Enhanced Raman forward scattering

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Abstract
Recent experiments on laser wake-field acceleration have indicated a dramatically enhanced value of the accelerating field created through the process of the Raman forward scattering instability. However, the use of the Raman forward scattering instability can be improved. If the initial growth of the instability is from noise, its evolution has problems of reproducibility and is unpredictable in both time and space. We suggest the addition of a small amount of one of the scattered products to the laser pulse or plasma as a seed. This allows the instability to grow from a known and controllable source, giving predictable and reproducible results. Additionally, simulations show that the final wake field and pulse modulation occur much faster and are cleaner with a seed than without. Seeding is especially important when we are operating in the low plasma density or low laser pulse intensity regime. We discuss methods to produce a seed and applications for the production of short laser pulses and electron bunches by this process. © 1996 The American Physical Society.