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HDX11 made out of Copper and Molybdenum by CERN H75vg3S18 and T53vg3MC from the NLC program

Status of x-band structure tests at SLAC. HDX11 made out of Copper and Molybdenum by CERN H75vg3S18 and T53vg3MC from the NLC program. Structure working group 16.5.2007. Status of x-band structure tests at SLAC. We are the hot topic !. ILC-News Letter.

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HDX11 made out of Copper and Molybdenum by CERN H75vg3S18 and T53vg3MC from the NLC program

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  1. Status of x-band structure tests at SLAC HDX11 made out of Copper and Molybdenum by CERNH75vg3S18 and T53vg3MC from the NLC program Structure working group 16.5.2007

  2. Status of x-band structure tests at SLAC We are the hot topic ! ILC-News Letter

  3. Scientific Motivation for the CLIC X-band proposal • Test HDS geometry and technology at high power {low phase advance, slotted iris, 4 quadrant design} • Test design optimization logic {constrains: surface field and Power*sqrt (pulse length)} • Benchmark with well known NLC copper data • Learn about material dependence (Cu vs Mo) • Learn about frequency dependence {similar tests at 30 GHz in CFT3 in 2006} • Get more statistics We are not aiming to demonstrate the CLIC structure or the CLIC gradient at X-band with these experiments !

  4. Conditioning history at 40 ns so far

  5. HDX11 Mo 50ns 75MV/m

  6. Conditioning history at 50 ns and 100 ns so far Run 100 MV/m; 50 ns ~2*10-5 Start 100 ns

  7. T53 50ns 100MV/m No breakdown in 25 hours

  8. Quick and Dirty Beta Measurement with Veetest at 100 ns down stream Calibration needed to evaluate dark current

  9. Vacuum behavior T53

  10. Vacuum behavior HDX11 Mo

  11. HDX11 conditioning statistics Or what it takes to break a structure Copper: ~ 20000 Break downs ~ 50 hours initial conditioning ~ 600 hours  Damaged Molybdenum (preliminary): ~ 11500 Break downs ~ 500 h so far  “most likely damaged too” Duration: 6 weeks with 5 weeks experiment

  12. Areas of Interest Besides the Regular Irises High Current Region Scattered Dark Spots Input Coupler Iris Patchy breakdown areas along sides of irises Areas of Discoloration

  13. HDX11 Cu post mortem inspection Input Output

  14. Comparing initial conditioning Conditioning: HDX11_Cu: 15 h, 40 ns, 80 MV/m HDX11_Mo: 50 h, 40 ns, 75-80 MV/m T53vg3MC: 10h, 50 ns, 120 MV/m ( was previously conditioned to 95 MV/m 2h, 50 ns, 80 MV/m C30vg4_W: 40h, 30 ns, 80 MV/m 90h, 30 ns, 110 MV/m C30vg4_Mo: >200h, 30 ns, 80 MV/m Refractory metals condition slower than copper Possible beneficial heat treatment is lost after weeks on air

  15. Breakdown Rates Frequency scaling experiment HDS vs HDX scaled structures show very similar performance

  16. More Breakdown Rates All HDS-type structures tested so far HDS performs consistently worse than round structuresNo significant improvement for other materials over Copper

  17. Even More Breakdown Rates All HDS-type structures tested so far HDS performs consistently worse than round structuresNo significant improvement for other materials over Copper

  18. Breakdown Rates Frequency scaling experiment of 3.5 mm round Again frequency scaling not inconsistentSlope most likely due to iris clamping

  19. Breakdown Rates Looks pretty good to me The Wuenschlist HDX; 60 MV/m; 70 ns = 9 wue T53; 110 MV/m; 50 ns = 18 wue T53; 105 MV/m; 100 ns = 20 wue H75; 97 MV/m; 150 ns = 27 wue Power for: 100, 105, 110 MV/m 97, 107, 118 MW

  20. Conclusions on recent x-band tests • Typical slow processing for Moly • Slope similar to Copper • New Hypothesis: slope is not determined by material or heating but by iris clamping ? • Heating does not help for processing or is lost after a few days • Molybdenum does not show a big advantage over Copper (Therefore focus even more on copper) • Frequency scaled structures have similar performance (BD vs grad) • HDX11 Cu revealed machining and alignment issues • Structures built out of milled bars with slots did perform worse than turned and brazed structures Structure manufacturing technology seems to play an important role The T53 could be used as a reference structure for CLIC

  21. What does it mean for CLIC ? • ~27 Wuensches have been demonstrated (Design: 18-22 needed) • T53 based structures: 9% efficiency full length at 100 ns, 40 bunches T23vg3 should work (~14% efficiency structure demonstrated) {T23, 100 bunches at 4e9, 95 MW, T33, 80 bunches, 105 MW} • See if CLICvg1 shows a better performance • Damping has to be integrated and demonstrated • ‘Old school rules’ , get engaged again with round, brazed structures made out of copper

  22. Breakdown Rates

  23. The CLIC proposal for High Power testing in NLCTA

  24. Structure parameters Scaled version of HDS11 small

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