{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"ea652a161ec9f371f7ad6bd4dff8f9f265532760d8909a825ce126573081fbd9","created":"2026-10-03T07:17:56Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"cc4320e2d76ccaf37851b440ffaf022bb077b4f20b8612a102d0ce5b55692e94","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"beams.collective-instabilities.lhc-heat-load-spread","kind":"phenomenon","literature_status":"partially-resolved","n":"1","parents":[],"plain":"Stray electrons multiplied by the beam heat the cold beam pipes of the LHC, and some sections heat about twice as much as nominally identical ones.","posed_since":"2015","precise":"With 25 ns bunch spacing the beam-induced heat load on LHC arc beam screens differs between nominally identical sectors by a factor of approximately 2-3, attributed to differences in secondary electron yield (SEY). Determine the surface process that prevents some screens from conditioning (SEY reduction under electron bombardment) and predict, from surface history, which sectors condition.","problem_ref":null,"references":"","settled_by":"Laboratory conditioning of beam-screen samples with the two surface histories reproducing the measured SEY difference, consistent with in-machine heat loads.","status_note":"Surface analysis of beam screens extracted from the LHC (published around 2021) tied high heat load to a different copper-oxide composition and less surface carbon; why the sectors differ is not settled.","title":"Why identical LHC arcs show very different electron-cloud heat loads","topic_ref":"dd60e631adb08b9b18495c7a3ab1cfd2ffd7375b33108ba5cf5ec6cce7af2868"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"28b33a3ac82768f6777755d11bb50dca30b3ab2f4384b16baa79004c44cb3082","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"a01166f1750079cd8f461b0b7517a847bf52abfbf07c8e1d261a99164bffd574","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"1SnzK2gb8mB7gvdSvHtKLv9G0Fz-SPg_E9V5ME51T_X8Qfi7KwB0yowpWMZplzgzOiPag3X-Xmuf-nV_FdEnBw"},"schema":"pubphys.envelope/1"},"record_hash":"28b33a3ac82768f6777755d11bb50dca30b3ab2f4384b16baa79004c44cb3082","leaf_index":658}