X Band Choke Structures A. Dian Yeremian SLAC National Accelerator Laboratory

X Band Choke Structures

A. Dian YeremianSLAC National Accelerator Laboratory

4th Annual X-band Structure Collaboration Meeting,May 3rd - 5th, 2010

CERN

A.D Yeremian, 3 May 2010

Acknowledgments

Thanks very much to Sami Tantawi and Valery Dolgashev who haveinspired and help me to get involved in the world of high gradient rf structures.

The structures, I will be discussing here, are all inspired by Valery Dolgashev.



Motivation

3 Structures

- Choke Flange

-Triple Choke

-Full Choke



Motivation


High gradient RF breakdown studies include structures of various materials, some of which do not braze well or should not be brazed. There is also the desire to view the hotspots on the cell irises by a high speed camera or microscope without perturbing the electromagnetic fields by the viewport pipe. Reducing the gradient at the outer wall of the cell permits us to do these studies.



1. The choke flange was designed to replace the flange with an rf joint by an rf-lip. The joint is not always perfect and deteriorates with assembly/disassembly cycles.

2. The triple choke structure was designed in order to significantly reduce the electric and magnetic fields on the rf joint.

3. The full choke structure was designed to reduce the electric and magnetic fields at the outer radius of the cell so that we can put a view port without perturbing the fields. With the view port, a microscope or any other device could be used to view both high electric and high magnetic field areas between and during rf pulses.


X Band Choke Flange


0.1mm 2 mm4 mm

chokeR = 2.5 mm

30 m

m

11.424 GHz Choke Flange

X band Choke Flange Optimized Assuming Ideal Conducting Walls

11.00 11.20 11.40 11.60 11.80 12.00Freq [GHz]

-80.00

-70.00

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

dB(S

(Wav

ePor

t1:1

,Wav

ePor

t1:1

))

Ansoft Corporation HFSSDesign1XY Plot 2

Curve Info

dB(S(WavePort1:1,WavePort1:1))Setup1 : Sw eep1

F = 11.4236 GHzReflection (S11) = -78.2dBBandwidth = 120 MHz

120 MHz


X band Choke Flange Electric Fields

100 MW input, on-axis E=33.6MV/m, at the top of the gap E=125kV/m or 1.25kV/cm

a) Autoscaled to demonstrate max field on axis b) Manually scaled to demonstrate max field at top of choke gap


X band Choke Flange Magnetic Fields

100 MW inputOn the pipe H=57 kA/m, at top the of the gap H=225A/m

a) Auto-scaled to demonstrate max field on axis

b) Manually scaled and axis region in zoom to demonstrate max field at top of choke gap and on axis


Dipole Quadrupole Sextupole

X band Choke Flange Trapped Modes Scanning from 11 GHz Looking for 3 modes


Dipole

X band Choke Flange Trapped Modes Dipole Mode Electric Fields

Mode 1 (not trapped)

Mode 2 (not trapped) Mode 3 (not trapped)

No trapped modes! A.D Yeremian, 3 May 2010

Choke Flange Frequency Scan Overlay

-80

-70

-60

-50

-40

-30

-20

-10

11 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8 11.9 12

Frequency (GHz)

Ref

lect

ion (d

B)

perfect conductor S Steel Cesic

At f = 11.4236GHz - 78dB - 60dB - 42dB

(11.392 GHz , - 47dB)



X-band 1C-SW-A3.75-T2.6 Triple Choke Structure

f = 11.424038 GHz

4 mm

chokeR = 2.5 mm

30 m

m


11.410 11.415 11.420 11.425 11.430 11.435Freq [GHz]

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

dB(S

(Inpu

tPor

tCpl

r:1,In

putP

ortC

plr:1

))

Ansoft LLC HFSSDesign1XY Plot 1

m1

Curve Info

dB(S(InputPortCplr:1,InputPortCplr:1))Setup1 : Sw eep1

Name X Y

m1 11.4222 -26.3351

X-band 1C-SW-A3.75-T2.6 Triple Choke-Cu Structure

Frequency = 11.424038 GHzBandwidhth = 1MHzReflection (S11) = -26.3dBQo = 8660Qe = 7771Coupling = 1.11

1 MHz


0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00Distance [mm]

0.00E+000

5.00E+007

1.00E+008

1.50E+008

2.00E+008

2.50E+008

3.00E+008

3.50E+008

Com

plex

Mag

_E

Ansoft LLC HFSSDesign1XY Plot 4

m1

m2

m3

Name X Y

m1 27.7200 152518884.2512

m2 40.8100 304028128.6167

m3 54.6700 151671480.9496

Curve Info

ComplexMag_ESetup1 : LastAdaptiveFreq='11.42219GHz' Phase='0deg'

X-band 1C-SW-A3.75-T2.6 Triple Choke Structure-Cu


Electric field

Magnetic Fields Hmax = 560KA/m = 5.6KA/cmHmax@b = 510KA/m = 5.1KA/cmH@top = 40 A/m = 0.4A/cm

X-band 1C-SW-A3.75-T2.6 Triple Choke Cu, Fields Normalized to 10MW RF Losses

Emax@iris = 320 MV/mE@top = 37 KV/m


X Band Full Choke Structure 1C-SW-A3.75-T2.6 View Port-Cu

Solid model by David Martin


ChokeR = 4 mm

25 m

m

15 o

12.7mm

1C-SW-A3.75-T2.6-Full Choke View Port-Cu

f = 11.4216 GHzQo = 12416Qe = 11938

35.4

mm


-0.2 0 0.2 0.4 0.6 0.8 1 1.2

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

F = 11.42216Band width = 400KHzS11= -30.5dBQo = 12416Qe = 11938Coupling = 1.07

1C-SW-A3.75-T2.6-Choke View Port-Cu

400 KHz

Electric Field Magnetic Field

f Emax(Iris) Hmax(Iris) Emax(ch) Hmax(ch) (GHz) (MV/m) (kA/m) (KV/m) (A/m)

At location Iris Iris/cell VPbase/@VP VPbase/@VP 11.4228 350 200/580 50/28 300/200

1C-SW-A3.75-T2.6-Full Choke View Port-Cu, Fields Normalized to 10MW RF Losses



Magnetic FieldElectric Field

f Emax(Iris) Hmax(Iris) Emax(ch) Hmax(ch) (GHz) (MV/m) (kA/m) (KV/m) (A/m)

At location Iris Iris/cell VPbase/@VP VPbase/@VP 11.4228 350 200/580 50/28 300/200

1C-SW-A3.75-T2.6-Full Choke View Port-Cu, Fields Normalized to 10MW RF Losses


Summary


• SLAC has built the choke flanges to test a Cesic structure.

• KEK and Frascati are building the triple choke structures.

• SLAC are building the full choke structure with a view port.

X Band Choke Structures A. Dian Yeremian SLAC National Accelerator Laboratory

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