Understanding hohlraum drive in low-fill hohlraums on NIF*

Over the past few years, we have been focusing our attention on low-fill, larger case-to-capsule ratio hohlraums in NIF experiments.   These low-fill hohlraums have, in general, been proven to have low laser-plasma instability (LPI) losses, which simplifies our analysis and understanding.  For DT implosions that are nearly 1-d, neutron yield should scale as ~ v ^7.7 S^4.5, where v is the implosion velocity and S is the dimension of the capsule.  Last year, we put our attention on understanding the factors that control symmetry in these hohlraums in order to achieve a nearly 1-d implosion.   Ultimately, we will need to understand the trade-off between the capsule size, hohlraum size, and the achievable implosion velocity, given the laser energy/power available on NIF.  In order to better understand the trade-off between size and achievable velocity, we are comparing hohlraum drive across the suite of designs.  These designs use different wall materials, case-to-capsule ratios, initial LEH sizes, beam pointing, ablator materials, laser energies and powers.  This talk will describe the scaling of hohlraum drive with these parameters and how this scaling can be used to better optimize our designs.