{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"f96e86ae58b4eb4b46580ebe683c4f103cf96d851ac48400229ccd50df2f848b","created":"2026-10-03T07:17:56Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"93d272fee73278ec65a1b75ff3a79b08de969b195c6562397d8697dfcd70c591","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":"1","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 1e-6 to 1e-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":null,"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":"416111fd7e6fee07d8da591a9ff1426619f087a5ba70068946ba198ef0a5a6c3"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"7ab1360f4cab8f43f0f0ade18457b3d16647508716cadddd9bc1aebf936a2302","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"90df2a3519ebdf36eaf0166c87879928f4383a6c1b01aac752196a04d1584c24","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"hk9hS1V3fukJTE0_hiSZ_TLGoWnCFd457CtdTJSxhtGZX-49GdTjggjpQZwnt0FEr7pUwSZMA3g4h_7H1bsMCw"},"schema":"pubphys.envelope/1"},"record_hash":"7ab1360f4cab8f43f0f0ade18457b3d16647508716cadddd9bc1aebf936a2302","leaf_index":700}