Early-time symmetry tuning in the presence of cross-beam energy transfer in ICF experiments on the National Ignition Facility

E L Dewald; J L Milovich; P Michel; O L Landen; J L Kline; S Glenn; O Jones; D H Kalantar; A Pak; H F Robey; G A Kyrala; L Divol; L R Benedetti; J Holder; K Widmann; A Moore; M B Schneider; T Döppner; R Tommasini; D K Bradley; P Bell; B Ehrlich; C A Thomas; M Shaw; C Widmayer; D A Callahan; N B Meezan; R P J Town; A Hamza; B Dzenitis; A Nikroo; K Moreno; B Van Wonterghem; A J Mackinnon; S H Glenzer; B J MacGowan; J D Kilkenny; M J Edwards; L J Atherton; E I Moses

doi:10.1103/PhysRevLett.111.235001

Early-time symmetry tuning in the presence of cross-beam energy transfer in ICF experiments on the National Ignition Facility

Phys Rev Lett. 2013 Dec 6;111(23):235001. doi: 10.1103/PhysRevLett.111.235001. Epub 2013 Dec 2.

Authors

E L Dewald¹, J L Milovich¹, P Michel¹, O L Landen¹, J L Kline², S Glenn¹, O Jones¹, D H Kalantar¹, A Pak¹, H F Robey¹, G A Kyrala², L Divol¹, L R Benedetti¹, J Holder¹, K Widmann¹, A Moore¹, M B Schneider¹, T Döppner¹, R Tommasini¹, D K Bradley¹, P Bell¹, B Ehrlich¹, C A Thomas¹, M Shaw¹, C Widmayer¹, D A Callahan¹, N B Meezan¹, R P J Town¹, A Hamza¹, B Dzenitis¹, A Nikroo³, K Moreno³, B Van Wonterghem¹, A J Mackinnon¹, S H Glenzer¹, B J MacGowan¹, J D Kilkenny¹, M J Edwards¹, L J Atherton¹, E I Moses¹

Affiliations

¹ Lawrence Livermore National Laboratory, Post Office Box 808, Livermore, California 94550, USA.
² Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
³ General Atomics, San Diego, California 92186, USA.

PMID: 24476279
DOI: 10.1103/PhysRevLett.111.235001

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.