Comparing 2-Shock and 3-Shock drives for Pushered Single Shell Implosions *

At the National Ignition Facility, we are exploring an alternative ignition capsule design called the pushered single shell (PSS) which utilizes a high Z pusher in between the ablator and gas fuel [1]. To mitigate ablative Rayleigh Taylor (RT) instabilities, this design uses a pusher layer that that gradually increases the high-Z concentration [2]. The high Z layer creates a dense pusher with a slower peak implosion velocity that reduces radiation losses and tamps the core, resulting in a longer burn than typical low-Z capsule implosions. However, the layer is prone to RT instabilities during deceleration which limits the advantages of the high Z pusher. The PSS campaign is investigating the balance between enhanced confinement and mix with a series of DT gas filled capsules comparing a more compressible 3-shock drive vs a more stable 2-shock laser drive. Experimental results and mix simulations are employed to determine the optimal drive that will be used for future experiments.

 

[1] D. Ho, et al APS DPP 2020

[2] E. Dewald, et al APS DPP 2020