Characteristics of relativistic electron mirrors generated by an ultrashort nonadiabatic laser pulse from a nanofilm.

Kulagin, Victor V,Cherepenin, Vladimir A,Gulyaev, Yuri V,Kornienko, Vladimir N,Pae, Ki Hong,Valuev, Victor V,Lee, Jongmin,Suk, Hyyong Published by the American Physical Society through 2009 Physical review. E, Statistical, nonlinear, and so Vol.80 No.1

<P>For controllable generation of an isolated attosecond relativistic electron bunch [relativistic electron mirror (REM)] with nearly solid-state density, we proposed [V. V. Kulagin, Phys. Rev. Lett. 99, 124801 (2007)] to use a solid nanofilm illuminated normally by an ultraintense femtosecond laser pulse having a sharp rising edge (nonadiabatic laser pulse). In this paper, the REM characteristics are investigated in a regular way for a wide range of parameters. With the help of two-dimensional (2D) particle-in-cell (PIC) simulations, it is shown that, in spite of Coulomb forces, all of the electrons in the laser spot can be synchronously accelerated to ultrarelativistic velocities by the first half-cycle of the field, which has large enough amplitude. For the process of the REM generation, we also verify a self-consistent one-dimensional theory, which we developed earlier (cited above) and which takes into account Coulomb forces, radiation of the electrons, and laser amplitude depletion. This theory shows a good agreement with the results of the 2D PIC simulations. Finally, the scaling of the REM dynamical parameters with the field amplitude and the nanofilm thickness is analyzed.</P>

Generation of intense coherent attosecond X-ray pulses using relativistic electron mirrors

Kulagin, V V,Kornienko, V N,Cherepenin, Vladimir A,Suk, Hyyong Turpion 2013 Quantum electronics Vol.43 No.5

Cross Flow During Twist Extrusion: Theory, Experiment, and Application

Kulagin, R.,Latypov, M. I.,Kim, H. S.,Varyukhin, V.,Beygelzimer, Y. Springer Science + Business Media 2013 Metallurgical and materials transactions. A, Physi Vol.44 No.7

Formation of relativistic electron mirrors in laser-plasma

Victor V. Kulagin,Hyyong Suk 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.52

The generation of relativistic electron mirrors (bunches with extremely short lengths) in laserplasma interactions is considered. It is shown that such a mirror can be generated by using an ultra-intense nonadiabatic laser pulse (pulse with a sharp rising edge) incident normally upon a thin plasma layer. Due to the relativistic contraction, the resulting length of the electron mirror can be considerably smaller than the initial thickness of the plasma layer. The lifetime of the relativistic mirror depends on the dimensionless amplitude and shape of the laser pulse, the initial density of electrons, and the thickness of the plasma layer. As a result, relativistic electron mirrors can survive during the rst several half-periods of an external electromagnetic eld, which can correspond to time intervals of hundreds of femtoseconds in the laboratory frame.

Attosecond Relativistic Electron Beam by Using an Ultrashort Laser Pulse and a Thin Plasma Layer

Victor V. Kulagin,석희용,허민섭 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.I

Attosecond ($10^{-15}$ s) electron beams will have some important applications in physics, chemistry, material science, {\it etc.}, where ultrafast phenomena play an important role. Hence, how to generate such ultrashort electron beams is an important issue. Here, we propose to use a thin plasma layer illuminated normally by an ultra-intense femtosecond laser pulse having a sharp rising edge (rising time $\sim$ laser oscillation period). In this process, the plasma layer is compressed nonadabatically by the laser pulse, and all electrons are synchronously accelerated to ultra-relativistic velocities by several half-cycles of the laser field. In an experiment, a solid nanofilm, a taped electron beam, or a thin gas jet can be used as possible targets. For these types of targets, we show the generation of an attosecond high-energy electron beam by using particle-in-cell (PIC) simulations.

Bunching of Electron Beams by Ultra-Relativistic Laser Pulses

Victor V. Kulagin,석희용,허민섭,Vladimir A. Cherepenin 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.4

The bunching of an electron beam by an ultra-relativistic laser pulse in vacuum is considered. The one-dimensional theory describing this process is elaborated. The laser pulse is shown to compress the electron beam and to generate fast density modulations (microbunching) in it. Two spatial harmonics can be present simultaneously in longitudinal density modulations of the electron beam - one with the laser wavelength and the other with half of the laser wavelength, and the ratio of the amplitudes of the harmonics depends on the duration of the laser pulse front. The average density of the electron beam (slow density modulation) can be controlled by changing the form of the laser pulse envelope. The number of microbunches in the compressed electron beam can be changed by varying the amplitude of the laser pulse and the initial length of the electron beam, and for certain conditions, only one electron bunch with an attosecond length can be produced. The results of the theory are compared with 1D PIC (Particle-In-Cell) simulations, and a good agreement is found.O?

Generating nearly single-cycle pulses with increased intensity and strongly asymmetric pulses of petawatt level.

Nam, Inhyuk,Kulagin, Victor V,Hur, Min Sup,Lee, In Won,Suk, Hyyong Published by the American Physical Society through 2012 Physical review. E, Statistical, nonlinear, and so Vol.85 No.2

<P>Generation of petawatt-class pulses with a nearly single-cycle duration or with a strongly asymmetric longitudinal profile using a thin plasma layer are investigated via particle-in-cell simulations and the analytical flying mirror model. It is shown that the transmitted pulses having a duration as short as about 4 fs (1.2 laser cycles) or one-cycle front (tail) asymmetric pulses with peak intensity of about 10^{21}W/cm^{2} can be produced by optimizing system parameters. Here, a new effect is found for the shaping of linearly polarized laser pulses, owing to which the peak amplitude of the transmitted pulse becomes larger than that of the incoming pulse, and intense harmonics are generated. Characteristics of the transmitting window are then studied for different parameters of laser pulse and plasma layer. For a circular polarization, it is shown that the flying mirror model developed for shaping laser pulses with ultrathin foils can be successfully applied to plasma layers having a thickness of about the laser wavelength, which allows the shape of the transmitted pulse to be analytically predicted.</P>

Off-Axis Twist Extrusion for Uniform Processing of Round Bars

Yan Beygelzimer,Roman Kulagin,Marat I. Latypov,Viktor Varyukhin,김형섭 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.4

The present paper introduces a twist extrusion (TE) process capable of processing of round bars with uniform deformation and reports physical, analytical, and numerical modeling of the process. It is shown that the ability to treat round bars can be achieved by design of special off-axis TE dies in which the axis of the twist surface is displaced from the central axis of the bar being processed. Physical modeling conducted in the current study with plasticine demonstrates the feasibility of off-axis TE. A marker insert technique employed in the physical model reveals that tool-controlled flow (ideal helical flow) of the material is dominant in the process. Analytical model developed in the present study explains why using off-axis TE dies leads to uniform deformation and how this deformation uniformity depends on the die geometry. The main conclusions made upon analytical modeling are confirmed with complement finite element simulations. The simulations also show that the main deformation mode in off-axis TE is simple shear at the intersection planes between the twist and the straight channels of the die. The present paper introduces a twist extrusion (TE) process capable of processing of round bars with uniform deformation and reports physical, analytical, and numerical modeling of the process. It is shown that the ability to treat round bars can be achieved by design of special off-axis TE dies in which the axis of the twist surface is displaced from the central axis of the bar being processed. Physical modeling conducted in the current study with plasticine demonstrates the feasibility of off-axis TE. A marker insert technique employed in the physical model reveals that tool-controlled flow (ideal helical flow) of the material is dominant in the process. Analytical model developed in the present study explains why using off-axis TE dies leads to uniform deformation and how this deformation uniformity depends on the die geometry. The main conclusions made upon analytical modeling are confirmed with complement finite element simulations. The simulations also show that the main deformation mode in off-axis TE is simple shear at the intersection planes between the twist and the straight channels of the die. The simulations also show that the main deformation mode in off-axis TE is simple shear at the intersection planes between the twist and the straight channels of the die.

Poster Session : PS 0144 ; Neurology : Estimating Effi cacy of Active Hexose Correlated Compound as Immune Therapy for Patients Diagnosed with Pharmacoresistant Epilepsy

( Natalia Mikhilichenko ),( Viacheslav Kulagin ) 대한내과학회 2014 대한내과학회 추계학술대회 Vol.2014 No.1

Background: examination of clinical neuroimmune disorders of patients diagnosed with pharmacoresistant epilepsy, to estimate immune role in pathogenesis of the disease and effi cacy of immune therapy, Active Hexose Correlated Compound (AHCC) supplement, in particular. Methods: several children with unmoderate verifi ed resistant epilepsy were examined with clinico-paraclinic Methods: Immunologic methods included prelaboratory examination aimed at revealing clinical syndromes of secondary immunodefi ciency and laboratory examination with the purpose to identify multiple defects in the immune system. Immunologic examination was performed according to standard Methods: In order to determine immune status there were measured quantitative and functional indicators: 1) percentage of T- and B- lymphocytes in peripheral blood (total number of lymphocytes, percentage and absolute number of mature T-cells - CD3+, two basic subpopulations - helpers CD4+ and killers-suppressors CD8+; В-lymphocytes - CD20+; immunoregulatory balance - balance between CD4+ and CD8+; 2) concentration of serum immunoglobulin А, G, М (IgА, IgG, IgМ). All patients received combined treatment including baseline antiepileptic and immune therapy АНСС -2 i.d. during one month. Results: after AHCC intake patients had positive quantity changes of peripheral t-cell pool (CD3+), Т-helpers amount increase (CD4+) and 1,4 times more increase of T-suppressors/ killers (CD8+-lymphocytes). Due to CD4+ lymphocytes subset, current changes moved up immunoregulatory balance (CD4+/CD8+). 35% of clinical changes displayed frequency and intensity reduction of epileptic seizures, other patients had somatic health status and physiological functions improved. Conclusions: Mentioned before data demonstrate that patients with resistant epilepsy have signifi cant neuroimmune disorders. АНСС Immunotherapy improves immune status by increasing amount of Т-lymphocytes, regulate subset balance, activates phagocytes and humoral function. In addition, it decreases neuroimmunization by regulating amount of serum immunoglobulins. Such effect indicates reverse of autoimmune process which has pathobiological signifi cance in epileptogenesis.

Terahertz radiation emission from plasma beat-wave interactions with a relativistic electron beam

Gupta, D.N.,Kulagin, V.V.,Suk, H. North-Holland Pub. Co 2017 OPTICS COMMUNICATIONS - Vol.401 No.-

We present a mechanism to generate terahertz radiation from laser-driven plasma beat-wave interacting with an electron beam. The theory of the energy transfer between the plasma beat-wave and terahertz radiation is elaborated through nonlinear coupling in the presence of a negative-energy relativistic electron beam. An expression of terahertz radiation field is obtained to find out the efficiency of the process. Our results show that the efficiency of terahertz radiation emission is strongly sensitive to the electron beam energy. Emitted field strength of the terahertz radiation is calculated as a function of electron beam velocity.