RD for Fundamental Power Coupler in SRF MassProduction

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) FJPPL Workshop 2017 @Strasbourg Kirk 1

Outline u Recent Large-scale SRF Accelerators u Motivation (Goals for this R&D) u R&D Items u Summary FJPPL Workshop 2017 @Strasbourg 2

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 E-XFEL EU Electron 17. 5 Ge. V 1. 3 GHz 101 8 808 LCLS-II U. S. Electron 4 Ge. V 1. 3 GHz 35 8 280 EU 2 Ge. V 352 MHz (Spoke) 704 MHz (Med. , High) 13 9 21 2 4 4 26 36 84 ESS Proton RF # of cryomodules # of cavities / cryomodule # of cavities # of couplers 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 3

Goals for Power Coupler R&D u Optimization in preparation/inspection works and RF conditioning method u Rinsing procedure u Ultrapure water rinsing u Ultrasonic rinsing u Ozonized (O 3) water rinsing u Inspection tools We’d like to fix the optimum method in each item! u What tools we can use u Full or Semi-automation? u RF conditioning method u How many steps for optimization? u Which technical interlock system is used? u Cost reduction u Ti. N coating-free ceramic u Lower cost design FJPPL Workshop 2017 @Strasbourg 4

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 5

Test Power Couplers & Test Bench Coupler (TETD) Product No. Serial No. Ceramic company Ceramic color Ceramic coating Warm #1, #2 E 42130 14 L 001 14 L 002 NGK/NTK White Ti. N Cold #3, #4 E 42130 14 L 003 14 L 004 KYOCERA Gray free Ceramic Warm part Cold part The both inner surfaces are copper-plated. FJPPL Workshop 2017 @Strasbourg 6

Various rinsing procedures Ultrasonic rinsing in E-XFEL Ultrapure water rinsing in STF O 3 water rinsing in Super-KEKB Ø 1 st step: To be done for test samples Courtesy of Sakai-san in ARES group Ø Surface inspection by microscope Ø Measurement of secondary electron emission Ø 2 nd step: To be done for test power couplers Ø Comparison of RF conditioning time Courtesy of W. Kaabi FJPPL Workshop 2017 @Strasbourg 7

How to check rinsing effect Ceramic: Measurement for secondary electron emission coefficient SEE measurement device Courtesy of Hisamatsu-san Copper plating: Inspection by microscope Peeling test by 3 M tape FJPPL Workshop 2017 @Strasbourg C. Arcambal recommended this 3 M tape! 8

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? ØDigital borescope (J-SCOPE) ØRigid borescope (OLYMPUS) ØDigital borescope (OLYMPUS) Courtesy of Takenaka-san Courtesy of Higo-san FJPPL Workshop 2017 @Strasbourg Courtesy of Tanaka-san 9

RF conditioning method E-XFEL STF ü ü Courtesy of W. Kaabi 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℃ p How many steps for pulse width is necessary? p Which technical I/L is necessary? p How much is the threshold level? FJPPL Workshop 2017 @Strasbourg 10

Power Coupler with Ti. N coating-free ceramic Made in KYOCERA Electrical Property LSEEC Volume Resistivity ohm･cm - Surface Resistivity ohm/□ 1. 2 X 1014 SEE　Coefficient - 3. 2 1 MHz - - 8 GHz - 10. 0 1 MHz - - 8 GHz - 3 X 10 -3 Dielectric Constant Dielectric Loss Angle 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 Many secondary electrons emitted from ceramic surface can propagate up to tapered section! FJPPL Workshop 2017 @Strasbourg PIC solver in CST 11

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 12

Summary p Power coupler R&D for mass-production should be focused p R&D for test samples is already starting p New material for Ti. N coating-free ceramic is searching We will discuss the contents for this R&D during IPAC 2017 in Copenhagen next week! FJPPL Workshop 2017 @Strasbourg 13