Crab Cavity Study with GDFIDL

Narong Chanlek and Roger Jones

20/12/06

Crab Cavity

• Crab cavities are used for the ILC in order to increase the luminosity of the colliding beams at the interaction point.

• These cavities use dipole electric field to kick the bunches into a suitable angle.

20/12/06

R.M. Jones et al.,linac 2006

Crab Cavity

• TM110 dipole mode is used to operate.

• Cavity shape and field structure

(G. Burt and P. Goudket)

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Simulation

• Shape of one cell model by GDFIDL

• GDFIDL (finite difference algorithms) is used to simulate.• Higher order modes (HOMs), lower order modes (LOMs) and

same order modes (SOMs) are characterized.• Why do we need to simulate:

- HOMs, LOMs and SOMs can also be excited in the cavity.

- These mode can disrupt the bunches.

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Cavity Shape

• Geometric parameters of the cavity

shapes

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• 5 cell Niobium prototype cavity

• Schematic view of the cavity shape

Results

• Arrow plots of E-field

Monopole

@ 2.75 GHz

Quadupole

@ 5.45 GHz

dipole

@ 4.10 GHz

Sextupole

@ 6.74 GHz

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Results

• Dispersion diagram for single-cell Crab cavity

Mode used for bunch DEFLECTION 3.9 GHz

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Light line plot

Summary

20/12/06

• Crab cavity uses TM110 dipole mode to rotate the

beam in order to achieve an effective collision.

• The frequency modes of Crab cavity are studied

by GDFIDL.