SNS Coupler Shipping Plans J. Mammosser, S. Stewart, B. Degraff , R. Huerto, Y. Kang, M. Howell

Overview: The Proton Power Upgrade (PPU) project is under way at SNS SNS will process all RF couplers for the 7 new cryomodules that will be assembled at JLab SNS will be responsible for the shipping of 15 pairs of conditioned RF couplers to Jlab for CM assembly

Current Status: CD1,3a has been awarded 30 new PPU couplers were procured (Jan 2019) Couplers will be shipped to SNS starting in 6 months from now SNS will clean, assemble, bake and condition these couplers and ship them to Jlab Developing the shipment methodology is underway Some design changes were made to the coupler design for PPU Additional weight of the center conductor (~ 700g )

PPU Performance Requirements Parameters Original SNS high-beta Cryomodule design PPU high-beta cryomodule requirements Eacc (MV/m) (=EoTg, Tg: Transit time factor at β=0.81) 15.8 16.0* Fundamental Power Coupler (FPC) Rating (kW): peak and avg. 550, 50 700, 65* External Q of fixed FPC 7 X105 ± 20% 8 X105 ± 20% Cavity Material High RRR niobium cells Reactor grade end groups High RRR for cell and end groups Higher-order Mode Couplers (2) one at each end group None* Helium Vessel Good engineering practice Modified for code requirements* *Operationally demonstrated in SNS RRR = Residual resistivity ratio

Design Changes - FPCs Charge 2 Two minor changes for the fabrication of new FPCs The Inner Conductor wall thickness will increase from 3.5 mm to 7.5 mm to keep an operating temperature below the ones currently in operation Increase of weight of inner conductor by ~700 g The Center Conductor Length will be reduced by 1.5 mm (302.5mm tip to flange face) to increase the Qext

Shipping of Couplers After Conditioning Current plans are to ship conditioned couplers on their bridge waveguide After conditioning: A leak check will be performed on the bake cart Then an isolation valve will be closed on the bake cart and couplers will be transfer to a shipping cart Vacuum space will then be vented to 2 psig nitrogen gas and isolated Couplers will have full instrumentation for installation in string assembly Once arriving at Jlab, the vacuum space will be pumped out and leak checked

Coupler assembly configuration

Coupler bridge waveguide

Bake Cart Configuration

Current Coupler Shipping Concept: Coupler center conductor will be rigidly connected to the outer conductor with a plate bolted to both This should minimize movement of the center conductor and prevent stress on the ceramic Additional absorbing material on the air side will be investigated as well Coupler will be shipped under nitrogen pressure (2psig) Coupler cart will be similar in design to cleanroom cart and hold one bridge waveguide/ 2 RF couplers FedX white glove van delivery service will be used Two carts/ 4 couplers will be delivered at one time to JLab

RF Coupler Conditioning Assembly

Shipping Configuration Stiffening Plate Shipping Configuration Absorption Material Option

Coupler Shipping Test Plan: Coupler modes were modeled Two PPU style RF couplers will be: Cleaned and assembled Baked RF Conditioned and Leak checked Vented to 2 psig nitrogen Shipped to Jlab and back to SNS Pumped and Leak checked RF conditioned again Vibration data will be collected

Conclusion: The PPU project at SNS is underway 30 new high power couplers will be conditioned and shipped to Jlab for assembly into 7 new cryomodules Discussions on shipping of conditioned couplers to avoid damage is underway Current plans are to ship coupler: Mounted on bridge waveguide in pairs Stiffening the mechanical system with a plate connecting the inner and outer conductors Shipping under 2 psig nitrogen pressure