yield was observed close to the direction of the laser pulse propagation. The charge of super-ponderomotive electrons with energy above 30 MeV reached a very high value of 78 nC.

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Section: Results Of Modeling and Comparison With Experimental Datamentioning

confidence: 99%

Interaction of relativistically intense laser pulses with long-scale near critical plasmas for optimization of laser based sources of MeV electrons and gamma-rays

et al. 2019

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“…2. This thickness, which is inversely proportional to target density, l opt ∝ a 0 /n e , is determined by the length of laser pulse depletion due to pulse etching [12] that was used to interpret the PIC simulations [3,9].…”

Section: Laser Pulse Propagation and Electron Generation In A Sumentioning

confidence: 99%

“…The considered acceleration regime is quite different from the standard bubble regime with conditions opposite to those in Ref. [2], L > λ p , d, [3] and occurs when the nonlinear 3D charge-separation structure travels as a stable elongated laser field-filled cavity over many Rayleigh lengths in a dense gas plasma, more like a "laser bullet" than an empty bubble.…”

Section: Introductionmentioning

confidence: 96%

“…We recently performed a preliminary study to determine the optimal density and thickness of planar low-density targets maximizing the number of high-energy electrons generated by a femtosecond laser pulse with a given intensity [3]. The interest in such a study is related to laser generation of electron bunches that can produce hard γ-quanta suitable for radiography of dense thick samples with γ-energy of a few MeV, electron-positron pairs, different (γ, n) reactions for neutron generation, and even light mesons.…”

Section: Introductionmentioning

confidence: 99%

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Generation of high-charge electron beam in a subcritical-density plasma through laser pulse self-trapping

Bychenkov¹,

Lobok²,

Kovalev³

et al. 2019

Plasma Phys. Control. Fusion

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To maximize the charge of a high-energy electron beam accelerated by an ultra-intense laser pulse propagating in a subcritical plasma, the pulse length should be longer than both the plasma wavelength and the laser pulse width, which is quite different from the standard bubble regime.In addition, the laser-plasma parameters should be chosen to produce the self-trapping regime of relativistic channeling, where the diffraction divergence is balanced by the relativistic nonlinearity such that the laser beam radius is unchanged during pulse propagation in a plasma over many Rayleigh lengths. The condition for such a self-trapping regime is the same as what was empirically found in several previous simulation studies in the form of the pulse width matching condition.Here, we prove these findings for a subcritical plasma, where the total charge of high-energy electrons reaches the multi-nC level, by optimization in a 3D PIC simulation study and compare the results with an analytic theory of relativistic self-focusing. A very efficient explicitly demonstrated generation of high-charge electron beams opens a way to a high-yield production of gammas, positrons, and photonuclear particles.

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“…L > λ p , d [4]. Electron acceleration occurs in a traveling nonlinear 3D charge-separation structure as an elongated cavity (laser bullet) filled with a laser field and not in an empty bubble [3].…”

Section: Introductionmentioning

confidence: 99%

Effective production of gammas, positrons, and photonuclear particles from optimized electron acceleration by short laser pulses in low-density targets

2019

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Electron acceleration has been optimized based on 3D PIC simulations of a short laser pulse interacting with low-density plasma targets to find the pulse propagation regime that maximizes the charge of high-energy electron bunches. This regime corresponds to laser pulse propagation in a self-trapping mode where the diffraction divergence is balanced by the relativistic nonlinearity such that relativistic self-focusing on the axis does not happen and the laser beam radius stays unchanged during pulse propagation in a plasma over many Rayleigh lengths. Such a regime occurs for a nearcritical density if the pulse length considerably exceeds both the plasma wavelength and the pulse width. Electron acceleration occurs in a traveling cavity filled with a high-frequency laser field and a longitudinal electrostatic single-cycle field ("self-trapping regime"). Monte Carlo simulations demonstrated a high electron yield that allows an efficient production of gamma radiation, electronpositron pairs, neutrons, and even pions from a catcher-target.

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Optimization of electron acceleration by short laser pulses from low-density targets

Cited by 23 publications

References 18 publications

Interaction of relativistically intense laser pulses with long-scale near critical plasmas for optimization of laser based sources of MeV electrons and gamma-rays

Interaction of relativistically intense laser pulses with long-scale near critical plasmas for optimization of laser based sources of MeV electrons and gamma-rays

Generation of high-charge electron beam in a subcritical-density plasma through laser pulse self-trapping

Effective production of gammas, positrons, and photonuclear particles from optimized electron acceleration by short laser pulses in low-density targets

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