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Grigory Eremeev

The Race For The Highest Gradient. Grigory Eremeev. Outline: - Cavities and Fields; - Results; - Tricks of the Trade: new shapes; - Making of theoretical niobium.

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Grigory Eremeev

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  1. The Race For The Highest Gradient Grigory Eremeev Presented by Grigory Eremeev

  2. Outline: - Cavities and Fields; - Results; - Tricks of the Trade: new shapes; - Making of theoretical niobium. Presented by Grigory Eremeev

  3. Conducting cavities can be filled with electromagnetic energy. This energy is then transferred to charged particles flying along the cavity axis. Presented by Grigory Eremeev

  4. THE CAVITY Cavity cavity • Niobium – best superconducting properties among all pure metals: • Tc ~ 9.25 0K; • Hc ~ 2000 Oe; • Rbcs ~ .00001 mΩ at 2 0K Nb : Rs ~ .00001 mΩ Cu: Rs ~ 10 mΩ ↓ Qnb ~ 1011 up to Eacc = 5·107 Volts per meter Presented by Grigory Eremeev

  5. 11 Ideal 10 10 Q0 10 Real Real Real 9 10 8 10 0 20 40 60 Eacc, MV/m Presented by Grigory Eremeev

  6. 1975 3 MV/m 1985 6 MV/m 1990 15 MV/m 1995 25 MV/m 2005 >40 MV/m 2000 40 MV/m Limitation: Thermal breakdown High field Q-reduction High-purity Nb, sheet inspection, CBP, etc Electropolishing, low temperature baking, … Solution: Electron field emission Electron multiplication Quench Limitation: High-pressure rinsing, cleanroom procedures Further improved cavity shapes Improved cavity shape Solution: Courtesy of Matthias Liepe Presented by Grigory Eremeev High field Q-reduction

  7. Best cavities We are still limited at about Eacc = 40 MV/m for standard elliptical-shape cavities. Presented by Grigory Eremeev

  8. Tricks of the Trade: New shapes Presented by Grigory Eremeev

  9. Re-entrant cavities Reduction of surface magnetic field by increasing magnetic volume Courtesy of Valery Shemelin Presented by Grigory Eremeev

  10. Re-entrant cavity breaks the barrier in 2005 at Cornell Presented by Grigory Eremeev

  11. For the talk by J. Sekutowicz, SLAC, January 25, 2005 Presented by Grigory Eremeev

  12. For the talk by Takayuki Saeki, KEK Presented by Grigory Eremeev

  13. Superconductivity above Hc Tested at Cornell on March 14, 2007…record still holds Hsurface = 2065 Oe Presented by Grigory Eremeev

  14. Another Trick Making of Theoretical Niobium: large grain and single crystal Presented by Grigory Eremeev

  15. Presented by Grigory Eremeev

  16. Large grain cavities In order to improve niobium surface it was proposed to increase grain size, and to make large grain or even single crystal cavities. P. Kneisel et al., Single Crystal Workshop Presented by Grigory Eremeev

  17. Presented by Grigory Eremeev

  18. Exceptional smoothness From paper by W. Singer et al., PAC’2007 Presented by Grigory Eremeev

  19. We are looking for other tricks… Presented by Grigory Eremeev

  20. More tricks? Next speaker will talk more about studies related to high-field limitation of RF cavities. Presented by Grigory Eremeev

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