1. 1.3GHz Input Coupler for ILC
IHEP RF

2. Outline Design Fabrication
The major results of simulation calculation (review)
The mechanical design
Fabrication
Have been done
To be done

3. Background
By investigating and considering our fabrication experiences, we choose the STF baseline type coupler as ILC 1.3GHz coupler design prototype. That is to say, the coupler have two plate windows with choke structure, one is in low temperature and another is in normal temperature .
In phase I, we aim to design and fabricate a fixed coupling coupler; and in phase II, a variable coupling coupler will be designed.

4. Coupler Specification
Frequency
1.3 GHz
Power
Test: 1MW, 1.5ms,5Hz (average:7.5kW)
Oper: 300kW,1.5ms,5Hz (average:2.25kW)
Two windows
Safe operation
Clean cavity assembly for high gradients
2 K heat load
0.06 W
5 K heat load
1 W
80 K heat load
8 W
Diagnostic
Sufficient for safe operation and monitoring Qe
Fixed：2×106

5. RF Structure of Coupler
Two coaxial type windows;
Cold coaxial: 50 Ohms, 60mm diameter;
Warm coaxial: 50 Ohms, 81mm diameter;
Flexibility: 4 bellows in the warm coaxial;
Doorknob: WR650 waveguide - 104mm coaxial transition;
Ceramics: Al2O3 with TiN coating on vacuum side;
Copper plating on stainless steel coaxial.
Cold part
Warm part
Doorknob

6. Power Transmission Performance
The |S21| frequency sweep curve describes the power transmission performance: Mag(S21)= shows a good RF structure design from the view of power transmission Passband: 200MHz when VSWR<1.1; 250MHz when VSWR<1.2 6

7. Qe Calculation Two parameters related with Qe were studied:
the coupler input port position (the dimension D);
the antenna penetration depth (the dimension H);
Result of calculation:
To obtain Qe= 2×106，We choose the distance from end cell to coupler port center D=60mm, adjust the antenna penetration near 8mm;

8. Mechanical Design
Base on the RF design, cryostat design and experience, we make the mechanical design.
3D Model
Engineering drawing

9. Engineering Drawing – Details
Doorknob
Warm window
Pump
Low vac
Connect to cavity
Cold window
High vac
Connect to cryostat
70K 5K

10. Fabrication Progress Manufacturer: IHEP Experiment Factory.
The fabrication started in June 2010.
The work finished:
Parts machining;
Ceramic cold-shock test;
Copper plating & brazing test;
The work is being done:
Parts cleaning;
TIG welding;
Copper plating;
TiN coating;
Brazing;

11. Parts Machining – Doorknob
Finish machining;
Waiting for cleaning, TIG welding and brazing.

12. Parts Machining – Window
Finish machining;
Waiting for cleaning and brazing.
Cold window parts
Warm window parts

13. Parts Machining – Coaxial
Finish Parts machining;
Waiting for cleaning, TIG welding, copper plating and brazing.

14. Ceramic Brazing After ceramic brazing;
Waiting for TiN coating, being brazed with other parts;
Brazing

15. Ceramic Cold Shock Testing
The cold window works under 80K temperature, it is need to do cold shock test;
Test 99.5% and 97% alumina disk, 2 pieces for each;
The test procedure:
Cover the ceramic disks by Aluminium foil;
Put them in liquid Nitrogen;
After cooled down, take them out to room temperature;
Repeat for 3 times.
Uncover and watch it, make sure there is no crack.
No crack was noticed on all ceramic disks.

16. Ceramic Cold Shock Testing
Ceramic cooled by liquid N2
Put ceramic in liquid N2
After taking them out

17. Bellow Plating And Brazing Test
We are poorly experienced in copper plating on bellow, so the plating and brazing test was necessary.
The bellow before plating
The bellow after plating

18. Bellow Plating Test – Detail
There are some places missing plating
There are some bubbles on small bellow surface after heat treatment in H2 furnace

19. Bellow Plating Test
For the test result not good, the bellow was plated by another manufacturer;
The new result looks good, but the copper volatilized in H2 furnace, we think the reason is the thickness is too small;
The plating test will be tried again.

20. Bellow Brazing Test
Use plated bellow for brazing test, there is no leak in brazing joint;
The manufacturer want to use brazing in bellow connecting.
Brazing joint

21. The Works Are Being Done
TIG welding – connecting flanges;
Copper plating – bellow, coaxial conductor, etc;
TiN coating – on ceramic surface;
Brazing – window and coaxial conductor;
The works above will be finished at the beginning of next year.

22. Summary
We confirmed the RF design and made the mechanical design, and have begun the fabrication;
The machining of coupler parts has been finished, and the technical test are being done ;
The coupler brazing and assembling will be completed at the beginning of next year.

23. THANK YOU