1.3GHz Input Coupler for ILC

IHEP RF

Outline • Design

– The major results of simulation calculation (review)

– The mechanical design

• Fabrication– Have been done

– To be done

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.

Coupler Specification

Frequency 1.3 GHz

PowerTest: 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

Cold part Warm part

Doorknob

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.

Power Transmission Performance

1.1 1.2 1.3 1.4 1.50.0

0.2

0.4

0.6

0.8

1.0

Ma

g(S

21

)

Frequency (GHz)

Before optimize After optimizeMesh check

The |S21| frequency sweep curve describes the power transmission performance: Mag(S21)= 0.9974@1.3GHz shows a good RF structure design from the view of power transmission. Passband: 200MHz when VSWR<1.1; 250MHz when VSWR<1.2

0.9974@1.3GHz

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 c

oupler port center D=60mm, adjust the antenna penetration near 8mm;

D

H R_tip

Qext change VS antenna penet rat i on depth

0. 000E+001. 000E+062. 000E+063. 000E+064. 000E+065. 000E+066. 000E+067. 000E+06

0 2 4 6 8 10

Antenna penet rat i on depth(mm)

Qext

D=55 mmD=60 mm

Mechanical Design• Base on the RF design, cryostat design

and experience, we make the mechanical design.

3D Model3D Model

Engineering drawing

Engineering Drawing – Details

DoorknobWarm window

PumpLow vac

Connect to cavity

Cold window

PumpHigh vac

Connect to cryostat70K5K

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;

Parts Machining – Doorknob• Finish

machining;

• Waiting for cleaning, TIG welding and brazing.

Parts Machining – Window

• Finish machining;

• Waiting for cleaning and brazing.

Cold window parts

Warm window parts

Parts Machining – Coaxial

• Finish Parts machining;

• Waiting for cleaning, TIG welding, copper plating and brazing.

Ceramic Brazing

• After ceramic brazing;

• Waiting for TiN coating, being brazed with other parts;

Brazing

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.

Ceramic Cold Shock Testing

Put ceramic in liquid N2

Ceramic cooled by liquid N2

After taking them out

Bellow Plating And Brazing Test• We are poorly experienced in copper

plating on bellow, so the plating and brazing test was necessary.

The bellow after platingThe bellow before plating

Bellow Plating Test – Detail

There are some bubbles on small bellow surface after heat treatment in H2 furnace

There are some places missing plating

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.

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

The Works Are Being Done• TIG welding – connecting flanges;• Copper plating – bellow, coaxial conductor, e

tc;• TiN coating – on ceramic surface;• Brazing – window and coaxial conductor;• The works above will be finished at the begin

ning of next year.

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.

THANK YOU

2010-12-7