Summary: UKAEA have conducted a review of First Light Fusion Ltd’s recent (485 series) experimental campaign. The UKAEA technical team involved have had the opportunity to interact with the FLF experimental team as part of the review. The review included assessments of the experimental planning, scientific equipment used and associated diagnostics, processes to extract and analyse the data obtained from the diagnostics and analysis included within the associated experimental report.

The experimental campaign comprised 21 high velocity impact experiments (‘shots’) overall. 12 of these were reported to have used deuterium-fuelled (base-case) targets, one was a deuterium design variant shot, four were hydrogen null shots and a further four were test shots. UKAEA staff witnessed a sub-set of these which were two deuterium-fuelled target shots; the first took place on the 22nd February 2022 and yielded no detection events (reportedly due to projectile failure); the second (successful) shot on the 4th March 2022 yielded three scintillator events and a single 3He detection event within the defined time windows.

In assessing the experimental campaign as a whole, the diagnostic data obtained and analyses performed from the experiments in aggregate, and with detailed consideration of terrestrial background or other potential sources of spurious signals, we support FLF’s finding that high energy particles have been detected. In the context of fusion experiments the number of events detected is small. However, the events detected and the associated temporal analysis are sufficient to indicate a link to the impact experiments using deuterium-loaded targets. The aggregated time-of-flight data comprising 29 detection events obtained using the scintillator array (each event corresponds to the detection of a single particle), together with the basic analysis performed to estimate a neutron energy range provides some evidence that neutrons have been produced which would be consistent with the energy of those produced in D–D fusion processes. The supporting 3He detection events within an expected time window following the expected fusion time are fewer, though in aggregate do provide some complementary evidence through a separate detection system to the scintillator array that neutrons are present.