Shock timing on the National Ignition Facility: First experiments

P M Celliers ,S Le Pape,T Döppner,L.V Berzins,A Nikroo,C Choate,K Widmann,B Haid,C Castro,T Parham,G Frieders,K Jancaitis,D Trummer,E Giraldez,C Widmayer,S.J Brereton,P Dinicola,J Fair,Harry B Radousky ,D H Kalantar ,S M Pollaine ,T R Boehly ,Michael Shaw ,H F Robey ,E L Dewald ,B M Van Wonterghem ,O L Landen ,S N Dixit ,D R Farley ,Christopher A Haynam ,C A Thomas ,P A Sterne ,D M Holunga ,G Ross ,B J Macgowan ,E G Dzenitis ,M J Edwards ,R P J Town ,J D Moody ,J L Milovich ,M B Schneider ,Hema Chandrasekaran ,D G Hicks ,K N Lafortune ,G W Collins ,J J Kroll ,K Krauter ,A V Hamza ,A.l Throop ,N B Meezan ,B K Young ,T N Malsbury ,Keith R Coffee ,C R Gibson ,Daniel Clark ,E R Mapoles ,J Horner ,K A Moreno ,J D Lindl ,M W Bowers ,D D Meyerhofer ,J H Eggert ,L J Atherton ,O S Jones ,E T Alger ,Raymond F Smith ,S W Haan ,R E Olson ,D A Callahan ,J L Kline ,J D Sater ,S D Bhandarkar ,S.g Azevedo ,C F Walters ,D H Munro ,P Datte ,E I Moses

doi:10.1051/epjconf/20135902004

Abstract

An experimental campaign to tune the initial shock compression sequence of capsule implosions on the National Ignition Facility (NIF) was initiated in late 2010. The experiments use a NIF ignition-scale hohlraum and capsule that employs a re-entrant cone to provide optical access to the shocks as they propagate in the liquid deuterium-filled capsule interior. The strength and timing of the shock sequence is diagnosed with velocity interferometry that provides target performance data used to set the pulse shape for ignition capsule implosions that follow. From the start, these measurements yielded significant new information on target performance, leading to improvements in the target design. We describe the results and interpretation of the initial tuning experiments.

Highlights

INTRODUCTIONIn the ideal case each element of the fuel layer must be compressed by each shock in succession, a condition that will maintain low entropy in the fuel layer
The strength and timing of the shock sequence is diagnosed with velocity interferometry that provides target performance data used to set the pulse shape for ignition capsule implosions that follow
The first two shots revealed a significant discrepancy between the observed shock velocity history and pre-shot predictions based on simulations

Summary

INTRODUCTION

In the ideal case each element of the fuel layer must be compressed by each shock in succession, a condition that will maintain low entropy in the fuel layer This situation is achieved by controlling the strength and launch times of these shocks such that all four shocks merge nearly simultaneously at a common point near the fuel ice-gas interface, Fig. 1(b). This situation of near simultaneous mergers is achieved by making adjustments to the power history of the drive pulse, which in turn adjusts the strength and timing of the shocks. We describe the initial results obtained on NIF using this technique

TARGET DESIGN AND VELOCITY MEASUREMENT

INITIAL RESULTS

CONCLUSION