Performance Degradation in STF Cryomodules from STF-1 to STF-2 Kirk 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

WG1 in TTC Meeting 2016 @Saclay Outline STF Cryomodules Performance Degradation Consideration of Causes for Degradation Consideration of Another Cause for Degradation Summary 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

STF Cryomodules 4 cavities per batch STF Cavity Package 5/Jul/2016 STF-1 (4 cavities) in 2008 S1-Global (4+4 cavities) in 2010 4 cavities per batch Proc. in SRF2011 Proc. in SRF2009 STF-2 (12 cavities) in 2014~ STF Cavity Package Quantum Beam (2 cavities) in 2012 Capture CM in STF-2 accelerator Proc. in IPAC12 WEPMB017 in IPAC16 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

Performance Degradation Statistics for cavity performance; Above 31.5 MV/m: 11 cavities Degradation: 4 cavities Three types of performance limit; One cavity: Quench w/o F.E. Two cavities: F.E. Quench One cavity: Quench by enormous heat loss Three degraded cavities in STF-2 are connected in series.  Common cause for degradation Q0 measurement is not done yet in STF-2. It will start from this autumn. Heavy F.E. in V.T. 22 cavities in 6 cavity strings Statistics for cavity string (four cavities per batch); Four cavity strings: No degradation Quantum Beam: Degradation, but around ILC spec. CM-1b in STF-2: Significant degradation 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

Cavity string/Beam pipe connection in Tunnel Local clean booth Ion pump Ion pump Three degraded cavities in series Use of simply local clean booth Local clean booth was used for four beampipe connection parts Exchange of metal valve near cavity string #2 Metal valve was a little bit bigger, disturbed thermal shield attachment Extra Argon gas purging at gate valve opened Usually, when gate valve opens, both sides should be under vacuum but, we had to do Argon gas purging for the both sides due to complicated process of cryomodule assembly A little bit bigger metal valve 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

Improvement of clean room items Many experiences in EU-XFEL High quality local clean booth Slow pumping system High quality particle counter Will be introduced in 2017(?) 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

Method of RF Conditioning in 2K Cavity conditioning is done very carefully as monitoring HOM heating, unusual RF output from HOM, and X-rays. When heating, unusual output or x-rays appear, we have to keep the gradient level for a while. After processing out, we can go to next level. RF parameters in STF-2 QL : 5.0 x 106 Filling time : 900μsec Flat-top : 800(100)μsec Total width : 1700μsec Temp. sensor at HOM coupler Summary of cavity conditioning time in 2K Conditioning time was too short? 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

Consideration of Another cause Never changed after V.T. 661 Cavity data in EU-XFEL Both Kt in V.T. and M.T. should be same, but… 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

Change of Kt in EU-XFEL WEPMB007 in IPAC16 Grey zone When Kt changes from V.T. to M.T., Eacc at performance limit also changes? ↓ If so, this effect is independent of performance degradation! 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

WG1 in TTC Meeting 2016 @Saclay Summary Four degraded cavities in STF One cavity: Capture CM, three cavities: STF-2 CM-1b Cavity string/beampipe connection has to be improved RF conditioning time is possibly effective for degradation Change of Kt also has to be considered 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

WG1 in TTC Meeting 2016 @Saclay Back-up slides 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

Cavity performance in CM1/CM2a Module # CM1 CM2a String # 1 2 3 Cavity # 4 5 6 7 8 9 10 11 12 Cavity name MHI-14 MHI-15 MHI-17 MHI-18 MHI-19 MHI-20 MHI-21 MHI-22 MHI-24 MHI-23 MHI-25 MHI-26 Eacc @V.T. [MV/m] >36.6 (power limit) 35.7 (Cell#1 Quench) >38.4 >36.2 37.2 >35.1 >38.9 >35.8 >12.0 (admin. stop) 35.9 (Cell#3 Quench) 32.3 31.6 Eacc @C.T. (short pulse) >38.6 36.8 (Quench) 35.2 >36.1 (Pf max.) 26.6 20.0 25.0 >18.0 33.6 32.1 31.5 (full pulse) >38.7 36.7 35.3 >36.3 >26.0 16.4 24.6 >32.3 >18.1 34.1 33.2 32.4 Rad. Level in V.T. @31.5MV/m [μSv/h] 0.0 110 15 0.4 0.3 10.2 15800 >100000@12.0MV/m 40 0.2 4380 Rad. Level in V.T. @35.0MV/m [μSv/h] 740 193 1.8 48 207 70400 300 2.5@ 32.3MV/m 4840@ 31.6MV/m Rad. Level in C.T. @31.5MV/m [μSv/h] 8.7 82.4 10.1 151.9 605 @26.4MV/m (short pulse) 117 @20.0MV/m (short pulse) 228 @24.6MV/m (short pulse) 869 9700 @18.0MV/m (short pulse) 176 158 10400 Rad. Level in C.T. @35.0MV/m [μSv/h] 150 239 24 638 5110 @26.0MV/m 0.0 @16.4MV/m 444 @24.5MV/m 996 @32.3MV/m 21000 @18.1MV/m 315 @34.1MV/m 168 @33.2MV/m 11000 @32.0MV/m ※縦測定でのpower limitは入力が250Wを超えた、という意味である ※モジュール試験でのadmin. stopは諸々の状況を見て途中で測定を中断した、という意味である 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

Summary of radiation level in CM test Short pulse (900+100μsec) Full pulse (900+800μsec) 空洞直下で測定した放射線量の比較(ただしCavity#10以降は固定)。 Radiation level is measured below the cavity, upstream and downstream of beampipe. Field emission is observed for every cavity. Especially, cavity #5, #6, #7 and #9 had heavy F.E. There was no radiation in full pulse mode for Cavity #6. Because, Cavity #6 was limited by HOM heating before field emission. But, as you see the short pulse mode, it was comparable with Cavity #5 and #7. MAR-781/-782 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

RF output from HOM couplers Eacc Pin HOM #2 Cavity#6 (MHI-20), short pulse @2015/11/5 2つのHOMカプラからのRF出力を検波器を 通した後でオシロに繋いでモニターした結果、 発熱と同時に異常な信号が出ているのが観測 された。これは、片側からのみ出る場合も あれば両方同時に出る場合もあり、また、 出てくるタイミングもまちまちであった。 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

RF output from HOM couplers Eacc Pin HOM #2 Cavity#10 (MHI-24), short pulse @2015/11/13 別の空洞の例。1パルス内の別のタイミングで それぞれ出現する場合もある。これらの異常 信号は発熱の頻度の低下と共に収まっていく 傾向がある。HOMカプラは縦測定ではほとんどエージングされないため、モジュール試験では時間をかけてエージングする必要がある。 DESYのXFELではどうしているか興味深い。 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

RF output from HOM couplers Cavity#3 (MHI-17), short pulse @20.0MV/m Cavity#7 (MHI-21), short pulse @6.0MV/m Cavity#7 (MHI-21), short pulse @13.0MV/m Ch.1 : Pin Ch.2 : Pref Ch.3 : electron (peak) Ch.4 : electron (integration) Ch.5 : Arc Ch.6 : Gradient Ch.9 : RF output from HOM#1 Ch.10 : RF output from HOM#2 Cavity#8 (MHI-22), short pulse @12.0MV/m Cavity#9 (MHI-24), short pulse @13.0MV/m 別なオシロのデータ。 通常のHOM出力の何桁も大きな信号が出ているのが分かる。 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

Positions of radiation detector never moved downstream upstream Monitors at ground level never moved MAR-782 CM2a MHI-26 MHI-25 MHI-23 CM1 MHI-24 never moved MHI-22 MHI-21 MHI-20 MHI-19 MAR-781/-782 MHI-18 MHI-17 MHI-15 MHI-14 cavity MAR-781 Injector CM The cable length is different between MAR-781 and MAR-782. MAR-781 is shorter, and then could not be put at the end of CM2a. MHI-13 MHI-12 MAR-781/-782 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

Positions of radiation detector in CM2a cavity MAR-782 never moved downstream CM2a MAR-782 MHI-26 upstream never moved MHI-25 MHI-23 CM1 MHI-24 never moved MHI-22 MHI-21 MHI-20 MHI-19 MHI-18 MHI-17 MAR-781/-782 MHI-15 MHI-14 cavity MAR-781 Injector CM never moved For MHI-23, -25 and -26, MAR-781 is not the position below the cavity. MHI-13 MHI-12 MAR-781 Cavity#10以降の高感度モニターはケーブル長が足りないため空洞直下に設置できなかった。 同様に、下流側の高感度モニターもモジュール設置用の台座に設置せざるを得なかった。 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay

WG1 in TTC Meeting 2016 @Saclay Change of Kt in STF During jointing helium tank after V.T., these cavities in STF-2 were deformed? 5/Jul/2016 WG1 in TTC Meeting 2016 @Saclay