{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"5b8a81b603dbd96a92e101fb420075d3997fb5802825852edc9c617ad51ea5de","created":"2026-10-03T07:18:08Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"2992d1ff3fa41d8646410e4eff3705eb11445cb70e006b4b51c87059140c1fba","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":"1","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":null,"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":"b2068d5f1bac3966c9cee581f56630c3c4fcfd678ae16ee7f5ea4ea28a182b60"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"c692d0ddecd29c4895dc853c3c5f536c5b79ed06d0a2f3b48256cadaaad02390","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"28afd68d8f1646a5aeccab6043021b889eb0902bfb421e9215f8da3320f4905d","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"JChkJrm2eyFDm-uzyA08q46PLxGjbt7d4NbMCUPsNXue19kP5wPxBcx_wQfyUrIYwNRaHE-NoiVsTwGzRCUYBg"},"schema":"pubphys.envelope/1"},"record_hash":"c692d0ddecd29c4895dc853c3c5f536c5b79ed06d0a2f3b48256cadaaad02390","leaf_index":1820}