Taking beryllium ablator implosions to larger scale on the NIF*

A series of 4 cryo-layered implosion experiments with 900 µm outer radius Be ablators has been performed at the NIF.  The first three used similar Cu-doped Be capsules, and the fourth used a thicker layer of Cu dopant to move off the “rocket curve” of the first three and maintain velocity while preserving remaining mass; this fourth implosion produced the highest yield of the set.  A model of the hydrodynamic instability-driven mixing between ablator and fuel was developed that reduced the compressibility of the fuel and reproduced the stagnation observables the first three implosions.  This model was then used to successfully predict the performance of the fourth.  This model can now be used to explore the performance of Cu-doped Be capsule implosions at larger (+20% and +30%) scale on the NIF.  The phenomena that establish the seeds and growth of instabilities that mix ablator and fuel do not necessarily scale with the capsule size and velocity.  As a result, the model predicts the performance at larger scales should be factors of several better than what one obtains from the simply scaling capsule radius and fuel velocity.