{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"af122fa3c822cea1d497f7497024e98fe771319259a830f06e3eebb9eb1c8ce8","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["c692d0ddecd29c4895dc853c3c5f536c5b79ed06d0a2f3b48256cadaaad02390","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"0a478046f0341b95ed49d52f1a6df320896f3fe03d4a640fc1acc8aa910d2d4f","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"plasma.burning-plasma.helium-ash","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"Each fusion reaction leaves a helium nucleus behind, and if helium accumulates it dilutes the fuel and stops the burn. It must be removed faster than a certain rate, and it is not certain reactors can do so.","posed_since":"","precise":"Steady burn requires the ratio $\\rho = \\tau_{\\mathrm{He}}*/\\tau_E$ of effective helium particle confinement time to energy confinement time below about 5 to 10. Predict $\\rho$ for ITER and a reactor from core helium transport, edge and divertor helium enrichment and pumping. An answer is $\\rho$ with uncertainty from validated core-edge-divertor modeling.","problem_ref":"c692d0ddecd29c4895dc853c3c5f536c5b79ed06d0a2f3b48256cadaaad02390","references":"","settled_by":"Helium transport and exhaust measurements in ITER D-T plasmas, or validated coupled modeling.","status_note":"","title":"Can helium ash be exhausted fast enough in a reactor?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"43c2ffb0dd5dd797805cfda1871fc06b3f0f1dd1790e2e5afcf1bc4c516da87b","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"389092f6e7bb501ea1c9942dbca9a555ce97b1143a51912fe3db0ef4fa3518e9","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"vOAm7BGPU6knmDDAMDhQoA0_C-R039COgzPA-M_tWpA8Xhl3uSM53NGhdw6Fk9dCjtqzhE9KWnFI1CYKWdXwDg"},"schema":"pubphys.envelope/1"},"record_hash":"43c2ffb0dd5dd797805cfda1871fc06b3f0f1dd1790e2e5afcf1bc4c516da87b","leaf_index":3548}