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:	Dr.
Last Name:	Davies
First Name:	Jonathan
E-Mail:	jrdist.utl.pt
Affiliation for Badge:	IST, Lisboa
Institute:	GoLP, Instituto Superior Técnico
Address (Street):	Av. Rovisco Pais
Postal Code, City:	1049-001 Lisboa
Country:	Portugal
Phone:	+351 218419334
Fax:	+351 218464455
Author(s):	J. R. Davies, M. Fajardo
Institute(s):	GoLP, IST
Title:	Magnetic field driven filamentation in laser ablation of solids
Abstract:	Results from magnetohydrodynamic modeling of laser ablation of solids, for intensities of the order of $10^{18}$ W m$^{-2}$ ($10^{14}$ W cm$^{-2}$) and durations of the order of a nanosecond, are reported that show filamentation in the density and magnetic field, in agreement with recent experimental results from PALS and LLE Rochester. The filamentation occured after the growth of the magnetic field and at low densities. Diffusion of the magnetic field generated near the critical surface into cold, sub-critical plasma led to a magnetic pressure comparable to the thermal pressure and to a cyclotron frequency significantly exceeding the collision frequency. The origin of the instability is attributed to density perturbations perpendicular to a temperature gradient, in the presence of an existing magnetic field. A dispersion relations is derived from a simplified set of single fluid equations that gives good qualitative agreement with the code. It provides simple, dimensionless parameters that indicate when the instability will be important, which indicate that it should be a typical feature of laser ablation for time scales greater than $0.1$ ns