WG-5@KEKHiroshi Matsumoto, Sergey KazakovSchedule for ILC 45 MV/m Input Coupler(disk type and capacitive coupling, Kazakov

type)

2) fix the electric parameters

1) contract for ILC 45 MV/m

5) order the ceramics

(disk type)

3) make mechanical design

6) R&D

4 5 6 7 98 1110 112 2 32005 2005

4) critical discussion with company for technical issues in details

• brazing test

• DLC test

• isolator

• waveguide

using S-band TRW at KEKB

HA-997

mainly design work mainly design

work

to cavity

rf power7 months

3 months

WG-5@KEKHiroshi Matsumoto, Sergey Kazakov

Possible Structures for Input Coupler

Input coupler comprises of four modules:

1) antenna at cold side

2) rf window

3) coaxial line

4) coaxial transformer

antenna

rf window

coaxial line

coaxial transformer

rf power

rf power

possible structures

cylinder shape rf window

disk shape rf window

rf power

WG-5@KEKHiroshi Matsumoto, Sergey Kazakov

High Purity Alumina & Diamond-like Carbon Carting

Major characteristics of HA-997 (NTK)- Alumina contents (%): 99.7- Specific gravity: 3.95- Dielectric constant (): 9.8~9.9 (8-GHz)-Temperature coefficient of (ppm/ºC): +90~+110- Dielectric loss tangent (Tan ): 3x10-5 (8-GHz)

Advantages • almost uniform grain size.• no large voids found between grain boundaries.

Super hard diamond-like carbon coating using Gas Cluster Ion Beam Assisted Deposition (GCIB). Nomura Plating Co.,Ltd.

GCIB CVD

Hardness [GPa]: >50 20~30

Young’s modulus: 270 140

Component: Carbon Carbon+H2

Diamond content: Rich Weak

Density: High Low

Heat resistant: 500ºC <400ºC(at air)

Flatness (Ra, nm): <0.5 0.5 Diamond-like carbon with 100-nm of coating thickness will provide good uniformity.

NOTE: need investigate rf characteristics at high power.

Al2O3

99.7%

WG-5@KEKHiroshi Matsumoto, Sergey Kazakov

High Power Test Using TWR

We used Traveling Wave Resonator (TWR) to conduct high power tests of rf window ceramic disks, which were made with varying fractions of sintering binder (MgO).

Cutaway view of rf window at S-band frequency.

ceramic diskt: 3.5-mm, Ø92-mm

ceramic diskceramic disk

waveguide

WG-5@KEKHiroshi Matsumoto, Sergey Kazakov

Basic Technologies:-low electric field gradient at air side < 1 kV/mm- high purity ceramic >99.7%- use new brazing material Ag:Cu Au:Cu (:Ti, option)- surface coating TiN, and or diamond-like carbon

Input Coupler for ILC 45 MV/m

USE NEW RF FEED SYSTEM.

- separate coupling adjustment from coupler adopted the jB generator. (system simple) - no tapering part at rf window to reduce multipactoring. (improve reliability) - try to omit an rf window for room temperature side. (reduce cost)

Klystron

CavityW.G.

Coupler

g/4 impedance matching

Disk type window

not scaledAnchors using

Invar 9-cell x 4 (45 MV/m)

3dB HYBRIDRF load

Klystron

jB generator

Z(L)=jZ0tan(2Lg)

Air? or Vacuum?

Isolator

Vacuum or dray N2

H. Matsumoto, S. Kazakov

5-MW, 1-msec 0.9 kV/mm @ 5-MW (~1 kV/mm @ Air)EIA650 (8.255-cm x 16.51-cm)

* Electric field gradient in the waveguide (kV/mm) @ 5-MW

L-band (8.255-cm x 16.51-cm): 0.9 -> seems not enough margin in air

S-band (3.404-cm x 7.21-cm) : 2.2 -> no good in air,

good in SF6 (but no good at 10-MW)

WG-5@KEKHiroshi Matsumoto, Sergey Kazakov

Gas Pressure VS Breakdown Voltage

Air 1

N2 1

SF6 2.5

SF6(30%)+Air(70%) 2

C5F8 (Freon) 5.5

H2 0.5

Relative electric strength of various gases at atmospheric pressure.

From Paschen curve in figure, high gas pressure dose not great contribute to increase the breakdown voltage. The breakdown voltage in a vacuum is much higher than the other gases. So, we would like to consider the vacuum type waveguide system for a backup scheme.

Comparison of the vacuum and air for system configuration Items Vacuum Air

Dielectric strength (kV/mm) : 7~19 (practical) ~1.0 (practical) (at S-band) 2.9 (ideal)Equipment: Ion pump, Gages Blower, Filters (dust, mist) Maintainability: Very simple No good (need change the filters frequently) Environment-friendability: Very good Good (but large amount of wasted parts, noisy blower sound) System reliability; Very good Good (but, consider: blower lifetime, vacuum leak at coupler, rf phase stability)