The effect of high intensity laser propagation instabilities on channel formation in underdense plasmas.

Experiments have been performed using high power laser pulses (up to 50 TW) focused into underdense helium plasmas (ne ≤ 5 × 10[sup 19] cm[sup -3]). Using shadowgraphy, it is observed that the laser pulse can produce irregular density channels, which exhibit features such as long wavelength hosing and "sausage-like" self-focusing instabilities. This phenomenon is a high intensity effect and the characteristic period of oscillation of these instabilities is typically found to correspond to the time required for ions to move radially out of the region of highest intensity. [ABSTRACT FROM AUTHOR]