VERTICAL TEST RESULTS OF SPOKE RESONATOR AT IPNO

OUTLINE ESS Spoke Resonator ESS Project MYRRHA Project Double Spoke resonator presentation Cavity preparation and test configuration Results of tests 2 prototypes from Zanon 1 prototype from SDMS MYRRHA Project Simple Spoke resonator presentation Vertical test configuration

RAPPEL TITRE PRESENTATION mardi 31 juillet 2018 4 HPR Ports Pick-up Port ESS Spoke Resonator E field Lorentz detuning : Simulated : -5.5 Hz/(MV/m)2 Measured : -6.8 Hz/(MV/m)2 Pressure sensitivity : Measured : 24.3 Hz/mbar DOUBLE-SPOKE CAVITY Frequency [MHz] 352.21 Beta_optimum 0.50 Operating gradient [MV/m] 9.0 Temperature (K) 2 Bpk [mT] 62 Epk [MV/m] 39 G [Ohm] 130 r/Q [Ohm] 426 Lacc (=beta optimal x nb of gaps x λ /2) [m] 0.639 Bpk/Eacc [mT/MV/m] 6.88 Epk/Eacc 4.34 P max [kW] 335 Coupler port Stiffeners H field

Test configuration ESS Spoke Resonator Cavity preparation Ultra-sonic degreasing Etching of 200 µm (goal) Phase 1: Horizontal, 120 minutes Phase 2: Horizontal (180° rotation), 120 minutes Phase 3: Vertical, 240 minutes 2 barrels to limit acid temperature < 18°C Cold water in helium tank HPR : 12h 6 ports (2 beam tubes, 4 HPR ports) 24h drying Vertical test done « in vertical ». Cooling is not optimal : gas pocket ESS Spoke Resonator

Tests results : ROMEA ESS Spoke Resonator 6h at 100K Bad Baking ??

Tests results : ROMEA ESS Spoke Resonator Bad Baking ??

Tests results : ROMEA ESS Spoke Resonator 30 microns BCP

Tests results : ROMEA ESS Spoke Resonator Room temperature cycle +cavity opened + HPR

Tests results : Giulietta ESS Spoke Resonator Bad Baking again ??

Tests results : Giulietta ESS Spoke Resonator Additional etching Baking 3 Fast Room temperature cycle 1 4 2

Conclusions ESS Spoke Resonator Q-disease not dissolved at room temperature ? Possible if hydrogen concentration high enough ? Or surface is damaged by precipitation ? Presence of skeletons But nothing observed with confocal microscope on Niobium samples placed on a cavity during a test See : Advances in SRF Material Science aimed at High Q cavities. A. Grasselino SRF Development Department, TD Fermilab NA-PAC 2013 Pasadena, California

Conclusions ESS Spoke Resonator Why never observed on Spiral2 QWR ? Same facilities (BCP, HPR) Same Niobium (Tokyo Denkai) Hydrogen degassing is compulsory for ESS cavities New furnace at IPNO

RAPPEL TITRE PRESENTATION mardi 31 juillet 2018 MYRRHA Spoke Resonator E field Lorentz detuning : Simulated : -5.5Hz/(MV/m)2 Measured : -8.2 Hz/(MV/m)2 Pressure sensitivity : Simulated : 11 Hz/mbar Measured : 236 Hz/mbar H field

MYRRHA Spoke Resonator Test configuration MYRRHA Spoke Resonator Cavity preparation Ultra-sonic degreasing Etching of 200 µm (goal) (~ 0.4 µm/min) Phase 1: Horizontal, 200 minutes Phase 2: Horizontal (180° rotation), 100 minutes Phase 3: Same position but fresh acid, 100 minutes 2 barrels to limit acid temperature < 18°C Cold water in helium tank HPR : 4 ports (2 beam tubes, 2 coupler ports) 48h drying Vertical test done « in horizontal ». Amélia : tested with helium tank Virginia : cavity fully immersed in helium (dunk test)

MYRRHA Spoke Resonator Tests results : Amélia MYRRHA Spoke Resonator Test with helium tank Quench BCP : ~ 300 µm

Tests results : Virginia MYRRHA Spoke Resonator Dunk test BCP : ~ 150 µm

MYRRHA Spoke Resonator Conclusions MYRRHA Spoke Resonator Q-disease test not performed yet on MYRRHA cavities Strong Q-slope on both cavities Probably hydrogen contamination Hydrogen degassing will be tested this year 650°C with Ti tank