Marco Borghesi

Publications (244) View all

• Article: Ion acceleration by superintense laser-plasma interaction

  Andrea Macchi, Marco Borghesi, Matteo Passoni
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  ABSTRACT: Ion acceleration driven by superintense laser pulses is attracting an impressive and steadily increasing effort. Motivations can be found in the potential for a number of foreseen applications and in the perspective to investigate novel regimes as far as available laser intensities will be increasing. Experiments have demonstrated in a wide range of laser and target parameters the generation of multi-MeV proton and ion beams with unique properties such as ultrashort duration, high brilliance and low emittance. In this paper we give an overview of the state-of-the art of ion acceleration by laser pulses as well as an outlook on its future development and perspectives. We describe the main features observed in the experiments, the observed scaling with laser and plasma parameters and the main models used both to interpret experimental data and to suggest new research directions.
  02/2013;
• Article: Simulation of relativistically colliding laser-generated electron flows

  Xiaohu Yang, Mark E. Dieckmann, Gianluca Sarri, Marco Borghesi
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  ABSTRACT: The plasma dynamics resulting from the simultaneous impact, of two equal, ultra-intense laser pulses, in two spatially separated spots, onto a dense target is studied via particle-in-cell (PIC) simulations. The simulations show that electrons accelerated to relativistic speeds, cross the target and exit at its rear surface. Most energetic electrons are bound to the rear surface by the ambipolar electric field and expand along it. Their current is closed by a return current in the target, and this current configuration generates strong surface magnetic fields. The two electron sheaths collide at the midplane between the laser impact points. The magnetic repulsion between the counter-streaming electron beams separates them along the surface normal direction, before they can thermalize through other beam instabilities. This magnetic repulsion is also the driving mechanism for the beam-Weibel (filamentation) instability, which is thought to be responsible for magnetic field growth close to the internal shocks of gamma-ray burst (GRB) jets. The relative strength of this repulsion compared to the competing electrostatic interactions, which is evidenced by the simulations, suggests that the filamentation instability can be examined in an experimental setting.
  11/2012;
• Article: Magnetic instability in a dilute circular rarefaction wave

  Mark Eric Dieckmann, Gianluca Sarri, Marco Borghesi
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  ABSTRACT: The generation of a magnetic field in a circular rarefaction wave is examined in form of a 2D particle-in-cell (PIC) simulation. Electrons with a temperature of 32 keV are uniformly distributed within a cloud with a radius of 14.2 electron skin depths. They expand under their thermal pressure and carry with them the cold protons, which are initially concentrated in a hollow ring at the boundary of the electron cloud. The interior of the ring contains an immobile positive charge background that compensates for the electron charge. The protons expand in form of a circularly symmetric rarefaction wave and they extract energy from the electrons. A thermal anisotropy of the electrons develops and triggers through a Weibel-type instability the growth of TM waves within the plasma cloud, which acts as a wave guide. The changing cross section of this waveguide introduces a coupling between the TM wave and a TE wave and in-plane magnetic fields grow. The relevance of the simulation results to a previous experimental study of a laser-ablated wire is discussed.
  11/2012;
• Article: Particle simulation study of electron heating by counterstreaming ion beams ahead of supernova remnant shocks

  M. E. Dieckmann, A. Bret, G. Sarri, E. Perez Alvaro, I. Kourakis, M. Borghesi
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  ABSTRACT: The growth and saturation of Buneman-type instabilities is examined with a particle-in-cell (PIC) simulation for parameters that are representative for the foreshock region of fast supernova remnant (SNR) shocks. A dense ion beam and the electrons correspond to the upstream plasma and a fast ion beam to the shock-reflected ions. The purpose of the 2D simulation is to identify the nonlinear saturation mechanisms, the electron heating and potential secondary instabilities that arise from anisotropic electron heating and result in the growth of magnetic fields. We confirm that the instabilities between both ion beams and the electrons saturate by the formation of phase space holes by the beam-aligned modes. The slower oblique modes accelerate some electrons, but they can not heat up the electrons significantly before they are trapped by the faster beam-aligned modes. Two circular electron velocity distributions develop, which are centred around the velocity of each ion beam. They develop due to the scattering of the electrons by the electrostatic wave potentials. The growth of magnetic fields is observed, but their amplitude remains low.
  06/2012;
• Source

  Available from: Alexey S Boldarev

  Article: Ionography of nanostructures with the use of a laser plasma of cluster targets

  A. Ya. Faenov, T. A. Pikuz, Y. Fukuda, M. Kando, H. Kotaki, T. Homma, K. Kawase, T. Kameshima, A. Pirozhkov, A. Yogo, [......], A. S. Boldarev, V. A. Gasilov, A. I. Magunov, S. Kar, M. Borghesi, P. Bolton, H. Daido, T. Tajima, I. Kato, S. V. Bulanov
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  ABSTRACT: It has been shown that a femtosecond plasma of cluster targets is an almost isotropic source of fast ions and, hence, can be used to obtain ionographic images with a wide field of view. The spatial resolution of the resulting ionographic images is no worse than 600 nm, which corresponds to a uniquely high value of about 105 of the ratio of the field of view to the resolution. The use of 100–300-keV ion fluxes ensures the sensitivity of the method to the sample thickness of no worse than 100 nm even for samples consisting of light chemical elements (C, H). The proposed method can be used to obtain images of low-contrast biological objects, thin films, membranes, and other nanostructured objects.
  JETP Letters 04/2012; 89(10):485-491. · 1.35 Impact Factor