3.9GHz Coupler Cold End Robustness Study Will Couplers survive on-site and overseas shipping? D. Olis, G. Galasso, M. McGee

The Coupler Cold End Outer Conductor / Warm End Waveguide

Final Assy. of couplers

Coupler installed on the test stand support

Ship w/ Cold Coupler Only Protect Cold End ceramic with cap. Without support of 80K flange during shipping, Cold End is cantilevered on cavity –This is a load on the cavity flange. Excessive? –Perhaps design a soft connection between coupler and vacuum vessel to damp motion of Cold End to protect cavity.

Transporting Cryomodules Cryomodule shipping options: 1.Ship individual components, assemble & align at final use point 2.Ship assembled cavity string, complete assembly and alignment at final use point 3.Ship assembled and aligned cryomodule In all cases, coupler antenna tip is unsupported. Will shipping loads & vibrations cause undue stress on ceramic window, copper collars, or antenna?

Cold End Assembly Cold End ceramic window

Failure Modes Will ceramic RF window fracture or develop a leak? Will antenna position move off center axis?

The first “test”: delivery from CPI. Good news: couplers survived shipment from vendor (domestic: Boston to Fermi). ~1dozen 1.3GHz TTF3 couplers have been shipped from DESY to Fermi (same ceramic design).

Study Plan FEA and hand calc’s using g-loads recorded during shipping of cavities between DESY and Fermilab Mechanical tests –Simple harmonic and drop test.

FEA Results (M. McGee, G. Galasso) Load = 1G from earth + 6G shocks Above: antenna (316L SS) max stress is 700PSI. Left: cold window (97% alumina) max stress is 550PSI. Stress is the same at interface with OFHC copper collars. These are pretty darn small!

ItemMat’l Predicted Stress [KSI] Yield Strength [KSI] Ultimate Strength [KSI] Endurance Limit [KSI] Antenna 316L stainless Collars OFHC copper RF window 97% alumina G loads well below allowable limits

Ansys: 0.12 mm tip of the antenna Static analysis. Load: acceleration 11G Maximum displacement Comsol: 0.11 mm tip of the antenna FEA by G. Galasso

mm mm mm Static analysis. Load: acceleration 11G Maximum displacement review Conclusion: Do NOT attempt to damp this end of Cold coupler. It could do harm without any benefit.

Window Brittle Failure Analysis At 550PSI stress, minimum crack length in alumina that results in catastrophic failure is 21.3 inches. –Window will not fail suddenly due to 6G shock At +/- 550PSI alternating stresses, any existing micro-cracks will not grow. –Window will not fail in fatigue due to 6G cyclic loads

Test Plan Load plan –Vibration analysis –Drop/shock tests Instrumentation –Accelerometers Measurements, before & after sdrop test –Leak check, CMM

Vibration Test To confirm harmonic characteristics

Modal Freq. [Hz] AnsysComsol 1 st nd rd rd 2nd 1st Real test. Impulse Response FE Model Modal Analysis Analysis by G. Galasso

Frequency Response. Load: 1 st mode Results in the frequency range 190 Hz<first natural Freq< 210 Hz ξ =0.005 Typically for metals like Stainless Steel: 0.01<ξ<0.005 Von Mises Stress [MPa] vs. Frequency antenna 67MPa/9.7ksi 200 Hz 8MPa/1.1ksi 200 Hz Von Mises Stress vs. frequency Copper-ceramic interface Analysis by G. Galasso

ItemMat’lPredicted Stress [ksi] Yield Strength [ksi] Displace- ment [mm] Antenna316L SS CollarsOFCH Copper Window97% Alumina (Ultim. Str.) Frequency Response. Load: 1 st mode Review Worst case considered: 1 st modal frequency range (190Hz-210Hz) Damping factor

Cold End Coupler drop test Test Coupler is simplified:  Window, 4.5”CF flange, antenna, and window  No copper plating  Instrumentation, inspection of antenna is easier Test Piece Input coupler

Drop Test plan Incremental increase in G-load until failure Leak check and CMM measurement between increments. Brazed assemblies to be rec’d in early January.