Energy transfer between laser beams crossing in ignition hohlraums

The full scale modeling of power transfer between laser beams crossing in plasmas is presented. A new model was developed, allowing calculations of the propagation and coupling of pairs of laser beams with their associated plasma wave in three dimensions. The complete set of laser beam smoothing techniques used in ignition experiments is modeled and their effects on crossed-beam energy transfer are investigated. A shift in wavelength between the beams can move the instability in or out of resonance and hence allows tuning of the energy transfer. The effects of energy transfer on the effective beam pointing and on symmetry have been investigated. Several ignition designs have been analyzed and compared, indicating that a wavelength shift of up to 2 A between cones of beams should be sufficient to control energy transfer in ignition experiments.

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