Understanding the enhanced hohlraum drive that follows high yield

The 1.35 MJ yield shot N210808 at the National Ignition Facility began a new era in enhanced hohlraum heating. The capsule imploded after the drive laser was off, and thus during a period of time in which the signal from the Dante instrument (that measures hohlraum drive via x-ray output through the laser entrance hole) was dropping in time. After the capsule produced its high yield, the Dante signal rose, implying a non-laser source of hohlraum heating. This observation is the first of its kind. We discuss here the many possible "suspects" that may have caused this enhanced hohlraum heating. We identify the most likely cause. This understanding may allow future shots to be optimized to increase this heating enhancement. We also point out that in future, even higher yield shots, another phenomenon may also contribute to enhanced hohlraum heating.