Testing laser-plasma interactions relevant to an upgraded laser at the National Ignition Facility*

A laser upgrade is being proposed with the goal of delivering an enhanced yield capability (EYC) at the National Ignition Facility (NIF), pushing neutron yields significantly beyond the regime currently accessible. An experimental campaign was designed to study laser-plasma interaction (LPI) in a 2.6+ MJ laser parameter space to help inform the design direction and facility needs/choices. To utilize the increase in energy and perhaps power delivered by an upgraded NIF laser, a larger hohlraum and capsule size are needed relative to current igniting designs, driven by a longer laser pulse. All these changes can eventually lead to higher LPI that can compromise performance. The design chosen to explore LPI relevant to an upgraded NIF laser is a 1.09x hydroscale of the current Hybrid-E platform. Cross beam energy transfer (CBET) is a key tool for tuning implosion symmetry. In this campaign, we have increased the wave length detuning (Dl) between the outer and inner cones in stages to study how LPI scales with increasing inner cone power.

In this talk we will present the results of the first four experiments conducted during FY24. We will show how backscatter LPI scales with Dl, images of the beam propagation to the hohlraum walls, gold bubble growth, shock velocities, and implosion symmetry.