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X-band Single Cell and T18_SLAC_2 Test Results at NLCTA

X-band Single Cell and T18_SLAC_2 Test Results at NLCTA. Faya Wang Chris Adolphsen Jul-9-2009. Single cell SW structure test result Breakdown with constant gradient but different pulse heating Breakdown with constant pulse heating but gradient 2 nd SLAC made T18 test result.

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X-band Single Cell and T18_SLAC_2 Test Results at NLCTA

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  1. X-band Single Cell and T18_SLAC_2 Test Results at NLCTA Faya Wang Chris Adolphsen Jul-9-2009

  2. Single cell SW structure test result Breakdown with constant gradient but different pulse heating Breakdown with constant pulse heating but gradient • 2nd SLAC made T18 test result

  3. from Valery Dolgashev and James Lewandowski

  4. Two 3 dB hybrid RF In Small load Big load To big load 45 dB coupler Ion pump Structure Ran cooling water through a quadrupole magnet adjust structure temperature. Half cooling jacket X-band Current Monitor

  5. Input RF Pulse Maximized initial pulse to reduce fill time

  6. RF Processing History During First 100 Hours Detect breakdown from the large (> 0.8 on above scale) current produced

  7. Pulse Heating RF Power and Heating Measurements and Simulations Simulations based only on measured input power

  8. Breakdown Study with Constant Gradient but Different Pulse Heating from the Pre-Fill ‘Warm-up’ Peak Pulse Heating Input Power Reflected Power

  9. Breakdown Rate for Fixed Gradient

  10. Comparison of these results with those from a similar structure (same a/l) tested at the Klystron Test Lab where the pulse shape was fixed so the gradient varies with pulse heating

  11. Breakdown Study with Constant Pulse Heating

  12. Breakdown Rate for Fixed Peak Pulse Heating (139/129)^25 =6.5 (139/119)^25 = 48.6 Flat top gradient for 160 ns.

  13. Cumulated Phase Change Test Results from Second SLAC T18 Disk Structure Field Amplitude 120°

  14. This time, processed structure by progressively lengthening the pulse at constant gradient (110 MV/m)

  15. Comparison of current BDR rate (blue circle) with the rate curves from the First SLAC T18 structure at different processing times T18_SLAC_2

  16. RF Breakdown Locations Blue dot: T18_SLAC_2 after 250 hrs running Red square: T18_SLAC_1 after 1200 hrs running T18_SLAC_2

  17. Summary • Reduce fill time with SLED for SW cavity test • It is possible to separate pulse heating and gradient with SLED for the same structure. • T18 is a good structure, however it is not clear why there is a hot cell.

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