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Abstract:

The Vulvan Nd:glass laser at the Central Laser Facility (CLF) has recently been upgraded to the Petawatt level (1015 Watts). The three year upgrade project was contracted to deliver 500 J in a near diffraction limited pulse of 500 fs duration. The Petawatt facility will deliver an irradiance on target of 1021 W.cm-2 for a wide ranging experimental programme in fundamental physics and advanced applications. This includes the interaction of super-high intensity light with matter, fast ignition fusion research, photon induced nuclear reactions, electron and ion acceleration by light waves and the exploration of the exotic world of plasma physics dominated by relativity. Of particular relevance to high speed photography, the Petawatt beam will be used to create a source for advanced high-speed imaging using protons, neutrons and X-rays on an hitherto inaccessible time-scale.

Abstract:

We report the first systematic observations of relativistic self-phase-modulation (RSPM) due to the interaction of a high intensity laser pulse with plasma. The plasma was produced in front of a solid target by the prepulse of a 100 TW laser beam. RSPM was observed by monitoring the spectrum of the harmonics generated by the intense laser pulse during the interaction. The multipeaked broadened spectral structure produced by RSPM was studied in plasmas with different density scale lengths for laser interactions at intensities up to 3.0×[formula presented] [formula presented] [formula presented] The results are compared with calculated spectra and agreement is obtained. © 2002 The American Physical Society.