Plasma channel formation in the knife-like focus of laser beam

The plasma channel formation in the focus of a knife-like nanosecond laser pulse irradiating a gas target is studied theoretically, and in gas-dynamics computer simulations. The distribution of the electromagnetic field in the focus region, obtained analytically, is used to calculate the energy deposition in the plasma, which then is implemented in the magnetohydrodynamic computer code. The modelling of the channel evolution shows that the plasma profile, which can guide the laser pulse, is formed by the tightly focused short knife-like lasers. The results of the simulations show that a proper choice of the convergence angle of a knife-like laser beam (determined by the focal length of the last cylindrical lens), and laser pulse duration may provide a sufficient degree of azimuthal symmetry of the formed plasma channel

Plasma channel formation in the knife-like focus of laser beam

The plasma channel formation in the focus of a knife-like nanosecond laser pulse irradiating a gas target is studied theoretically, and in gas-dynamics computer simulations. The distribution of the electromagnetic field in the focus region, obtained analytically, is used to calculate the energy deposition in the plasma, which then is implemented in the magnetohydrodynamic computer code. The modelling of the channel evolution shows that the plasma profile, which can guide the laser pulse, is formed by the tightly focused short knife-like lasers. The results of the simulations show that a proper choice of the convergence angle of a knife-like laser beam (determined by the focal length of the last cylindrical lens), and laser pulse duration may provide a sufficient degree of azimuthal symmetry of the formed plasma channel

Plasma channel formation in the knife-like focus of laser beam

The plasma channel formation in the focus of a knife-like nanosecond laser pulse irradiating a gas target is studied theoretically, and in gas-dynamics computer simulations. The distribution of the electromagnetic field in the focus region, obtained analytically, is used to calculate the energy deposition in the plasma, which then is implemented in the magnetohydrodynamic computer code. The modelling of the channel evolution shows that the plasma profile, which can guide the laser pulse, is formed by the tightly focused short knife-like lasers. The results of the simulations show that a proper choice of the convergence angle of a knife-like laser beam (determined by the focal length of the last cylindrical lens), and laser pulse duration may provide a sufficient degree of azimuthal symmetry of the formed plasma channel

Laser-plasma experiment at intensities approaching 10^22 W/cm^2

We present an overview of our first joint experiment devoted to achieving ultra-high on-target intensities, reaching efficient conversion of laser radiation to hard x-rays ("Gamma Flash"), and generating intense coherent soft x-rays (harmonics). We used the J-KAREN-P laser facility (KPSI QST) and irradiated solid targets with intensities approaching 10^22 W/cm^2. To get information on the interaction physics, we employed a broad range of diagnostics, including laser, plasma, secondary radiation (from NIR to MeV x-rays) and particles (e-, p+) diagnostics, and controlled preplasma using several laser contrast modes and additional artificial prepulse. We show first results on hard x-ray and harmonic generation, x-ray spectroscopy, and preplasma analysis.We thank the J-KAREN-P laser operation group. We acknowledge financial support from ELI-Beamlines, JSPS JP 19H00669, and QST Director Funds 創成的研究 16 and 創成的研究 20.2020 Annual (75th) JPS Meetin

Hard x-ray generation at intensity approaching 10^22 W/cm^2

Efficient generation of ~MeV x-rays in the Gamma Flare regime [1],[2] inpreplasma via the nonlinear Thomson/inverse Compton scattering mechanism[3] is one of the most promising and expected high-power laserapplications. The hard x-rays are generated by Bremsstrahlung as well,while the electrons go through the target [4],[5], which also includesmultiple passes (refluxing) [5],[6]. Simulations predict that at highintensities the preplasma x-rays dominate; however, at intensitiesavailable now, Bremsstrahlung dominates, so that the Gamma Flaremechanism is not yet demonstrated experimentally.We describe our experiment performed with the J-KAREN-P laser [7]-[9],with the emphasis on data from the scintillator-based hard x-rayspectrographs [10] (0.1 – 1 MeV) and Compton spectrograph [11] (2 – 10MeV), and our efforts to distinguish the generation mechanism.We thank the J-KAREN-P laser operation group. We acknowledge financialsupport from ELI-Beamlines, JSPS JP 19H00669, and QST Director Funds 創成的研究 16 and 創成的研究 20.[1] T. Nakamura, et al., "High-Power γ-Ray Flash Generation inUltraintense Laser-Plasma Interactions," Phys. Rev. Lett. 108, 195001 (2012).[2] C. P. Ridgers, et al., "Dense Electron-Positron Plasmas andUltraintense γ rays from Laser-Irradiated Solids," Phys. Rev. Lett. 108,165006 (2012).[3] K. V. Lezhnin, P. V. Sasorov, G. Korn, and S. V. Bulanov, "Highpower gamma flare generation in multi-petawatt laser interaction withtailored targets," Phys. Plasmas 25, 123105 (2018).[4] D. Wu, et al., "Characteristics of X/γ-ray radiations by intenselaser interactions with high-Z solids: The role of bremsstrahlung andradiation reactions," Matter Rad. Extremes 3, 293-299 (2018).[5] J. Vyskočil, O. Klimo, S. Weber, "Simulations of bremsstrahlungemission in ultra-intense laser interactions with foil targets," PlasmaPhys. Control. Fusion 60, 054013 (2018).[6] D. R. Rusby, et al., "Effect of rear surface fields on hot,refluxing and escaping electron populations via numerical simulations,"High Pow. Las. Sci. Eng. 7, e45 (2019).[7] A.S.Pirozhkov, et al., "Approaching the diffraction-limited,bandwidth-limited Petawatt," Opt. Express 25, 20486 (2017).[8] H. Kiriyama, et al., "High-contrast high-intensity repetitivepetawatt laser," Opt. Lett. 43, 2595 (2018).[9] H. Kiriyama, et al., "Experimental investigation on temporalcontrast of pre-pulses by post-pulses in a petawatt laser facility," Opt. Lett. (accepted).[10] D. R. Rusby, et al., "Novel scintillator-based x-ray spectrometerfor use on high repetition laser plasma interaction experiments," Rev.Sci. Instr. 89, 073502 (2018).[11] S. Singh, et al., "Compact high energy x-ray spectrometer based onforward Compton scattering for high intensity laser plasma experiments,"Rev. Sci. Instr. 89, 085118 (2018).OPTICS & PHOTONICS International Congress 202

Overview of the 10^22 Experiment

We present an overview of our recent experiment on achieving ultra-high on-target intensities, reaching efficient conversion of laser radiation to hard x-rays ("Gamma Flash"), and generating intense coherent soft x-rays (high-order harmonics). Our international team used the J-KAREN-P laser facility at KPSI QST and irradiated solid targets with intensities close to 1022 W/cm2. We employed a broad range of diagnostics, including laser, plasma, secondary radiation (from NIR to MeV x-rays) and particle (e-, p+) diagnostics, and controlled preplasma using several laser contrast modes and artificial prepulse. In this presentation we overview the experiment and simulations dedicated to it, and show first results on hard x-ray and harmonic generation, x-ray spectroscopy, and preplasma analysis.Opto-2020 Symposium on Photon and Beam Scienc

Overview of the 10^22 Experiment with the J-KAREN-P laser

Ultra-high intensities open a way towards Terawatt and potentially Petawatt gamma-ray pulses in the so called Gamma Flare regime. We performed our first experiment towards this regime with the J-KAREN-P laser operating at intensities close to 10^22 W/cm^2. In this presentation I will overview the experiment, including very bright hard x-ray generation (sub-MeV to a few-MeV spectral range), high-order harmonic generation (30 to 70 eV), and multiple additional diagnostics revealing information on preplasma (properties of reflected 1st, 2nd, and 3rd harmonics and back-reflection). I will compare these results with the integrated HD and PIC simulations.OPTO-2021 Symposium on Photon and Beam Scienc

Simulations of plasma channel formation by knife-like nanosecond laser beam

Abstract: The results of the simulations performed in KIAM are presented. Formation of channels in gas targets using a ns-laser is considered in relevant regimes: output energy hundreds of Joules, nanosecond duration laser pulse, from 1 to 10 petawatt main laser pulse power. Such a kind of experiments are planned in the European laser center ELI-Beamline. They will develop a laser induced method of relativistic electrons acceleration, based on ideas investigated previously in NLBL. The magnetohydrodynamic codes NPINCH and MARPLE are used for 1D and 2D simulations of plasma channel formation in the region of elongated focus of knife-like nanosecond laser beam in under-critical gas density. Such plasma channel can be applied for transportation of high power femtosecond laser beams over large distances. The 2D simulations are performed to investigate the process of symmetrization of the channel, when the asymmetry of initial channel is caused by asymmetric deposition of the laser energy due to spatial structure of a plane focus of the laser beam. The simulations show how to reach the regimes of symmetric plasma channel formation. With 1D simulations the parameters of plasma channels for various cases under the condition of channel symmetrization are obtained.Note: Research direction:Mathematical modelling in actual problems of science and technic