arXiv:2602.22477v1 Announce Type: new
Abstract: We demonstrate a compact, non-toxic, low-cost neutron-yield diagnostic for pulsed D–T fusion systems using an undoped fused-silica (SiO$2$) rod as both activation target and Cherenkov radiator. D–T neutrons (14.1 MeV) activate $^{28}$Si and $^{16}$O to produce short-lived $^{28}$Al ($T{1/2}=134,mathrm{s}$) and $^{16}$N ($T_{1/2}=7.13,mathrm{s}$). The resulting $beta^-$ particles exceed the Cherenkov threshold and generate UV–visible light detected by a fast photomultiplier tube. A SiO$_2$ rod of dimensions $6,mathrm{in}times1,mathrm{in}$ (length $times$ diameter) is optically coupled and read out with a CAEN DT5730 digitizer operating in list mode with digital pulse processing. The post-pulse count rate is fit using fixed $^{16}$N and $^{28}$Al half-lives together with background terms to infer neutron fluence. Testing at the ZEUS D–T Dense Plasma Focus established a reference calibration and agreement with a praseodymium-calibrated silver activation detector. Measurements near a D–D Dense Plasma Focus show no activation signal, confirming D–T selectivity. The diagnostic enables pulse-to-pulse yield measurements within minutes following a pulse and is being deployed on Helion Energy’s seventh fusion prototype, Polaris.