Excitation of Accelerating Plasma Waves by Counter-Propagating Laser Beams

Technical Report · Fri Apr 05 04:00:00 EST 2002

OSTI ID:796223

Shvets, Gennady ^[1]; Fisch, Nathaniel J; Pukhov, Alexander

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1. Princeton Plasma Physics Laboratory

The conventional approach to exciting high phase velocity waves in plasmas is to employ a laser pulse moving in the direction of the desired particle acceleration. Photon downshifting then causes momentum transfer to the plasma and wave excitation. Novel approaches to plasma wake excitation, colliding-beam accelerator (CBA), which involve photon exchange between the long and short counter-propagating laser beams, are described. Depending on the frequency detuning Dw between beams and duration tL of the short pulse, there are two approaches to CBA. The first approach assumes tL ª 2/wp. Photons exchanged between the beams deposit their recoil momentum in the plasma driving the plasma wake. Frequency detuning between the beams determines the direction of the photon exchange, thereby controlling the phase of the plasma wake. This phase control can be used for reversing the slippage of the accelerated particles with respect to the wake. A variation on the same theme, super-beatwave accelerator, is also described. In the second approach, a short pulse with tL >> 2/wp1 detuned by Dw ~ 2wp from the counter-propagating beam is employed. While parametric excitation of plasma waves by the electromagnetic beatwave at 2wp of two co-propagating lasers was first predicted by Rosenbluth and Liu [M.N. Rosenbluth, C.S. Liu, Phys. Rev. Lett. 29 (1972) 701], it is demonstrated that the two excitation beams can be counter-propagating. The advantages of using this geometry (higher instability growth rate, insensitivity to plasma inhomogeneity) are explained, and supporting numerical simulations presented.

• Research Organization: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ
• Sponsoring Organization: USDOE Office of Science
• DOE Contract Number: AC02-76CH03073
• OSTI ID: 796223
• Report Number(s): PPPL-3684.pdf
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY