2018, Alkhimova, M.A., Faenov, A.Ya., Pikuz, T.A., Skobelev, I.Yu., Pikuz, S.A., Nishiuchi, M., Sakaki, H., Pirozhkov, A.S., Sagisaka, S., Dover, N.P., Kondo, Ko., Ogura, K., Fukuda, Y., Kiriyama, H., Esirkepov, T., Bulanov, S V., Andreev, A., Kando, M., Zhidkov, A., Nishitani, K., Miyahara, T., Watanabe, Y., Kodama, R., Kondo, K.

We report about nonlinear growth of x-ray emission intensity emitted from plasma generated by femtosecond petawatt laser pulses irradiating stainless steel foils. X-ray emission intensity increases as ∼ I 4.5 with laser intensity I on a target. High spectrally resolved x-ray emission from front and rear surfaces of 5 μm thickness stainless steel targets were obtained at the wavelength range 1.7-2.1 Å, for the first time in experiments at femtosecond petawatt laser facility J-KAREN-P. Total intensity of front x-ray spectra three times dominates to rear side spectra for maximum laser intensity I ≈ 3.21021 W/cm2. Growth of x-ray emission is mostly determined by contribution of bremsstrahlung radiation that allowed estimating bulk electron plasma temperature for various magnitude of laser intensity on target.

2019, Morace, A., Iwata, N., Sentoku, Y., Mima, K., Arikawa, Y., Yogo, A., Andreev, A., Tosaki, S., Vaisseau, X., Abe, Y., Kojima, S., Sakata, S., Hata, M., Lee, S., Matsuo, K., Kamitsukasa, N., Norimatsu, T., Kawanaka, J., Tokita, S., Miyanaga, N., Shiraga, H., Sakawa, Y., Nakai, M., Nishimura, H., Azechi, H., Fujioka, S., Kodama, R.

Increasing the laser energy absorption into energetic particle beams represents a longstanding quest in intense laser-plasma physics. During the interaction with matter, part of the laser energy is converted into relativistic electron beams, which are the origin of secondary sources of energetic ions, γ-rays and neutrons. Here we experimentally demonstrate that using multiple coherent laser beamlets spatially and temporally overlapped, thus producing an interference pattern in the laser focus, significantly improves the laser energy conversion efficiency into hot electrons, compared to one beam with the same energy and nominal intensity as the four beamlets combined. Two-dimensional particle-in-cell simulations support the experimental results, suggesting that beamlet interference pattern induces a periodical shaping of the critical density, ultimately playing a key-role in enhancing the laser-to-electron energy conversion efficiency. This method is rather insensitive to laser pulse contrast and duration, making this approach robust and suitable to many existing facilities.

2016, Lécz, Z., Konoplev, I.V., Seryi, A., Andreev, A.

This paper proposes a novel and effective method for generating GigaGauss level, solenoidal quasi-static magnetic fields in under-dense plasma using screw-shaped high intensity laser pulses. This method produces large solenoidal fields that move with the driving laser pulse and are collinear with the accelerated electrons. This is in contrast with already known techniques which rely on interactions with over-dense or solid targets and generates radial or toroidal magnetic field localized at the stationary target. The solenoidal field is quasi-stationary in the reference frame of the laser pulse and can be used for guiding electron beams. It can also provide synchrotron radiation beam emittance cooling for laser-plasma accelerated electron and positron beams, opening up novel opportunities for designs of the light sources, free electron lasers, and high energy colliders based on laser plasma acceleration.

2017, Dalimier, E., Ya Faenov, A., Oks, E., Angelo, P., Pikuz, T.A., Fukuda, Y., Andreev, A., Koga, J., Sakaki, H., Kotaki, H., Pirozhkov, A., Hayashi, Y., Skobelev, I.Yu., Pikuz, S.A., Kawachi, T., Kando, M., Kondo, K., Zhidkov, A., Tubman, E., Butler, N.M.H., Dance, R.J., Alkhimova, M.A., Booth, N., Green, J., Gregory, C., McKenna, P., Woolsey, N., Kodama, R.

We present X-ray spectroscopic diagnostics in femto-second laser-driven experiments revealing nonlinear phenomena caused by the strong coupling of the laser radiation with the created plasma. Among those nonlinear phenomena, we found the signatures of the Two Plasmon Decay (TPD) instability in a laser-driven CO2 cluster-based plasma by analyzing the Langmuir dips in the profile of the O VIII Lyϵ line, caused by the Langmuir waves created at the high laser intensity 3 1018Wcm-2. With similar laser intensities, we reveal also the nonlinear phenomenon of the Second Harmonic Generation (SHG) of the laser frequency by analyzing the nonlinear phenomenon of satellites of Lyman δ and ϵ lines of Ar XVII. In the case of relativistic laser-plasma interaction we discovered the Parametric Decay Instability (PDI)-induced ion acoustic turbulence produced simultaneously with Langmuir waves via irradiation of thin Si foils by laser intensities of 1021Wcm-2.

2010, Sokollik, T., Paasch-Colberg, T., Gorling, K., Eichmann, U., Schnürer, M., Steinke, S., Nickles, P.V., Andreev, A., Sandner, W.

We report on our experiments on laser-driven ion acceleration using fully isolated mass-limited spheres with a diameter down to 8μm for the first time. Two-dimensional (2D) particle-in-cell (PIC) and hydro-code simulations were used to show that the pre-plasma at both the front and rear sides of the target strongly affect the efficiency of the ion acceleration. The mechanism of the plasma flow around mass-limited targets has not yet been identified for laser-driven ion acceleration. Our models indicate that this effect is the cause of the observed limitation to the ion-beam energy in both previous experiments and in our own. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

2021, Andreev, A., Platonov, K., Lécz, Z., Hafz, N.

Interaction of circularly polarized laser pulses with spherical nano-droplets generates nanometer-size magnets with lifetime on the order of hundreds of femtoseconds. Such magnetic dipoles are close enough in a cluster target and magnetic interaction takes place. We investigate such system of several magnetic dipoles and describe their rotation in the framework of Lagrangian formalism. The semi-analytical results are compared to particle-in-cell simulations, which confirm the theoretically obtained terrahertz frequency of the dipole oscillation.

2015, Lécz, Z., Andreev, A., Seryi, A.

The efficient transfer of angular orbital momentum from circularly polarized laser pulses into ions of solid density targets is investigated with different geometries using particle-in-cell simulations. The detailed electron and ion dynamics presented focus upon the energy and momentum conversion efficiency. It is found that the momentum transfer is more efficient for spiral targets and the maximum value is obtained when the spiral step is equal to twice the laser wavelength. This study reveals that the angular momentum distribution of ions strongly depends up on the initial target shape and density.

2016, Kawata, S., Kamiyama, D., Ohtake, Y., Takano, M., Barada, D., Kong, Q., Wang, P.X., Gu, Y.J., Wang, W.M., Limpouch, J., Andreev, A., Bulanov, S.V., Sheng, Z.M., Klimo, O., Psikal, J., Ma, Y.Y., Li, X.F., Yu, Q.S.

In this paper a future laser ion accelerator is discussed to make the laser-based ion accelerator compact and controllable. Especially a collimation device is focused in this paper. The future laser ion accelerator should have an ion source, ion collimators, ion beam bunchers, and ion post acceleration devices [Laser Therapy 22, 103(2013)]: the ion particle energy and the ion energy spectrum are controlled to meet requirements for a future compact laser ion accelerator for ion cancer therapy or for other purposes. The energy efficiency from the laser to ions is improved by using a solid target with a fine sub-wavelength structure or a near-critical density gas plasma. The ion beam collimation is performed by holes behind the solid target or a multi-layered solid target. The control of the ion energy spectrum and the ion particle energy, and the ion beam bunching would be successfully realized by a multistage laser-target interaction.