A simple, generalised methodology is developed for the estimation of the Lawson number (a.k.a. the ‘fusion triple product’) and related quantities of interest, using information contained in the diagnostic probe files produced by First Light Fusion’s (FLF) Hytrac and B2 design codes. The calculation of the confinement time considers cases where the neutron output of the target comes in a number of distinct ‘emission events’, each of which may be multi-modal in nature and separated from one another in time over the target operation. For targets whose yield comes from a single pulse of neutrons, our modified definition reduces to the commonly used definition for conventional laser-driven hot spot ignition designs. The number density and temperature of the fuel ions are based on a weighted average of suitable characteristic values from all neutron emission events that depend on the reaction rate in the fusion fuel. The fuel ion density is also generalised to account for arbitrary mixtures of reactive and inert ion species. Three examples are given, showing detailed traces and the operation of the method. The tool has then been run on a large number of FLF designs, including future pipeline designs and the design which has recently demonstrated fusion [1, 2]. The results are plotted following Wurzel and Hsu [3] and reveal the unique nature of FLF’s approach, which has very high values of the product of fuel ion number density and confinement time.


D. A. Chapman, M. R. Betney and N. A. Hawker