SELF-GENERATED AXIAL MAGNETIC-FIELD IN LASER-PRODUCED PLASMAS

Self generated axial magnetic field due to ponderomotive force in a la ser produced plasmas is discussed. When an intense laser beam propagat es in an expanding plasma, spatial inhomogeneities present in the inte nsity profile of the incident laser beam can grow rapidly due to self- focusing effect, which result in localized filamentation of higher int ensity. This filamentation can directly cause localized heating of the target, thus destroying the uniformity in the ablative acceleration n ecessary for high compression implosions. In view of experimental obse rvations a small fluctuation in the intensity profile of a plane elect romagnetic beam grows as it propagates in the plasma where the self-ge nerated axial magnetic field cannot be neglected. Based on these obser vations we discuss a mechanism of filamentation instability due to pon deromotive forces in laser produced plasmas.