Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Linear-time Algorithms for the 2-connected Steiner Subgraph Problem On Special Classes of Graphs

The 2-connected Steiner subgraph problem is that of finding a minimum-weight 2-connected subgraph that spans a subset of distinguished vertices. This paper presents linear-time algorithms for solving the 2-connected Steiner subgraph problem on two special classes of graphs, W4-free graphs and Halin graphs. Although different in detail, the algorithms adopt a common strategy exploiting known decompositions. As a special case, the algorithms also solve the Traveling Salesman Problem on W4-free graphs and Halin graphs