Generation of GeV protons from 1 PW laser interaction with near critical density targets

The propagation of ultra intense laser pulses through matter is connected with the generation of strong moving magnetic fields in the propagation channel as well as the formation of a thin ion filament along the axis of the channel. Upon exiting the plasma the magnetic field displaces the electrons at the back of the target, generating a quasistatic electric field that accelerates and collimates ions from the filament. Two-dimensional Particle-in-Cell simulations show that a 1 PW laser pulse tightly focused on a near-critical density target is able to accelerate protons up to an energy of 1.3 GeV. Scaling laws and optimal conditions for proton acceleration are established considering the energy depletion of the laser pulse.Comment: 26 pages, 8 figure

Accelerating Protons to Therapeutic Energies with Ultra-Intense Ultra-Clean and Ultra-Short Laser Pulses

Proton acceleration by high-intensity laser pulses from ultra-thin foils for hadron therapy is discussed. With the improvement of the laser intensity contrast ratio to 10-11 achieved on Hercules laser at the University of Michigan, it became possible to attain laser-solid interactions at intensities up to 1022 W/cm2 that allows an efficient regime of laser-driven ion acceleration from submicron foils. Particle-In-Cell (PIC) computer simulations of proton acceleration in the Directed Coulomb explosion regime from ultra-thin double-layer (heavy ions / light ions) foils of different thicknesses were performed under the anticipated experimental conditions for Hercules laser with pulse energies from 3 to 15 J, pulse duration of 30 fs at full width half maximum (FWHM), focused to a spot size of 0.8 microns (FWHM). In this regime heavy ions expand predominantly in the direction of laser pulse propagation enhancing the longitudinal charge separation electric field that accelerates light ions. The dependence of the maximum proton energy on the foil thickness has been found and the laser pulse characteristics have been matched with the thickness of the target to ensure the most efficient acceleration. Moreover the proton spectrum demonstrates a peaked structure at high energies, which is required for radiation therapy. 2D PIC simulations show that a 150-500 TW laser pulse is able to accelerate protons up to 100-220 MeV energies.Comment: 26 pages, 6 figure

War, Peace and Social Institutions in Eighteenth-Century British Philosophy

This paper is devoted to the problems of war, peace and social institutions in 18th-century British philosophy. I will not go into details concerning the nature or the history of the social institutions such as those of the wars, but will limit myself only to some concise remarks. My task is much more modest and consists in analysing the correlation and the interdependence of the phenomena mentioned as these problems were understood by British thinkers of the 18th century. I would like also t..

Effects of ionization in a laser Wakefield accelerator

Experimental results are presented from studies of the ionization injection process in laser wakefield acceleration using the Hercules laser with laser power up to 100 TW. Gas jet targets consisting of gas mixtures reduced the density threshold required for electron injection and increased the maximum beam charge. Gas mixture targets produced smooth beams even at densities which would produce severe beam breakup in pure He targets and the divergence was found to increase with gas mixture pressure

Effects of ionization in a laser Wakefield accelerator

Experimental results are presented from studies of the ionization injection process in laser wakefield acceleration using the Hercules laser with laser power up to 100 TW. Gas jet targets consisting of gas mixtures reduced the density threshold required for electron injection and increased the maximum beam charge. Gas mixture targets produced smooth beams even at densities which would produce severe beam breakup in pure He targets and the divergence was found to increase with gas mixture pressure

Guerres et paix

En cent-quarante ans, de 1660 à 1800, la Grande-Bretagne a été en guerre pendant quatre-vingt six ans. Les deux tomes de cet ouvrage étudient les conséquences de cet état de fait sur la société, la vie et les arts. Le premier tome rassemble, outre une préface par Paul-Gabriel Boucé, quatorze articles. Ils analysent, sur l'horizon des lumières britanniques et européennes, les composantes historiques et sociales du phénomène (première partie : « Hommes, conflits, événements ») et l’émergence de concepts nouveaux (deuxième partie : « Guerres et Paix : Histoire des idées et idées de l’Histoire »). Le second tome de Guerres et paix examine les avatars littéraires de la dynamique dialectique engendrée par l’alternance de la guerre et de la paix. Defoe, Pope, Swift, Gay, Lillo, Haendel, Smollett, Sterne, Johnson, Cowper, Ann Radcliffe, Jane Austen apparaissent sous un jour nouveau. C’est l’occasion de bousculer un certain nombre de clichés, parfois encore solidement ancrés dans la critique contemporaine.Pour Hélène, qui comme toujours a été largement mise à contribution. PG