{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"c928578b8307602442611e1f3bf598f8d3abe00b77b00697966b4ef1442d26b4","created":"2026-10-03T07:17:56Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"8d8bd922fe086c3c45385eaed26b6a80a0bdbb9d799f3b84c14893de0d0c3d2a","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"beams.photocathode-emittance.surface-disorder","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Real cathode surfaces are bumpy and patchy at the nanometer scale, which deflects electrons as they leave. The size of this effect for real materials is not well quantified.","posed_since":"","precise":"For a photocathode with measured topography (rms height, correlation length) and work-function variation in an extraction field $E \\sim 0.1 \\text{ to } 1\\,\\mathrm{MV}/\\mathrm{cm}$, compute the contribution of slope and local transverse fields to MTE, and determine the surface quality needed for MTE below $5\\,\\mathrm{meV}$.","problem_ref":null,"references":"","settled_by":"Calculated MTE from measured surface maps compared with MTE measured on the same cathodes at several extraction fields.","status_note":"","title":"How surface roughness and work-function patchiness raise intrinsic emittance","topic_ref":"3bfc449fad2e2a963a0690d6313e4ff691a1a4e0f7733f3d2f046a8c26c65ad7"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"4f7ead691bd5eb9518f7784b8113a6f7cd032a0a96364bd5fd24cc13d8749c66","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"e8e0e26f178b718b3ac92c248a18977bddac64aaec7ea79685ac7cbad5543ed3","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"KrW3KiCy2_m-kWteV2nKXLq5Inhl8KIy7kWJvDARownVr2kacVBV0x9RNT6Dm3RZYSE3hUa92XA6lVmzrIHnBg"},"schema":"pubphys.envelope/1"},"record_hash":"4f7ead691bd5eb9518f7784b8113a6f7cd032a0a96364bd5fd24cc13d8749c66","leaf_index":685}