Three Dimensional Relativistic Electromagnetic Sub-cycle Solitons

Three dimensional (3D) relativistic electromagnetic sub-cycle solitons were observed in 3D Particle-in-Cell simulations of an intense short laser pulse propagation in an underdense plasma. Their structure resembles that of an oscillating electric dipole with a poloidal electric field and a toroidal magnetic field that oscillate in-phase with the electron density with frequency below the Langmuir frequency. On the ion time scale the soliton undergoes a Coulomb explosion of its core, resulting in ion acceleration, and then evolves into a slowly expanding quasi-neutral cavity.Comment: 5 pages, 6 figures; http://www.ile.osaka-u.ac.jp/research/TSI/Timur/soliton/index.htm

Radiation Pressure Dominate Regime of Relativistic Ion Acceleration

The electromagnetic radiation pressure becomes dominant in the interaction of the ultra-intense electromagnetic wave with a solid material, thus the wave energy can be transformed efficiently into the energy of ions representing the material and the high density ultra-short relativistic ion beam is generated. This regime can be seen even with present-day technology, when an exawatt laser will be built. As an application, we suggest the laser-driven heavy ion collider.Comment: 10 pages, 4 figure

Laser acceleration of protons from near critical density targets for application to radiation therapy

Laser accelerated protons can be a complimentary source for treatment of oncological diseases to the existing hadron therapy facilities. We demonstrate how the protons, accelerated from near-critical density plasmas by laser pulses having relatively small power, reach energies which may be of interest for medical applications. When an intense laser pulse interacts with near-critical density plasma it makes a channel both in the electron and then in the ion density. The propagation of a laser pulse through such a self-generated channel is connected with the acceleration of electrons in the wake of a laser pulse and generation of strong moving electric and magnetic fields in the propagation channel. Upon exiting the plasma the magnetic field generates a quasi-static electric field that accelerates and collimates ions from a thin filament formed in the propagation channel. Two-dimensional Particle-in-Cell simulations show that a 100 TW laser pulse tightly focused on a near-critical density target is able to accelerate protons up to energy of 250 MeV. Scaling laws and optimal conditions for proton acceleration are established considering the energy depletion of the laser pulse.Comment: 25 pages, 8 figure

Current sheets at three-dimensional magnetic nulls:effect of compressibility

The nature of current sheet formation in the vicinity of three-dimensional (3D) magnetic null points is investigated. The particular focus is upon the effect of the compressibility of the plasma on the qualitative and quantitative properties of the current sheet. An initially potential 3D null is subjected to shearing perturbations, as in a previous paper [Pontin et al., Phys. Plasmas, in press (2007)]. It is found that as the incompressible limit is approached, the collapse of the null point is suppressed, and an approximately planar current sheet aligned to the fan plane is present instead. This is the case regardless of whether the spine or fan of the null is sheared. Both the peak current and peak reconnection rate are reduced. The results have a bearing on previous analytical solutions for steady-state reconnection in incompressible plasmas, implying that fan current sheet solutions are dynamically accessible, while spine current sheet solutions are not.Comment: to appear in Physics of Plasmas. This version contains updated figures and references, additional discussion, and typos are fixed. This is the second in a series of papers - the first of which (by the same authors) is located at astro-ph/0701462. A version with higher quality figures can be found at http://www.maths.dundee.ac.uk/~dpontin

Numerical calculations of a high brilliance synchrotron source and on issues with characterizing strong radiation damping effects in non-linear Thomson/Compton backscattering experiments

A number of theoretical calculations have studied the effect of radiation reaction forces on radiation distributions in strong field counter-propagating electron beam-laser interactions, but could these effects - including quantum corrections - be observed in interactions with realistic bunches and focusing fields, as is hoped in a number of soon to be proposed experiments? We present numerical calculations of the angularly resolved radiation spectrum from an electron bunch with parameters similar to those produced in laser wakefield acceleration experiments, interacting with an intense, ultrashort laser pulse. For our parameters, the effects of radiation damping on the angular distribution and energy distribution of \emph{photons} is not easily discernible for a "realistic" moderate emittance electron beam. However, experiments using such a counter-propagating beam-laser geometry should be able to measure such effects using current laser systems through measurement of the \emph{electron beam} properties. In addition, the brilliance of this source is very high, with peak spectral brilliance exceeding $10^{29}$ photons$\,$s$^{-1}$mm$^{-2}$mrad$^{-2}(0.1$% bandwidth$)^{-1}$ with approximately 2% efficiency and with a peak energy of 10 MeV.Comment: 11 figures, 11 page

Lorentz-Abraham-Dirac vs Landau-Lifshitz radiation friction force in the ultrarelativistic electron interaction with electromagnetic wave (exact solutions)

When the parameters of electron - extreme power laser interaction enter the regime of dominated radiation reaction, the electron dynamics changes qualitatively. The adequate theoretical description of this regime becomes crutially important with the use of the radiation friction force either in the Lorentz-Abraham-Dirac form, which possess unphysical runaway solutions, or in the Landau-Lifshitz form, which is a perturbation valid for relatively low electromagnetic wave amplitude. The goal of the present paper is to find the limits of the Landau-Lifshitz radiation force applicability in terms of the electromagnetic wave amplitude and frequency. For this a class of the exact solutions to the nonlinear problems of charged particle motion in the time-varying electromagnetic field is used.Comment: 14 pages, 5 figure

Complicated colonic diverticular disease-indications and strategies for surgical treatment

Purpose: Colonic diverticular disease is a common disease worldwide. Complicated diverticulitis is determined by presence of perforation, abscess, phlegmon, stricture, obstruction, fistula or hemorrhage. It is an indication for operative management. The aim of the present study was to determine the indications for surgery of complicated diverticular disease, to compare resection with primary anastomosis to Hartmann`s procedure as the optimal urgent operative strategy for patients with complicated acute diverticulitis and to analyze the factors affecting the outcome.Material and methods: Between 1999 and 2012, 250 patients with symptomatic colonic diverticular disease were hospitalized in the Department of General and Hepatopancreatic Surgery, University Hospital Alexandrovska of Sofia. Of them, 39 patients with complicated colonic diverticulitis were surgically treated. Several factors that could influence on the choice of surgical strategy were analyzed by means of SPSS 19.0.1 statistical package.Results: Surgery was applied in 31 patients with perforation, one patient with diverticular bleeding, five patients with fistulas and two patients with bowel obstruction based on diverticular disease.Conclusion: The surgical treatment of complicated diverticular disease, especially of that with peritonitis, remains a challenge. The performance of resection with primary anastomosis with or without protective stoma in selected patients is an alternative to Hartmann`s procedure

Excitation of nonlinear two-dimensional wake waves in radially-nonuniform plasma

It is shown that an undesirable curvature of the wave front of two-dimensional nonlinear wake wave excited in uniform plasma by a relativistic charged bunch or laser pulse may be compensated by radial change of the equilibrium plasma density.Comment: 6 pages, 4 figure