CW accelerating module test progress at DESY TESLA Technology Collaboration (TTC) Meeting, Milano. Denis Kostin, Jacek Sekutowicz February 6th, 2018

Outline Cryo Module Test Bench (CMTB) at DESY; CW Module Test Milestones; CW Module Test Progress; Pulsed Module Test Update; CW Module Test Operation; Conclusion. | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018

Cryo Module Test Bench (CMTB) at DESY first dedicated accelerating module test stand at DESY – now in CW operation | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018

CW Module Test Milestones XM-3 module test data for CW and long pulse mode XM-3 has been tested also in CW and long pulse (LP) mode, with pulse lengths up to 520 ms and repetition rate of 1 Hz. The highest gradient for LP mode was 20.1 MV/m with DF=43.2%. Q0 measured in the SP/ LP/CW operation modes at 1.8K and 2K. SP operation possible up to at least 25 MV/m. At 24 MV/m Q0 ≳ 2×1010@2K in SP operation mode was measured. For LP operation at ca. 15 MV/m, Q0=4.1×1010 @ 1.8K was achieved. Reached Vector Sum (VS) amplitude stability ~ 10-4, phase stability 10 mdeg. temperature short pulse (SP) long pulse (LP) CW 1.8 K Q0 = 4.1×1010 14.7MV/m, DF=20% Q0 = 4.7×1010 9.5MV/m 2.0 K Q0 = 2.0×1010 24 MV/m, DF=1% Q0 = 2.1×1010 20.1MV/m, DF=43% Q0 = 2.3×1010 17.2 MV/m | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018

CW Module Test Milestones Module XM-3 CW and LP mode measured points | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018

CW Module Test Progress recent changes and plans Module XM-3 power couplers were better mechanically adapted to CW operation and higher Qload by shifting the outer isolation vacuum flanges by 10 mm outwards, thus shifting the actuators and antennae moving range. This way higher maximum Qload of 6 .. 10 ×107 instead of 2×107 for couplers 1..6 were reached and couplers 7 and 8 are mechanically limited by 70K cryogenic shield, reaching only 2.6×107; For the power coupler re-assembly with shifted Qload range module cavity and coupler vacua were vented with a dry nitrogen with a standard Eu-XFEL slow-venting procedure; Short pulse high RF power mode test and conditioning were done after power coupler re-assembly; CW RF measurements with IOT are running now up to 10 MV/m; Settings: RF-FB on, ANC used for 30 Hz vibration only, Bias piezo on; Vector Sum (VS) amplitude/phase stability tests are being done; 1 8.4×107 2 6.8×107 3 1.1×107 4 9.1×107 5 7.5×107 6 6.6×107 7 2.6×107 8 achieved Qload.max | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018

Pulsed Module Test Update XM-3 module test data for short pulse mode Module XM-3 cavities degradation occurred after power coupler re-assembly. Cavity 3 FE increased 100 times - breakdown limit did drop from 41 to 31 MV/m with operating gradient 18 MV/m. Cavity 4 FE increased as well. Cavities 1,5,6,7 are also somewhat degraded with lower breakdown limit, by 2..5 MV/m. Cavities 1,2,5,6,8 FE conditioning was successful, FE decreased. Cavities 3,4,7 FE did not decrease with the conditioning attempt. Cavity 3 makes now most of module FE caused X-rays; Module XM-3 is limited as before with cavity 1 at 23.7 MV/m. Operating gradient is limited by cavity 3. | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018

CW Module Test Operation XM-3 CW module test run after short pulse conditioning CW mode test after coupler re-assembly with Eacc = 8..10 MV/m yielded the gamma radiation of ~ 1 mGy/min without conditioning effect; Pulsed high power RF test and conditioning did succeed in decreasing FE level; CW run after SP test at 10 MV/m shows almost no X-rays. before SP conditioning after SP conditioning | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018

CW Module Test Operation XM-3 CW module test LLRF setup Settings: RF-FB on, ANC on, Bias piezo on, <Eacc> = 12 MV/m. | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018

CW Module Test Operation XM-3 CW module test data update CW test run at 12 MV/m (X-rays = 5×10-5 mGy/min); Low field Q0 degraded from 3×1010 to 2×1010. | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018

CW Module Test Operation XM-3 CW module test: coupler temperatures and Qload VS stability and heat load CW test run at Qload = 4×107 and 12 MV/m for 15 hours; Coupler cold 70K window temperature increased from 70 to 120 K  OK; Qload decreased due to thermal antennae elongation by ~5%  OK. time 30.01.2018 09:57:00 02.02.2018 10:10:00 cavity T [K] Qload [×107] 1 76.2 4.03 106.6 3.91 2 75.7 107.9 3.79 3 75.9 4.05 112.6 3.90 4 73.1 4.02 108.5 3.78 5 80.1 4.04 120.8 3.85 6 76.6 119.1 3.94 7 78.7 2.64 115.0 2.61 8 76.5 2.58 106.7 | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018

CW Module Test Operation XM-3 CW module test data update Vector Sum amplitude/phase stability test run at Qload = 4×107 and 12 MV/m: dA/A = 0.007%, dPh = 0.015º | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018

Conclusion XM-3 CW module test summary E-XFEL type accelerating module XM-3 with 7 Large-Grain and 1 Fine-Grain SRF 9-cell TESLA-type cavities is being tested on the module test stand CMTB at DESY. CW and long pulse tests are being done, as well as short pulse ones; High Q0 was achieved at low field < 10 MV/m: 3×1010 at 2.0 K and 4×1010 at 1.8 K, at 24 MV/m Q0 ≳ 2×1010 at 2K in SP operation mode was also measured. The highest gradient for LP mode was 20.1 MV/m with DF=43.2%. Reached Vector Sum (VS) amplitude stability ~ 10-4, phase stability ~10 mdeg; Module XM-3 power couplers were re-assembled for higher Qload in CW operation and higher maximum Qload of 6 .. 10 ×107 instead of 2×107 for couplers 1..6 were reached. For the power coupler re-assembly with shifted Qload range module cavity and coupler vacua were vented with a dry nitrogen with a standard Eu-XFEL slow-venting procedure; Module XM-3 cavities degradation occurred after power coupler re-assembly – cavity 3 suffered most with increased FE. Pulsed high power RF test and conditioning did succeed in decreasing FE level; CW test gamma radiation did drop down considerably, but low accelerating field Q0 degraded from 3×1010 to 2×1010; VS amplitude/phase stability tests are being currently performed with dA/A = 0.007%, dPh = 0.015º achieved at the moment in CW operation mode at Qload = 4×107 and 12 MV/m; | CW accelerating module test progress at DESY | Denis Kostin, Jacek Sekutowicz, 6.02.2018