Electron acceleration at grazing incidence of a subpicosecond intense laser pulse onto a plane solid target

Andreev, N. E.; Pugachev, Leonid; Povarnitsyn, M. E.; Levashov, P. R.

doi:10.1017/s0263034615001032

Cited by 20 publications

(10 citation statements)

References 27 publications

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“…It was shown that a preplasma of a near critical electron density supports the generation of a significant fraction of MeV electrons [9][10][11]. Simulations of the MeV-electron spectral distribution and fraction in dependence on the preplasma scale length L p made in [12] showed dramatic increase in the hot electron temperature and conversion efficiency by increasing of the plasma scale length from L p =50 up to 500.…”

Section: Introductionmentioning

confidence: 99%

Generation of keV hot near-solid density plasma states at high contrast laser-matter interaction

Rosmej

Samsonova

Höfer³

et al. 2018

Physics of Plasmas

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We present experimental evidence of ultra-high energy density plasma states with the keV bulk electron temperatures and near-solid electron densities generated during the interaction of high contrast, relativistically intense laser pulses with planar metallic foils. Experiments were carried out with the Ti:Sapphire laser system where a picosecond pre-pulse was strongly reduced by the conversion of the fundamental laser frequency into 2.Complex diagnostics setup was used for evaluation of the electron energy distribution in a wide energy range. The bulk electron temperature and density have been measured using x-ray spectroscopy tools; the temperature of supra-thermal electrons traversing the target was determined from measured bremsstrahlung spectra; run-away electrons were detected using magnet spectrometers. The measured electron energy distribution was in a good agreement with results of Particle-in-Cell (PIC) simulations. Analysis of the bremsstrahlung spectra and results on measurements of the run-away electrons showed a suppression of the hot electrons production in the case of the high laser contrast. Characteristic x-ray radiation has been used for evaluation of the bulk electron temperature and density. The measured Ti line radiation was simulated both in a steady-state and a transient approaches using the code FLYCHK that accounts for the atomic multi-level population kinetics. The best agreement between the measured and the synthetic spectrum of Ti was achieved at 1.8 keV electron temperatures and 2×10 23 cm -3 electron density.By application of Ti-foils covered with nm-thin Fe-layers we demonstrated that the thickness of the created keV hot dense plasma doesn't exceed 150nm. Results of the pilot hydro-dynamic simulations that are based on a wide-range two-temperature EOS, wide-range description of all transport and optical properties, ionization, electron and radiative heating, plasma expansion, and Maxwell equations (with a wide-range permittivity) for description of the laser absorption are in excellent agreement with experimental results. According to these simulations, the generation of keV-hot bulk electrons is caused by the collisional mechanism of the laser pulse absorption in plasmas with a near solid step-like electron density profile. The laser energy firstly deposited into the nm-thin skin-layer is then transported into the target depth by the electron heat conductivity. This scenario is opposite to the volumetric character of the energy deposition produced by supra-thermal electrons.Key words: relativistic laser-matter interaction; high laser contrast; electron energy distribution; x-ray spectroscopy; radiation of highly charged ions. I.

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Section: Introductionmentioning

confidence: 99%

Generation of keV hot near-solid density plasma states at high contrast laser-matter interaction

Rosmej

Samsonova

Höfer³

et al. 2018

Physics of Plasmas

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“…However, those schemes require an external electron injector which should be synchronized with the laser pulses on a femtosecond scale. Another approach is based on the interaction of a laser pulse with dense planar targets [16][17][18][19][20][21][22], structured targets [23][24][25] or waveguides [26 and 27], which allows production of subfemtosecond multi-MeV electron bunches which usually a) Electronic mail: dms@appl.sci-nnov.ru have high charge because of the high electron density of the target. Producing such sources of energetic electron bunches is of much interest among experimentalists over the last few years [20, 23, 24, and 28].…”

Section: Introductionmentioning

confidence: 99%

Near-surface electron acceleration during intense laser–solid interaction in the grazing incidence regime

2017

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When a relativistically intense p-polarized laser pulse is grazingly incident onto a planar solid-state target, a slightly superluminal field structure is formed near the target surface due to the incident and reflected waves superposition. This field structure can both extract the electrons from the target and accelerate them. It is theoretically shown that the acceleration is possible and stable for a wide range of electron initial conditions. PIC simulations confirm that this mechanism can actually take place for realistic parameters. As a result, the electron bunches with charge of tens of nC and GeV-level energy can be produced using a laser intensity 10 21 -10 22 W/cm 2 . It is also shown that the presence of a preplasma can increase the acceleration rate, which becomes possible because of more efficient electron injection into the accelerating field structure.

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“…The targets range from solid density with sharp boundaries to extended low density gas. In solids, the mechanism strongly depends on the gradients of the pre-plasma on the target surface and can be the vacuum/Brunel [7], resonant absorption in critical density, the ponderomotive and the (J×B) mechanism of acceleration [8,9] or stochastic heating [10][11][12][13] etc. Laser interaction with low density gas targets provides an effective acceleration of electrons to high energies in the wakefields generated in preformed plasma channels [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…There are different mechanisms of laser energy transfer to high energy electrons depending on the laser parameters and the type of targets from solid density targets with sharp boundary to extended low density gas targets. In solids, the mechanism strongly depends on gradients of the preplasma on the target surface and can be the vacuum/Brunel [7], resonant absorption in critical density, the ponderomotive or (JxB) mechanism of acceleration [8,9], stochastic heating [10][11][12][13] etc.…”

Section: Introductionmentioning

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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Electron acceleration at grazing incidence of a subpicosecond intense laser pulse onto a plane solid target

Cited by 20 publications

References 27 publications

Generation of keV hot near-solid density plasma states at high contrast laser-matter interaction

Generation of keV hot near-solid density plasma states at high contrast laser-matter interaction

Near-surface electron acceleration during intense laser–solid interaction in the grazing incidence regime

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

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