CEPC Input Coupler Discuss 6th IHEP-KEK SCRF Collaboration Meeting Ma Q., Huang T.M. 2017-7-14

Index Requirement of CEPC FPC Concept design of 650MHz Coupler Design of 1.3GHz Coupler

Requirements of CEPC FPC Main ring Booster Frequency (GHz) 0.65 1.3 Power (kW) 300 (400 update?) 10 Coupling (Qext) Variable: 1E5~2E6 Variable: 4E6~4E7 2 K heat load (dynamic300kW,TW,CW) 1 W 0.3 W Assembly Clean assembly of coupler to cavity in class 10 clean room

Concept design of 650MHz coupler The length of coupler in the cryomodule Variable coupling Change outer conductor length Change inner conductor length Change inner conductor length, Bellow on 1/4 λ shorter port ( LHC Type ) Single window or Double windows

Concept design of 650MHz coupler The length of coupler in the cryomodule As the inner diameter is 1300, the length of coupler (window and vacuum coax ) is less than 460. The short vacuum coax line leads the difficulty of heat- load controling. If use the rectangular module, the length of coupler is not a problem. Maybe it's a another choice. FPC coupler port Beam Pipe cryomodule inner surface

Variable coupling Usually,Changing the penetration depth of the antenna tip to adjust the Qext. Calculation shows the length of change is about 30mm.

Variable coupling Change outer conductor length, like TTF coupler. TTF-III coupler

Variable coupling Move the window to change the outer conductor length. Bellow needs special cooling. otherwise the temperature will be over 400K. Remove the length of window (~120) and bellow(~220), the length of coax line is too short for heat insulation(<120). This design need fatter cryomodule or rectanglar crymodule. fixed by WG window water cooling bellow fixed by Cavity move window 5K 80K 300K

Variable coupling Change inner conductor length, like ATF coupler or KEK-STF coupler . ATF coupler STF coupler

Variable coupling Add bellow on inner conductor. Bellow cooling: water or air? Water cooling: bellow corrosion by water? air: insufficient cooling? Easier heat load control. Need more heat simulation. window Bellow coolingpipe move antenna tip 5K 80K 300K

Variable coupling Change inner conductor length, Bellow on 1/4 λ shorter port ( LHC Type ) The ONLY variable coupler operating above 300kW CW in the world. LHC Type need rectanglar Cryomodule. It is a future design or not? LHC coupler

Single window or Double windows Avoid polution when ceramic was broken. Expensive. More complex, more trip rate. Single window Maybe 1~3 module were poluted when ceramic was broken. And long period was spent for changing the module. Cheaper and simpler.

Single window or Double windows transmission line waveguide win Vacuum transmission line warm win Difficult to cooling in big CW power cold win win Cavity Cavity X ?

Collabration of 650MHz Coupler Collabration on concept design and simulation.

Design of 1.3GHz Coupler Finished the RF design and mechanical rough design. Doing heat simulation now. RF model of CEPC booster cavity FPC

Collabration of 1.3GHz Coupler Collabration on design and Power test. Hope to test the coupler in KEK in late 2018. Prepare the coupler and vacuum connect waveguide( if the connect flange is not same ) (IHEP) Prepare the power source, low level controller and interlock system (KEK) The details of test could be discussed later.

Thanks