Vasily Seredov

Heinrich-Heine-Universität Düsseldorf, Düsseldorf, North Rhine-Westphalia, Germany

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Publications (6)15.68 Total impact

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    ABSTRACT: We present a theory for electron self-injection in nonlinear, multidimensional plasma waves excited by a short laser pulse in the bubble regime or by a short electron beam in the blowout regime. In these regimes, which are typical for electron acceleration in the last impressive experiments, the laser radiation pressure or the electron beam charge pushes out plasma electrons from some region, forming a plasma cavity or a bubble with a huge ion charge. The plasma electrons can be trapped in the bubble and accelerated by the plasma wakefields up to a very high energy. We derive the condition of the electron trapping in the bubble. The developed theory predicts the trapping cross section in terms of the bubble radius and the bubble velocity. It is found that the dynamic bubble deformations observed in the three-dimensional (3D) particle-in-cell (PIC) simulations influence the trapping process significantly. The bubble elongation reduces the gamma-factor of the bubble, thereby strongly enhancing self-injection. The obtained analytical results are in good agreement with the 3D PIC simulations.
    New Journal of Physics 04/2010; 12(4):045009. DOI:10.1088/1367-2630/12/4/045009 · 3.67 Impact Factor
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    ABSTRACT: We present a simple model (piecewise model) for electron self-injection in nonlinear, multidimensional plasma waves excited by short laser pulse in the bubble regime. In this model fields are assumed to be constant in quarters that yields an extra integral of the electron motion and allows us to obtain analytical expressions for the electron trajectories. In the framework of this model we derive the condition of the electron trapping in the bubble. The developed theory predicts the trapping cross section in terms of the bubble radius and the bubble velocity and reveals key features of electron trapping in three-dimensional regime.
    04/2010; DOI:10.1063/1.3426075
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    ABSTRACT: We present an analytical model for electron self-injection in a nonlinear, multidimensional plasma wave excited by a short laser pulse in the bubble regime or by a short electron beam in the blowout regime. In these regimes, which are typical for electron acceleration, the laser radiation pressure or the electron beam charge pushes out background plasma electrons forming a plasma cavity--bubble--with a huge ion charge. The plasma electrons can be trapped in the bubble and accelerated by the plasma wakefields up to very high energies. The model predicts the condition for electron trapping and the trapping cross section in terms of the bubble radius and the bubble velocity. The obtained results are in a good agreement with results of 3D particle-in-cell simulations.
    Physical Review Letters 10/2009; 103(17):175003. DOI:10.1103/PHYSREVLETT.103.175003 · 7.51 Impact Factor
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    ABSTRACT: In relativistic laser plasma interaction, electrons can be simultaneously accelerated and wiggled in an ion cavity created in the wake of an intense short pulse laser propagating in an underdense plasma. As a consequence of their motion, the accelerated electrons emit an intense x-ray beam called laser produced betatron radiation. Being an emission from charged particles, the features of the betatron source are directly linked to the electrons trajectories. In particular, the radiation is emitted in the direction of the electrons velocity. In this article we show how an image of electrons orbits in the wakefield cavity can be deduced from the structure of x-ray spatial profiles.
    Physics of Plasmas 07/2008; 15(7). DOI:10.1063/1.2952831 · 2.25 Impact Factor
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    ABSTRACT: This Letter aims to demonstrate the ultrafast nature of laser produced betatron radiation and its potential for application experiments. An upper estimate of the betatron x-ray pulse duration has been obtained by performing a time-resolved x-ray diffraction experiment: The ultrafast nonthermal melting of a semiconductor crystal (InSb) has been used to trigger the betatron x-ray beam diffracted from the surface. An x-ray pulse duration of less than 1 ps at full width half-maximum (FWHM) has been measured with a best fit obtained for 100 fs FWHM.
    Physics of Plasmas 07/2007; 14(8):080701-080701-4. DOI:10.1063/1.2754624 · 2.25 Impact Factor
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    Vasily Seredov
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    ABSTRACT: The acceleration of charged particles is one of the fundamental problems in high energy physics. The conventional accelerator technology has nearly reached its natural limit because the maximum available electric field is bounded by destruction of the accelerating structures. This fundamental limit on the electric field leads to the monstrous sizes of the modern accelerators. The main advantage of plasma based accelerators is the possibility to increase the electric field and consequently the accelerating rate by several orders of magnitude compared to the conventional technology. One of the most promising ways to employ the plasma acceleration is to use high intensity ultra-short laser pulses to excite the plasma wake field. The physics of relativistic laser plasma is highly nonlinear and requires extensive multi-dimensional computer simulations. The present work is dedicated mainly to the problem of electron acceleration in the so-called "bubble" regime. The advantage of the bubble regime is the possibility to generate quasi-monoenergetic electron bunches. The bubble regime was first discovered in three dimensional particle-in-cell (PIC) simulations. Recently, it was observed in a number of laser-plasma experiments. One of the central questions in the physics of the bubble is the problem of particle trapping and trajectories of the relativistic electrons during the acceleration stage. Because the bubble structure has not only the longitudinal - accelerating - electric field, but also transverse fields, the electrons runs at curved trajectories and emit strong betatron radiation in x-ray range. The angular distribution of these x-rays allows to draw conclusions on the particle trajectories. In this work, a simplified analytic description of particle trajectories in the bubble fields is suggested. Further, the bubble is simulated using the 3D PIC code VLPL (Virtual Laser Plasma Laboratory). The code VLPL has been further developed to allow individual marking for each particle. Thus, trajectories of individual particles trapped in the bubble can be traced over the full interaction length. A simulation done for realistic laser-plasma parameters has shown a reasonable agreement between the simplified theory and the simulations. It is shown that in some cases the electron trajectories have the form of a helix around the axis of the laser pulse propagation. In addition, we have stored initial positions of all the trapped particles. This analysis revealed that the electron trapping in the bubble is not steady, but rather contains striations. We have discussed the capture of electrons in the bubble for linear and circular polarization cases. It was shown that the shape of the area of electrons capture directly depends on the laser pulse polarization. Finally, the new analytic model for an ultra-short laser beam has been developed. Although there is a well-known model for an infinite focused laser pulse, it becomes inexact when applied to an ultra-short laser. The reason is that the ultra-short pulse contains many frequencies. The analytic model has been implemented in the VLPL3D code and used to study dependence of electron acceleration by an ultra-short laser pulse as a function of the focal position in plasma.