1. Pre-breakdown and Breakdown Phenomena on Contacts in Vacuum Interrupters From Edgar Dullni’s Presentation ABB Group

2. Specs They WANT breakdowns (while we try to avoid them like the plague) Specs: – Voltages from 6 kV to 40 kV – Interruption of short circuits with currents up to 63 kA – Gap distance 10-20 mm E. Dullni ABB Group RF Meeting 3rd August 2011 Rocío Santiago Kern E. Dullni, MeVArc 2011

3. OFC electrodes with possibility of in-situ sputter cleaning : Δ Without O With Pre-cleaning of contacts has no effect on first low voltage withstand of contacts Final level depends on pre- cleaning processes Rate of voltage improvement depends on surface roughness S. Kobayashi ISDEIV 2010 Results: Part 1/1 E. Dullni ABB Group RF Meeting 3rd August 2011 Rocío Santiago Kern

4. OFC electrodes with possibility of in-situ sputter cleaning: Δ Without O With Pre-cleaning of contacts has no effect on first low voltage withstand of contacts Final level depends on pre- cleaning processes Rate of voltage improvement depends on surface roughness S. Kobayashi ISDEIV 2010 In DC-experiments we observe the opposite!! If we clean the surface by sputtering, do we have same results? Results: Part 1/1 E. Dullni ABB Group RF Meeting 3rd August 2011 Rocío Santiago Kern

5. Breakdown Field E1E1 E sat N C N’ C (number of breakdowns necessary to achieve conditioning) Vacuum Air Vacuum Exposure to air reduces the breakdown field Re-conditioning can be achieved by a reduced number of breakdowns N’c < Nc Adapted from S. Kobayashi ISDEIV 2010 Results: Part 1/2 E. Dullni ABB Group RF Meeting 3rd August 2011 Rocío Santiago Kern

6. Breakdown Field E1E1 E sat N C N’ C (number of breakdowns necessary to achieve conditioning) Vacuum Air Vacuum Exposure to air reduces the breakdown field Re-conditioning can be achieved by a reduced number of breakdowns N’c < Nc Adapted from S. Kobayashi ISDEIV 2010 Is it applicable to RF structures after being tested? Results: Part 1/2 E. Dullni ABB Group RF Meeting 3rd August 2011 Rocío Santiago Kern

7. Results: Part 2 Pulsed HV vacuum breakdown - 260 ns flat top voltage pulses up to 500kV SS Electrodes (originally cleaned) with Ø 80 mm Main outcome: Over 6mm gap it doesn’t matter what is in the anode or cathode E. Dullni ABB Group RF Meeting 3rd August 2011 Rocío Santiago Kern E. Dullni, MeVArc 2011