Stimulated Brillouin backscattering from underdense expanding plasmas in a regime of strong filamentation

Year: 1999

Authors: Giulietti A., Macchi A., Schifano E., Biancalana V., Danson C., Giulietti D., Gizzi LA., Willi O.

Autors Affiliation: CNR, Ist Fis Atom & Mol, I-56127 Pisa, Italy;
Scuola Normale Super Pisa, Pisa, Italy;
Univ Pisa, Ist Nazl Fis Mat, Sez A, Pisa, Italy;
Univ Siena, Dipartimento Fis, I-53100 Siena, Italy;
Rutherford Appleton Lab, Cent Laser Facil, Chilton, England;
Univ Pisa, Dipartimento Fis, Pisa, Italy;
Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London, England

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.


Volume: 59 (1)      Pages from: 1038  to: 1046

KeyWords: laser hot-spots; scattering; light; propagation; waves
DOI: 10.1103/PhysRevE.59.1038

Citations: 22
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