R&D for Fundamental Power Coupler in SRF Mass-Production Y. Yamamoto, E. Kako, T. Matsumoto, S. Michizono, H. Sakai, A. Yamamoto (KEK) C. Arcambal, E. Cenni (IRFU/CEA) Kirk FJPPL Workshop 2017 @Strasbourg

FJPPL Workshop 2017 @Strasbourg Outline Recent Large-scale SRF Accelerators Motivation (Goals for this R&D) R&D Items Summary FJPPL Workshop 2017 @Strasbourg

On-going Large-scale SRF Accelerators In recent years, SRF accelerator with several hundred cavities is standard in the world! Project Region Particle Beam energy RF # of cryomodules # of cavities / cryomodule # of cavities # of couplers E-XFEL EU Electron 17.5 GeV 1.3 GHz 101 8 808 LCLS-II U.S. 4 GeV 35 280 ESS Proton 2 GeV 352 MHz (Spoke) 704 MHz (Med., High) 13 9 21 2 4 26 36 84 Many R&Ds for cavity have been well-done, but as for power coupler, not so… ↓ We’d like to focus on power coupler, especially, for mass-production like ILC. FJPPL Workshop 2017 @Strasbourg

Goals for Power Coupler R&D Optimization in preparation/inspection works and RF conditioning method Rinsing procedure Ultrapure water rinsing Ultrasonic rinsing Ozonized (O3) water rinsing Inspection tools What tools we can use Full or Semi-automation? RF conditioning method How many steps for optimization? Which technical interlock system is used? Cost reduction TiN coating-free ceramic Lower cost design We’d like to fix the optimum method in each item! FJPPL Workshop 2017 @Strasbourg

Test Samples for Ceramic & Copper Plating φ19 x 3 (20 pieces) 100 x 50, 25μm (20 pieces) We already fabricated some test samples of ceramic and copper plating for the rinsing R&D. We will check the rinsing effect for various rinsing conditions. After that, we will try for power coupler similarly, and compare the RF conditioning time. FJPPL Workshop 2017 @Strasbourg

Test Power Couplers & Test Bench (TETD) Product No. Serial No. Ceramic company Ceramic color Ceramic coating Warm #1, #2 E42130 14L001 14L002 NGK/NTK White TiN Cold #1, #2 Cold #3, #4 14L003 14L004 KYOCERA Gray free Ceramic Ceramic Warm part Cold part The both inner surfaces are copper-plated. FJPPL Workshop 2017 @Strasbourg

Various rinsing procedures Ultrasonic rinsing in E-XFEL Ultrapure water rinsing in STF O3 water rinsing in Super-KEKB 1st step: To be done for test samples Surface inspection by microscope Measurement of secondary electron emission 2nd step: To be done for test power couplers Comparison of RF conditioning time Courtesy of Sakai-san in ARES group Courtesy of W. Kaabi FJPPL Workshop 2017 @Strasbourg

How to check rinsing effect Ceramic: Measurement for secondary electron emission coefficient Copper plating: Inspection by microscope Peeling test by 3M tape SEE measurement device C. Arcambal recommended this 3M tape! Courtesy of Hisamatsu-san FJPPL Workshop 2017 @Strasbourg

Inspection tools for copper plating Semi-automatic inspection system for cavity in STF We already developed the semi-automatic inspection system for cavity, but still not for power coupler. That is actually necessary for power coupler? Or, it is enough for the manual inspection? Digital borescope (J-SCOPE) Rigid borescope (OLYMPUS) Digital borescope (OLYMPUS) Courtesy of Takenaka-san FJPPL Workshop 2017 @Strasbourg Courtesy of Tanaka-san Courtesy of Higo-san

RF conditioning method E-XFEL STF Vacuum I/L: 1~2 x 10-4 Pa Arc I/L: Warm part & Waveguide Electron emission I/L: none Ceramic temperature I/L: none, but <50℃ How many steps for pulse width is necessary? Which technical I/L is necessary? How much is the threshold level? Courtesy of W. Kaabi FJPPL Workshop 2017 @Strasbourg

Power Coupler with TiN coating-free ceramic Unusual vacuum level in higher RF duty ↓ T-mapping attached Unusual heating in tapered section High power test was interrupted Particle simulation was done Secondary electrons can propagate to tapered section Ultrasonic rinsing will be done Material search restarts New coupler will be fabricated Made in KYOCERA LSEEC Electrical Property Volume Resistivity ohm･cm - Surface Resistivity ohm/□ 1.2 X 1014 SEE　Coefficient 3.2 Dielectric Constant 1MHz 8GHz 10.0 Dielectric Loss Angle 3 X 10-3 Many secondary electrons emitted from ceramic surface can propagate up to tapered section! FJPPL Workshop 2017 @Strasbourg PIC solver in CST

Enough budget for these R&Ds is expected in F.Y. 2018. Lower cost design Cost reduction is urgent issue for ILC! L. Evans There are two candidates for power coupler in ILC. How are they merged? Which design is lower cost? Enough budget for these R&Ds is expected in F.Y. 2018. FJPPL Workshop 2017 @Strasbourg

FJPPL Workshop 2017 @Strasbourg Summary Power coupler R&D for mass-production should be focused R&D for test samples is already starting New material for TiN coating-free ceramic is searching We will discuss the contents for this R&D during IPAC2017 in Copenhagen next week! FJPPL Workshop 2017 @Strasbourg