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The Race For The Highest Gradient. Grigory Eremeev. Outline: - Cavities and Fields; - Results; - Tricks of the Trade: new shapes; - Making of theoretical niobium. - PowerPoint PPT Presentation
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Grigory Eremeev
Grigory Eremeev
Outline:
- Cavities and Fields;
- Results;
- Tricks of the Trade: new shapes;
- Making of theoretical niobium.
Grigory Eremeev
Conducting cavities can be filled with electromagnetic energy. This energy is then transferred to charged particles flying along the cavity axis.
Grigory Eremeev
Niobium best superconducting properties among all pure metals: Tc ~ 9.25 0K; Hc ~ 2000 Oe; Rbcs ~ .00001 m at 2 0K Nb : Rs ~ .00001 mCu: Rs ~ 10 mQnb ~ 1011 up to Eacc = 5107 Volts per meter
Grigory Eremeev
Ideal910810111010100204060Q0Eacc, MV/mRealRealReal
Grigory Eremeev
High-purity Nb, sheet inspection, CBP, etcImproved cavity shapeElectron multiplicationThermal breakdownElectron field emissionQuenchHigh-pressure rinsing, cleanroom proceduresElectropolishing, low temperature baking, Limitation:Solution:Courtesy of Matthias LiepeLimitation:Solution:High field Q-reductionHigh field Q-reductionFurther improved cavity shapes
Grigory Eremeev
We are still limited at about Eacc = 40 MV/m for standard elliptical-shape cavities.Best cavities
Grigory Eremeev
Tricks of the Trade:New shapes
Grigory Eremeev
Reduction of surface magnetic field by increasing magnetic volumeCourtesy of Valery ShemelinRe-entrant cavities
Grigory Eremeev
Re-entrant cavity breaks the barrier in 2005 at Cornell
Grigory Eremeev
For the talk by J. Sekutowicz, SLAC, January 25, 2005
Grigory Eremeev
For the talk by Takayuki Saeki, KEK
Grigory Eremeev
Hsurface = 2065 OeSuperconductivity above HcTested at Cornell on March 14, 2007record still holds
Grigory Eremeev
Making of Theoretical Niobium:large grain and single crystalAnother Trick
Grigory Eremeev
Grigory Eremeev
Large grain cavitiesP. Kneisel et al., Single Crystal WorkshopIn order to improve niobium surface it was proposed to increase grain size, and to make large grain or even single crystal cavities.
Grigory Eremeev
Grigory Eremeev
Exceptional smoothnessFrom paper by W. Singer et al., PAC2007
Grigory Eremeev
We are looking for other tricks
Grigory Eremeev
Next speaker will talk more about studies related to high-field limitation of RF cavities.More tricks?
Grigory Eremeev
Grigory EremeevGrigory Eremeev