1. THERMAL CYCLE TESTS OF RF WINDOWS IN STF INPUT COUPLERS 2010/12/07 Masato Satoh (KEK) 1

2. CONTENTS STF-1 （ Cryomodule tests with 4 cavities ） – Input coupler （ structure and specifications ） – Vacuum leak at low temperature S1-Global – Detail of vacuum leak(sniffer & color check) – Thermal cycle tests with sample windows Summary 2

3. STF-0.5, STF-1(2007 ～ 2008) STF-0.5(2007) : 1 cavity STF-1(2008) : 4 cavities S1-G(now on) ： 8 cavities 3 Cryomodule tests

4. STF-1: CM test for 4 cavities Cold window(80K) Cold Side Warm Side Input Coupler Nb-cavity 2.0K Warm window(300K) Input Coupler located from 300K to 2K supplies RF power into SC-cavities. Cross-section of CM 4

5. Input coupler Cold window 5E-7 Pa(IP) 1E-6 Pa Warm window Cold Window Coaxial ceramic disk Cu Brazing Between ceramics and Cu Choke ： To protect brazing part from strong electric field, and to match impedance at RF window Eacc = 31.5MV/m Beam current = 9mA Pin = 300 kW Input power in ILC Warm window Cold window 5

6. The cooling tests STF-0.5 : cryomodule tests for １ cavity – Cooling: 2007/10/3 ~ 2007/11/22 STF-1 : cryomodule tests for 4 cavities – 1 st cooling: 2008/5/21 ~ 2008/7/25 ２Ｋ Low power test – 2 nd cooling: 2008/9/9 ~ 2008/12/19 ２Ｋ High power test No.2 coupler ・・・ 3 thermal cycles No.1, No.3, No.4 couplers ・・・ 2 ones 6

7. Vacuum leak at cold windows Cold window : RT ～ 80K 3 couplers  vacuum leak 1 coupler  no leak Vacuum leak was caused by thermal cycles.  One potential reason might be bonded between different materials. 4 warm window at 300K occurred vacuum leak Warm WindowCold Window Pin :130~270kW(20~30MV/m) 2×1 0 -4 Pa m 3 /s 7

8. Confirmation of vacuum leak （ 1st : vacuum leak check ） Vacuum pump Leak detector 2 cold couplers were installed in vacuum chamber 8

9. Sniffer test （ｓｎｉｆｆ：嗅） φ6 No vacuum leak on outer brazing Vacuum leak on inner brazing for all the 3 couplers Scan pitch:3mm 0 deg Sensitivity:5E-8 Pam^3/s Cut down choke part 2.0E-04 Sniffer probe Result of sniffer check 9

10. Results of color check (No.1,No.3) No.1 CouplerNo.3 Coupler R12 C1 C2C2 There were color reactions and cracks ！ 65° 239° 10

11. L inear T hermal E xpansion C oefficient of Cu, Ceramics, Mo Cu pipe can absorb the thermal strain ! 11 16.6×10 -3 7.46×10 -3 5.39×10 -3 0.65×10 -3 2.7×10 -3 0.89×10 -3 Actual shrinking amount : - Δ length=length× ∫ LTEC dT The original was designed by Noguchi san and Toshiba. Cool down  OKThermal cycles  NG Some measures against the thermal strain

12. Mo -Ring （ Toshiba ） 300K1200K300K1200K  300K Cu Al2O3 Cu Al2O3 Cu Mo To reduce the strain of different material bonding It was developed for Tristan input couplers in 1988 Mo-ring is brazed with ceramic disk at the same time Al2O3 12

13. Need to improve inner brazing  Sample windows #1,#2 2009/Sep. ～ Oct. (S1-G already running) #2#1 Mo-ring （ t1.0 ） Stress ∝（厚度） ３  Ratio ３ ＝ 0.8 ３ ～ 0.5 ： to make stress half (ratio =0.8) The design was changed by Noguchi & Kako Cu-Pipe Sample windows 13

14. 300K  77K cooling process #2#1#1#1 41 5 6 2 3 #2 Indivisually put 3 TC on Samples 8 Leak Check after Cooling Thickly cover Samples by Al foil(16P) Temperature Change 14

15. Results of thermal cycles #1: Mo,0.25t #2: Mo,0.20t #3 and #4 same as #1 have been exposed in 22 thermal cycles  No vacuum leak Sample #1, #2 (2009 Sep ～ Oct) Sample #3, #4 (2010 Apr ～ Jun) Type-#1 was adopted in S1-Global 15

16. The improved ones are installed in S1-Global, and they have no trouble by now. 16

17. Summary STF-0.5&1 cryomodule tests were carried out, -Vacuum leak happened on 3 cold windows which had Cu Pipe= 1.0t, Mo = 0.25t Samples #1,#2 were made, and applied 6 thermal cycles - #1 Cu Pipe= 0.8t, Mo =0.25t had No vacuum leak Type-#1 was adopted for S1-G cryomodule test #2 Cu Pipe = 0.8t, Mo =0.20t happened Vacuum leak Sample #3, #4 same as #1  No vacuum leak against 22 thermal cycle tests 17