Mix, Temperature and Compression of Statistical Model Optimized Cryogenic Implosions *

We report on the x-ray continuum inferred mix, temperature and compression of direct-drive DT cryogenic layered implosions on OMEGA that were optimized with a statistical model.[1] The x-ray measurement is obtained from a new four-channel, differentially filtered pinhole imager recorded on calibrated image plate, from which an electron temperature and absolute yield are determined. The mix analysis is based on a ratio of measured x-ray and neutron yields.[2] The influence of nonequilibration of electrons and ions in the hot spot is interpreted from a database of 2‑D radiation-hydrodynamic simulations. Within limits of a few percent by atom CD (imposed by the nonequilibrium conditions), we do not find indications of hot-spot mix over the range of typically accessed implosions for highest ignition-relevant performance. The bremsstrahlung temperature and line-integrated amplitude are also spatially resolved and compared to an identical analysis of the 2-D simulation (accounting for beam geometry, laser imprint, and cryogenic layer roughness). The results suggest that our current models do not yet explain the limitations on hot-spot compression. 

 

[1] V. Gopalaswamy et al., Nature 565, 581 (2019).

[2] T. Ma et al., Phys. Rev. Lett. 111, 085004 (2013).