Paper

{
  "raw_xml": "<entry>\n    <id>http://arxiv.org/abs/2602.22477v1</id>\n    <title>Fused-Silica Activation Cherenkov Detector for Pulsed D--T Fusion Yields</title>\n    <updated>2026-02-25T23:33:32Z</updated>\n    <link href='https://arxiv.org/abs/2602.22477v1' rel='alternate' type='text/html'/>\n    <link href='https://arxiv.org/pdf/2602.22477v1' rel='related' title='pdf' type='application/pdf'/>\n    <summary>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 $β^-$ 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.</summary>\n    <category scheme='http://arxiv.org/schemas/atom' term='physics.ins-det'/>\n    <published>2026-02-25T23:33:32Z</published>\n    <arxiv:primary_category term='physics.ins-det'/>\n    <author>\n      <name>N. Kaneshige</name>\n      <arxiv:affiliation>Helion Energy, Everett WA, USA</arxiv:affiliation>\n    </author>\n    <author>\n      <name>S. Alawabdeh</name>\n      <arxiv:affiliation>Helion Energy, Everett WA, USA</arxiv:affiliation>\n    </author>\n    <author>\n      <name>W. Hennig</name>\n      <arxiv:affiliation>Helion Energy, Everett WA, USA</arxiv:affiliation>\n    </author>\n    <author>\n      <name>D. Cech</name>\n      <arxiv:affiliation>Helion Energy, Everett WA, USA</arxiv:affiliation>\n    </author>\n    <author>\n      <name>M. Hua</name>\n      <arxiv:affiliation>Helion Energy, Everett WA, USA</arxiv:affiliation>\n    </author>\n    <author>\n      <name>R. Grazioso</name>\n      <arxiv:affiliation>Helion Energy, Everett WA, USA</arxiv:affiliation>\n    </author>\n  </entry>"
}