Stimulated Brillouin backscattering (B-SBS) from delayed interaction with a preformed, long scale-length expanding plasma was experimentally investigated in a regime favorable to strong self-focusing (SF) and filamentation. An extremely low backscattering reflectivity (of the order of 10-4) was measured and anomalous time-resolved spectra were observed. Spectral and temporal features of the reflectivity suggest a strong effect of SF on B-SBS: In the early phase of the interaction SF lowers the B-SBS threshold and possibly leads to rapid saturation, while in the late phase there is a substantial decoupling of the SBS active regions from the plasma bulk due to their motion towards the laser beam. This motion is attributed to a moving focus effect driven by ponderomotive SF.
Giulietti, A., Macchi, A., Schifano, E., Biancalana, V., Danson, C., Giulietti, D., et al. (1999). Stimulated Brillouin backscattering from underdense expanding plasmas in a regime of strong filamentation. PHYSICAL REVIEW E, 59(1), 1038-1046 [10.1103/PhysRevE.59.1038].
Stimulated Brillouin backscattering from underdense expanding plasmas in a regime of strong filamentation
Biancalana, V.;
1999-01-01
Abstract
Stimulated Brillouin backscattering (B-SBS) from delayed interaction with a preformed, long scale-length expanding plasma was experimentally investigated in a regime favorable to strong self-focusing (SF) and filamentation. An extremely low backscattering reflectivity (of the order of 10-4) was measured and anomalous time-resolved spectra were observed. Spectral and temporal features of the reflectivity suggest a strong effect of SF on B-SBS: In the early phase of the interaction SF lowers the B-SBS threshold and possibly leads to rapid saturation, while in the late phase there is a substantial decoupling of the SBS active regions from the plasma bulk due to their motion towards the laser beam. This motion is attributed to a moving focus effect driven by ponderomotive SF.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/11365/45375
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