Presented by Grigory Eremeev

Grigory Eremeev

Presented by Grigory Eremeev

Outline:

- Cavities and Fields;

- Results;

- Tricks of the Trade: new shapes;

- Making of theoretical niobium.

Presented by Grigory Eremeev

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

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 mΩCu: Rs ~ 10 mΩ

↓Qnb ~ 1011 up to

Eacc = 5·107 Volts per meter

Presented by Grigory Eremeev

Ideal

9

108

10

1110

10

10

0 20 40 60

Q0

Eacc, MV/m

RealReal Real

Presented by Grigory Eremeev

High-purity Nb, sheet

inspection, CBP, etc

Improved cavity shape

Electron multiplication

Thermal breakdown

Electron field

emission

Quench

High-pressure rinsing,

cleanroom procedures

Electropolishing, low temperature

baking, …

Limitation:Limitation:

Solution:Solution:

Courtesy of Matthias Liepe

Limitation:Limitation:

Solution:Solution:

1975

3 MV/m

1995

25 MV/m

1990

15 MV/m

2005

>40 MV/m

1985

6 MV/m

2000

40 MV/m

High field Q-reduction

Further improved cavity

shapes

Presented by Grigory Eremeev

We are still limited at about Eacc = 40 MV/m for standard elliptical-shape cavities.

Best cavities

Presented by Grigory Eremeev

Tricks of the Trade:New shapes

Presented by Grigory Eremeev

Reduction of surface magnetic field by

increasing magnetic volume

Courtesy of Valery Shemelin

Re-entrant cavities

Presented by Grigory Eremeev

Re-entrant cavity breaks the barrier in 2005 at Cornell

Presented by Grigory Eremeev

For the talk by J. Sekutowicz, SLAC, January 25, 2005

Presented by Grigory Eremeev

For the talk by Takayuki Saeki, KEK

Presented by Grigory Eremeev

Hsurface = 2065 Oe

Superconductivity above Hc

Tested at Cornell on March 14, 2007…record still holds

Presented by Grigory Eremeev

Making of Theoretical Niobium:large grain and single crystal

Another Trick

Presented by Grigory Eremeev

Presented by Grigory Eremeev

Large grain cavities

P. Kneisel et al., Single Crystal Workshop

In order to improve niobium surface it was proposed to increase grain size, and to make large grain or even single crystal cavities.

Presented by Grigory Eremeev

Presented by Grigory Eremeev

Exceptional smoothness

From paper by W. Singer et al., PAC’2007

Presented by Grigory Eremeev

We are looking for other tricks…

Presented by Grigory Eremeev

Next speaker will talk more about studies related to high-field limitation of RF cavities.

More tricks?