Early-time symmetry tuning in the presence of cross-beam energy transfer in ICF experiments on the National Ignition Facility.
Phys Rev Lett
; 111(23): 235001, 2013 Dec 06.
Article
en En
| MEDLINE
| ID: mdl-24476279
ABSTRACT
On the National Ignition Facility, the hohlraum-driven implosion symmetry is tuned using cross-beam energy transfer (CBET) during peak power, which is controlled by applying a wavelength separation between cones of laser beams. In this Letter, we present early-time measurements of the instantaneous soft x-ray drive at the capsule using reemission spheres, which show that this wavelength separation also leads to significant CBET during the first shock, even though the laser intensities are 30× smaller than during the peak. We demonstrate that the resulting early drive P2/P0 asymmetry can be minimized and tuned to <1% accuracy (well within the ±7.5% requirement for ignition) by varying the relative input powers between different cones of beams. These experiments also provide time-resolved measurements of CBET during the first 2 ns of the laser drive, which are in good agreement with radiation-hydrodynamics calculations including a linear CBET model.
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MEDLINE
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En
Revista:
Phys Rev Lett
Año:
2013
Tipo del documento:
Article
País de afiliación:
Estados Unidos