Interaction of Short Petawatt Laser Pulses with Plasma
- Theory and Simulations

Laserlab Europe Workshop

Georg-Christoph-Lichtenberg-Haus, Darmstadt
October 14 - 17, 2007 -
Registered Participants Information

Title:	Prof.
Last Name:	Mora
First Name:	Patrick
E-Mail:	Patrick.Moracpht.polytechnique.fr
Affiliation for Badge:	CPHT, Ecole Polytechnique
Institute:	CNRS - Ecole polytechnique
Address (Street):	Route de Saclay
Postal Code, City:	91128 Palaiseau
Country:	France
Phone:	33 1 69 33 42 09
Fax:
Author(s):	P. Mora, T. Grismayer, J.-C. Adam, A. Héron
Institute(s):	Centre de Physique Théorique, Ecole Polytechnique, 91128 Palaiseau Cedex, France
Title:	Electron kinetic effects in the plasma expansion into a vacuum and ion acceleration
Abstract:	Laser created plasma expansion into a vacuum leads to energetic ions which present a strong interest for various applications such as hadron (proton) therapy, proton imaging, nuclear physics, ion accelerators, fast ignition, etc. In the case of ultra-high intensity lasers interacting with thin foils, the laser energy is absorbed by suprathermal electrons which acquire relativistic energies. These electrons invade the foil and cause its expansion, by progressively transferring their energy to the ions. The corresponding electron cooling does not normally preserve the shape of the electron distribution function, and the use of a Boltzmann law with a time dependent temperature is not usually justified. In the present work we analyze the evolution of the electron distribution function during the expansion with a standard Particle-In-Cell code, and with an hybrid code where ions are treated as particles and electrons are described by a distribution function which adiabatically evolves in the slowly varying electric potential, as described by Gurevich [1], both species being coupled by the Poisson equation. We then compare with simpler models using the Boltzmann law, such as the one used in Ref. [2]. We show that the intermediate energy electrons cool down more efficiently than both low energy and high energy electrons. We discuss the effect on the ion acceleration itself and on the structure of the ion front at the plasma-vacuum interface. [1] A. V. Gurevich, Sov. Phys. JETP 26, 575 (1968). [2] P. Mora, Phys Rev E 72, 056401 (2005); Phys. Plasmas 12, 112102 (2005).