Second harmonic generation and off-axis electrons in the blowout regime of a Laser Wakefield Accelerator

Summary form only given. In the blowout (cavitation) regime of a laser wakefield accelerator, the interaction of the intense laser field with the high density shell of the plasma cavity (bubble) can generate an electro-optic shock of second harmonic at the Cherenkov angle. This radiation pattern is produced under similar conditions as when high energy off-axis electrons were observed. These electrons are of particular interest since they are well suited for external injection into a laser wake fieId acceleration structure. Recent experimental results at the U.S. Naval Research Laboratory, using a 10 TW, 50 fs, Ti- Sapphire laser, have shown the existence of such a second harmonic ring. Characterization of this optical radiation and its relationship to off-axis electrons will be presented.