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Accepted · first revision · record

Title: Why conditioning progresses with number of RF pulses, not breakdowns
Plain: New structures reach high fields only after a slow initial period of operation called conditioning. Data suggest the improvement tracks how many pulses were applied, not how many sparks occurred, and the reason is unclear.
Precise: In CLIC-type X-band structures the achievable gradient at fixed BDR improves with accumulated RF pulse count rather than accumulated breakdown count. Identify the material change during conditioning (work hardening, dislocation structure evolution, surface contaminant removal) and give a model that predicts the conditioning curve $E(N_{pulses})$ for a given material state.
Settled by: Microstructural measurements on structures stopped at successive conditioning stages, compared with the predicted evolution of the defect population.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: open
Status note: (empty)
Posed since: (empty)