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