CEPC Cavity Helium Vessel and Tuner MI Zhenghui

CEPC Cavity Helium Vessel and Tuner MI Zhenghui mizh@ihep. ac. cn Institute of High Energy Physics(IHEP) 2018 -09

Outline p Background p Helium vessels for 650 MHz Cavity p Tuners for 650 MHz cavity p Summary

650 MHz 2 -cell Cavity n 650 MHz cavities for CEPC • There are two RF sections located at two long straight sections respectively, Each RF section contains two Collider RF stations RF station • 240 cavities for CEPC Collider • Each cryomodule contains six 650 MHz 2 -cell cavities Collider layout 650 MHz 2 -cell cavity and cryomodule n 650 MHz cavities for PAPS Beam test system 650 MHz cryomodule DC photo cathode gun CW 10 m. A, 50 Me. V Beam test system layout

Cavity string Beam Taper direct ion • The coupler is installed horizontally; HOM absorber • Coupler Tuner is installed at the end of Helium vessel; Gate valve Upstream cavity have one HOM coupler, in order to Gate valve reduce the kicker effect on HOM Coupler Physical dimension: • Tuner the beam

Helium Vessel 434. 5 mm LHe out port Bellow HOM port 450 mm Helium Vessel Pickup port Coupler port End stiffener LHe in port 650 MHz 2 -cell cavity + Helium Vessel 3 D module Stiffener Cross- section Transition ring End stiffener Holes for LHe in End stiffener

Endplate for Helium Vessel • FP Endgroup Welding with half cell adapter ring Welding with beam pipe Welding with HOM coupler port Welding with end stiffener Welding with transition ring

Endplate for Helium Vessel • MC Endgroup

Endplate for Helium Vessel • Endgroup to Dumbbell Electron-Beam Welding FP Endgroup MC Endgroup Dumbbell Assembly • Cavity is Ready Degassing/Annealing Process

Welding sequence for Helium Vessel • Helium vessel welding EBW EBW TIG 320 mm

Simulation • Bellows ① ② Fixed • ③ Fixed ① ② ③ T(K) Stress（MPa） 2 atm 0 atm 300 50 0 atm 2 atm 0 atm 300 262 df/dp and LFD df/dp(Hz/mbar) LFD(Hz/(MV/m)2) With vessel 8. 18 - 0. 29 Without vessel 5. 33 - 0. 3

Tuners for 650 MHz Coupler Main parameters of tuner HOM coupler Tuner Cavity + Coupler + HOM Coupler + Tuner • The space is tight due to the HOM coupler • The improved tuner from Saclay type tuner • Cavity will be stretched during tuner work Arm Eccentric shaft

Tuners for 650 MHz • Tuner design: Tuner 3 D model • Slow/Coarse Tuner is double lever tuner Eccentric shaft • Coarse Tuner ration ＞ 1: 10 • Fast Tuner – two Piezo installed at the same side Limit screw m Displacement sensor Lever Ar Piezo Motor Shaft Support Limit switch Limit screw Pick up HOM Coupler

Tuners for 650 MHz • Tuner design: Tuner 3 D model F Special-shaped flange Push cavity flange

Tuners for 650 MHz • Restraining “Safety” Brackets System • Design of the Tuner and restrained brackets included requirements to protect cavity during all steps. auxiliary fixture • Cavity will be always in elastic region. • Clean-room requirements • Impact of remnant magnetic field from the safety brackets on the cavity Q 0 must be minimum Limit screw • Remove the auxiliary fixture after the cavity string outside the cleanroom; • Install the tuner and adjust the limit screw

Maintenance ports for Tuner Piezo Motor

Summary • Helium Vessel • Square end plate is used for the Helium Vessel, which don’t need molds and stamping; • End stiffener as parts of the Helium Vessel; • The Helium Vessel welding with EBW; • The Bellows welding with TIG; • Tuner • Two lever arm type tuner is used due to the installed space is tight; • Eccentric shaft is used for the tuner; • Safety Brackets System, limit screw and limit sensors are installed; • The materials for the tuner are TA 3 and 316 L to reduce the weight ; • Tuner maintenance ports is on the opposite of MC coupler；

Thank you for your attention！