More energy was produced than was supplied by ultraviolet (UV) lasers (creating x-rays in the gold chamber wall to compress the spherical hollow capsule creating a dense, high-temperature, high-pressure plasma) during each of the National Ignition Facility (NIF) ignition achievements of 5 Dec 2022 and 30 July 2023 for inertial confinement fusion (ICF).
Assuming the fusion reaction $_1^2\mathrm{H} + _1^3\mathrm{H} \rightarrow _2^4\mathrm{He} + _0^1\mathrm{n} + 17.5\, \mathrm{MeV}$, measurements of the excess energy generated were determined by measuring the number of neutrons (using multiple neutron diagnostics) and multiplying that number by 17.59 MeV. Great significance was rightfully placed on the neutron data. I am wondering if there is proof, via showing and analyzing the full neutron (including low energy neutrons) and photon energy spectra (including x-rays and gamma rays), that this is the only reaction that was meaningfully contributing to the production of the excess energies. Using conservation of energy and momentum and assuming small input energy we would expect to have approximately, 3.54 MeV for the helium kinetic energy and 14.05 MeV for the free neutron. Presumably the only neutrons counted were the ones near 14.05 MeV. Actual input energies would cause deviations from the 14.05 MeV neutron energies. It is understood that the x-ray spectrum might be contaminated by x-rays produced by the incidence of the UV light on the gold chamber wall. The analyses would need to include prior background data and attenuation of the spectra, say in going through the initially dense plasma and the gold chamber wall. Maybe someone at NIF has done such analyses or could do the analyses and provide basic conclusions based upon existing/future data.
With 3.54 MeV available from each $\alpha$ and 14.05 MeV available in each neutron in the exothermic $\mathrm{D} + \mathrm{T}$ fusion reaction, other processes or secondary reactions might be, for example, the endothermic reactions $\mathrm{n} + \mathrm{T} + 6.26\, \mathrm{MeV} \rightarrow\mathrm{n} + \mathrm{n} + \mathrm{D}$ and $\mathrm{n} + \mathrm{D} + 2.22\,\mathrm{MeV} \rightarrow \mathrm{n} + \mathrm{n} + \mathrm{p}$. Those potential reactions could produce extra neutrons and thus alter the total energy production computations, even if only neutrons near 14.05 MeV are counted. There are other potential processes/reactions, according to my research, with both $\mathrm{D}$ and $\mathrm{T}$ having nuclear magnetic moments (of 0.857 and 2.979 nuclear magnetons). If the $\mathrm{D} + \mathrm{T}$ fusion reaction is not pure, that might call into question the validity of the $\mathrm{D} + \mathrm{T}$ energy production results. If not pure, it would be best, if possible, to determine estimates of the numbers of the other reactions according to the data, to do a proper accounting of energy production.
It is supposed that the energies of the neutrons were at least found using time of flight (TOF) methods. It is also supposed that n-$\gamma$ discrimination techniques were used to remove the counting of background or spurious x-rays or $\gamma$-rays as being falsely counted as neutron TOF detections with approximately 14.05 MeV energies.
Verifying the energy increase of 3.54 MeV for each $\alpha$ in the plasma for each$\mathrm{D} + \mathrm{T}$ fusion reaction would be useful but it might be difficult because of the large amount of incident UV or x-ray energy initially provided prior to the plasma and difficulties in measuring the precise energy produced in the exploding plasma. Though helpful, I don't consider energy verification as proof of reaction purity for $\mathrm{D} + \mathrm{T}$ fusion.
We should not automatically assume that $\mathrm{D} + \mathrm{T} \rightarrow \alpha + \mathrm{n}$ nuclear fusion is the only reaction, without testing out the hypothesis. We need to do the most reasonably complete experimental measurements (principally using the full spectra) and the most reasonably full analyses. If the overall question cannot be currently answered due to lack of equipment/measurements, maybe someone can more fully answer the question in the future for other ignition events, after proper measurements and analyses are done.
