{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"f6cf3653d9e5a996283de544319735cd9eeb9399eebe578218d3d851a49adb5c","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["7ab1360f4cab8f43f0f0ade18457b3d16647508716cadddd9bc1aebf936a2302","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"49ddbe99b052e3a11c7f3fb951b813ce3d3384c86d4c7d88b4d851bc6f653432","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"beams.space-charge-halo.halo-loss-prediction","kind":"phenomenon","literature_status":"open","n":"2","parents":[],"plain":"Simulations cannot yet predict the tiny fraction of protons that escape the core of an intense linac beam, which is what matters for radiation damage.","posed_since":"","precise":"In MW-class proton and H- linacs (SNS, J-PARC, ESS, PIP-II) losses must stay below about $10^{-6}$ to $10^{-4}$ of the beam per unit length. Predict, blind and to within a factor 2, the halo population beyond 5 rms beam sizes from the measured initial distribution, lattice errors and space charge, and identify which mechanisms (envelope mismatch, particle-core resonances, intrabeam stripping of H- ions) dominate the measured loss pattern.","problem_ref":"7ab1360f4cab8f43f0f0ade18457b3d16647508716cadddd9bc1aebf936a2302","references":"","settled_by":"Blind prediction of halo profiles measured with high-dynamic-range diagnostics in an operating MW linac.","status_note":"","title":"Predicting halo population and fractional loss in megawatt proton linacs","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"56d6883d1183f26db5e6352986f44d5b2826b6f7bda11430c3ebfefbfe562caa","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"f4e1adfc06966ce6db6718446a8c4e17a8affa5962867aeb9899d4d07461782f","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"O5c6MoXaxMhNxd7w6DOBMvGVwz1G8yq_AKLTIMhJxD1otSJb-zbQNQ5auDo_JtYuPIwM2hga3StEXG5NB5fQCg"},"schema":"pubphys.envelope/1"},"record_hash":"56d6883d1183f26db5e6352986f44d5b2826b6f7bda11430c3ebfefbfe562caa","leaf_index":2530}