CLICCLICMain linac structure and Crab cavityMain linac structure and Crab cavity

Vasim KhanVasim Khan

28.08.09

In order to damp the LOM & SOM the cut-off frequency of the manifold should be below 8.0 GHz which is the lowest mode in the cavity.

b π2

p cf mn

c 22

c b

n π

a

πm

π2

cf

Circular wave-guideRectangular wave-guide

TE11 modeFc= 7.63 GHz @ b= 11.5 mm

TM11 modeFc= 7.62 GHz @ a = 30 x 26 mm x mm

To damp the HOMs the cut-off frequency of the manifold should be above 12 GHz

TE11 modeFc= 13 GHz @ b = 6.75 mm

TM11 modeFc= 13.6 GHz @ 17 x 15 mm x mm

TMmn TEmn

TM01

Fundamental mode 8.0 GHz TM11

Dipole (SOM) mode 12.0 GHz

TM11 TE11

Crab cavity profile

Blue : H-H boundary conditionRed : E-H boundary condition

90 deg.1st mode8.56 GHzTM01

180 deg.3rd mode18.66 GHz

163 deg.2nd mode15.56 GHz

First 5 modes @ 120 deg.

H-B.C.

H-B.C.

E-field H-field

120 deg.1st mode11.98 GHzTM11

180 deg.2nd mode18.65 GHzTM11

180 deg.3rd mode18.68 GHzTE11

First 5 modes @ 120 deg.

H-B.C.

E-B.C.

E-field H-field

H-H B.C. E-H B.C. H-E B.C.

10ε r 0.3tanδ 1μ r

SiC

Simulation with SiC

10ε r 0.3tanδ 1μ r

SiC

E-H B.C. H-E B.C.

Simulation with SiC

Large coupling & no SiC

H-B.C.

H-B.C.

Mode 1

Mode 2

Mode 3

Mode 1

Mode 2

Mode 3

E-field H-field

H-B.C.

E-B.C.

Mode 1

Mode 2

Mode 3

Mode 1

Mode 2

Mode 3

Large coupling & no SiCE-field H-field

E-B.C.

H-B.C.

Mode 1

Mode 2

Mode 3

Mode 1

Mode 2

Mode 3

Large coupling & no SiC

E-field H-field

dze EVL

0

ωtzz

dze EVL

0

ωtzz

Cell # 21Cell # 21

dze EVL

0

ωtzz dze EV

L

0

ωtzz

Cell # 1 Cell # 1

Monopole mode

Cell # 1

Cell # 5

Cell # 13

Cell # 24

Cell # 1

Cell # 5

Cell # 13

Cell # 24

dze EVL

0

ωtzz

dze EVL

0

ωtzz

Kick-factor calculations

Kick factor calculations ??

Monopole : dze EVL

0

ωtzz

Dipole :

3.5a dze E

3.5a dze EV

L

0

ωtz

L

0

ωtzz

Does it depend on the group velocity? i.e. Whether it is negative or positive ?

Next ??• More simulations for the Crab cavity to optimise the

dimensions, study dispersion curves.• Simulations incorporating both circular manifolds• Verification of kick-factor calculations (Bane & Gluckstern

paper)• CLIC_DDS : Simulations to verify the prediction of the fits• Background reading for corrections in chapter #1 and

necessary corrections.

Issue(s)My passport has arrived in Manchester today....I assume I got visa, need to check this evening.For extending visa, I need to know the process!