Abstract
Direct-drive inertial Confinement fusion (TCF) requires extremely uniform beams to suppress unwanted hydrodynamic and plasma instabilities. Uniform beams are generated by using random phase plates (RPP)1 to convert long wavelength inhomogeneities into small scale length speckle and by smoothing out the speckle by rapidly moving it in time using spectral bandwidth and dispersion.2 RPPs were developed at the University of Osaka1 and are now routinely used in many of the ICF facilities worldwide.1,3 We have implemented beam smoothing on one arm of the Nova beam for investigating the growth of Rayleigh-Taylor instabilities in a directly driven target5 This consisted of using large aperture, bi-level RPPs for producing a fine-scale speckle pattern, an optical wedge array to further broaden the overall far-field spot, and te1nporally smoothing the speckle pattern using smoothing by spectral dispersion. The phase plates used in these experiments were produced by large scale photolithographic and vapor deposition techniques.6
© 1992 Optical Society of America
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