Commissioning and first operation of the XFEL cryogenic

Commissioning and first operation of the XFEL cryogenic system T. Schnautz Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany

Commissioning and first operation of the XFEL cryogenic system Overview: n General information about XFEL project n Overview of XFEL cryogenic equipment n XFEL refrigerating plant o HERA refrigerating plant XFEL refrigerating plant o Commissioning of XFEL refrigerating plant o Performance results n Cold compressors o Operational experiences o Bypass operation o 2 K pressure stability o Cold compressor lifetime problems o Recovery after shutdown (e. g. bearing failure) n Summary Beijing, June, 2018 Tobias Schnautz 2

Commissioning and first operation of the XFEL cryogenic system European XFEL Project 3 XFEL: • • Length of accelerator: 1500 m Length of facility: 3400 m Accelerator modules : 96 Design electron energy: 17. 5 Ge. V Start of beam operation: January, 2017 Start of user runs: September, 2017 • SASE-Operation of all three undulators with variable bunch pattern Electron energy in October, 2017: 14. 9 Ge. V • Beam operation with 5000 bunches / sec with high intensity of X-ray laser • XFEL enables simultaneous provision of different experiments with various and high puls -rates Beijing, June, 2018 Tobias Schnautz XFEL cryogenic system: • • 671 control valves 2647 temperature sensors 800 pressure sensors 212 flow sensors >100 level sensors • > 220000 properties 433 regulation loops > 22000 records

Commissioning and first operation of the XFEL cryogenic system European XFEL Project 768 superconducting 9 -cell 1. 3 GHz cavities Helium II bath cooling at 2. 0 K - 5/8 K and 40/80 K thermal shields n. European XFEL Project 8 cavities + sc Quadrupole = 12 m Cryomodule Beijing, June, 2018 Tobias Schnautz 4

Commissioning and first operation of the XFEL cryogenic system Overview 5 Former HERA FLASH Beijing, June, 2018 Tobias Schnautz XFEL

Commissioning and first operation of the XFEL cryogenic system Overview 6 XFEL-Subplant 41 Contributions SC SC SC XFEL-Subplant 43 SC SC SC LINDE Beijing, June, 2018 Tobias Schnautz SC SC Coldbox 41 Coldbox 43

Commissioning and first operation of the XFEL cryogenic system Overview 7 XFEL-Subplant 41 SC Contributions SC SC XFEL-Subplant 43 SC SC SC LINDE SC SC Coldbox 41 Coldbox 43 n Re-arrangement of expansion turbines n. LN 2 heat exchanger removed 50% of piping modified Beijing, June, 2018 Tobias Schnautz To be modified To be removed No changes

Commissioning and first operation of the XFEL cryogenic system Overview 8 XFEL-Subplant 41 SC SC SC XFEL-Subplant 43 SC SC SC Contributions LINDE XFEL-Purifier Coldbox 41 Beijing, June, 2018 Tobias Schnautz Coldbox 43

Commissioning and first operation of the XFEL cryogenic system Overview 9 SC Contributions LINDE Distribution Box DB 54 SC SC SC XFEL-Purifier Coldbox 41 Beijing, June, 2018 Tobias Schnautz SC Coldbox 43

Commissioning and first operation of the XFEL cryogenic system Overview 10 AMTF Cryo Plant (Building 54) Warm He-Pumps XRTL Contributions LINDE DEMACO BINP Shaft Cold Compressors CB 44 Distribution Box XLVB Beijing, June, 2018 Tobias Schnautz Distribution Box DB 54 SC SC XFEL-Purifier Coldbox 41 Coldbox 43

Commissioning and first operation of the XFEL cryogenic system Overview 11 AMTF Cryo Plant (Building 54) Warm He-Pumps XRTL Contributions LINDE DEMACO BINP Injector EC 3, 9 GHz CM FC Beijing, June, 2018 Tobias Schnautz Distribution Box DB 54 SC SC XFEL-Purifier Shaft Cold Compressors CB 44 Distribution Box XLVB SC Coldbox 41 Linac Coldbox 43

Commissioning and first operation of the XFEL cryogenic system Overview 12 AMTF Cryo Plant (Building 54) Warm He-Pumps XRTL Contributions LINDE DEMACO BINP Injector SC SC SC XFEL-Purifier Shaft Cold Compressors CB 44 Distribution Box XLVB SC SC Distribution Box DB 54 Coldbox 41 Coldbox 43 Linac 1 2 3 FC CMS EC FC CMS SCB EC 3, 9 GHz CM FC FC CMS EC EC 3, 9 GHz CM FC FC: Feed cap EC: End cap CMS: Cryomodul string SCB: String connection box Beijing, June, 2018 Tobias Schnautz SC SCB CMS EC Main Linac

Commissioning and first operation of the XFEL cryogenic system XFEL cryo plant Cryo capacity 13 Croygenic plant-capacity: Performance requirements vs. performance results: Parallel coldbox operation: CB 41 CB 43 CB 41 + CB 43 + Cooling loop unit DESY calculated DESY specification Linde offer (calculated + safety margin) (guaranteed) (expected) Test results CB 41 + CB 43 2 K k. W 1. 46 1. 9 2. 01 > 1. 9 5 K – 8 K k. W 2. 4 3. 6 3. 95 4. 0 40 K – 80 K k. W 16. 0 24 24 26. 12 25. 9 Conclusion: n Guarantee values for parallel coldbox operation have been exceeded! Beijing, June, 2018 Tobias Schnautz

Commissioning and first operation of the XFEL cryogenic system XFEL cryo plant Cryo capacity 14 Croygenic plant-capacity: Performance requirements vs. performance results: CB 41 Single coldbox operation: CB 41 Cooling loop unit DESY calculated DESY specification Linde offer (calculated + safety margin) (guaranteed) (expected) Test results CB 41 2 K k. W 1. 46 1. 9 - 2. 01 > 1. 9 5 K – 8 K k. W 2. 4 3. 6 - 3. 03 2. 74 40 K – 80 K k. W 16. 0 24 - 20. 2 18. 14 Conclusion: n Single coldbox operation is sufficient for operation of XFEL Beijing, June, 2018 Tobias Schnautz

Commissioning and first operation of the XFEL cryogenic system First cooldown Linac 15 First cooldown: XFEL Linac Cooldown with one coldbox 300 K Start asymmetrical operation of two coldboxes to speed up cooldown Recovery of cold return flows in coldboxes to enhance cryogenic capacity Fast cooldown at temperatures below liquid nitrogen (no more thermal stress) 4 K 10. 12. 2016 Beijing, June, 2018 Tobias Schnautz 27. 12. 2016

Commissioning and first operation of the XFEL cryogenic system Cold compressors Operational challenges 16 Cold compressors: Operational challenges: n Small dynamic range for operation o Designed for one special working point o Deviations from this working point have to be compensated to avoid shutdown n Cold compressors are very sensitive towards massflow-, pressure- and temperature-changes in the 2 K-return flow o Massflow (-stability) is most important o Required massflow has to be “produced” XFEL Refrigerating plant Cold compressors CB 44 2 K return flow XFEL Linac & Injector Ideal operating field Beijing, June, 2018 Tobias Schnautz

Commissioning and first operation of the XFEL cryogenic system Cold compressors Operational challenges 17 Cold compressors: Operational challenges: n Small dynamic range for operation o Designed for one special working point o Deviations from this working point have to be compensated to avoid shutdown in n Choke operation: Should be avoided as cryo capacity decreases n Surge operation: Not possible. Crossing the surge line … • breakdown of operation • unnecessary loads on cold compressor motors • unnecessary downtime (5 -8 hours recovery time) Beijing, June, 2018 Tobias Schnautz el XFEL Linac & Injector rg 2 K return flow Su XFEL Refrigerating plant XFEL Cold compressors Refrigerating plant CB 44 e n Cold compressors are very sensitive towards massflow-, pressure- and temperature- changes in the 2 K-return flow o Massflow(-stability) is most important o Required massflow has to be “produced”

Commissioning and first operation of the XFEL cryogenic system Cold compressors Requirements on XFEL cold compressors 18 Requirements on XFEL cold compressors: n Massflow compensation avoid CC-shutdowns caused by heat load changes n Stand alone operation & re-connection of XFEL Linac/injector at sub atmospheric pressure Reduction of recovery time Cold compressor bypass system can fulfill these requirements XFEL Refrigerating plant Cold compressors CB 44 XFEL Linac & Injector CC-bypass n 2 K Pressure stability: < 2% n High availability (Exchange of cold compressor motors for maintenance after 16. 000 hrs) n Suction pressure: 24 mbar - 1000 mbar n 30% turn down capacity (by reducing the suction pressure of warm screw compressors) Beijing, June, 2018 Tobias Schnautz

Commissioning and first operation of the XFEL cryogenic system Cold compressors Bypass operation 19 Bypass operation: Massflow compensation, temperature adjustment & stand alone operation 2 K supply (~4. 5 K) 2 K supply (linac) Cold compressors (require ~110 g/s) Cold compressor bypass functions: 1. Mass flow compensation 2. Temperature adjustment 3. Stand alone operation Beijing, June, 2018 Tobias Schnautz

Commissioning and first operation of the XFEL cryogenic system Cold compressors Bypass operation 20 Bypass operation: Massflow compensation, temperature adjustment & stand alone operation 2 K return flow: 70 g/s 2 K supply (~4. 5 K) 2 K supply (linac) 2 K return (linac) Cold compressors (require ~110 g/s) Beijing, June, 2018 Tobias Schnautz

Commissioning and first operation of the XFEL cryogenic system Cold compressors Bypass operation 21 Bypass operation: Massflow compensation, temperature adjustment & stand alone operation 2 K return flow: 70 g/s 2 K supply (~4. 5 K) 2 K supply (linac) 2 K return (linac) Cold compressors (require ~110 g/s) 20 K return (coldbox) Beijing, June, 2018 Tobias Schnautz

Commissioning and first operation of the XFEL cryogenic system Cold compressors Bypass operation 22 Bypass operation: Massflow compensation, temperature adjustment & stand alone operation 2 K return flow: 70 g/s 2 K supply (~4. 5 K) 2 K supply (linac) 2 K return (linac) Cold compressors (require ~110 g/s) 20 K return (coldbox) CC-bypass has to produce: 40 g/s Beijing, June, 2018 Tobias Schnautz

Commissioning and first operation of the XFEL cryogenic system Cold compressors Operational experiences - bypass operation 23 Bypass operation: Massflow compensation, temperature adjustment & stand alone operation Real CC mass flow: 2 K return flow + CC-bypass flow 2 K return flow: 70 g/s 2 K supply (~4. 5 K) 2 K supply (linac) 2 K return (linac) Cold compressors (require ~110 g/s) 20 K return (coldbox) CC-bypass has to produce: 40 g/s CC inlet temperature is adjusted by use of two heat exchangers in CC-bypass Beijing, June, 2018 Tobias Schnautz

Commissioning and first operation of the XFEL cryogenic system Cold compressors Bypass operation 24 Bypass operation: Massflow compensation Required massflow 110 g/s Real massflow = (2 K return flow + bypass flow) Real massflow 110 g/s Required massflow Bypass flow 60 g/s Bypass flow 50 g/s 60 g/s Surge shutdown 2 K return flow 50 g/s 2 K return flow (linac & injector) 22. 02. 2017 (12: 00) Massflow bypass 25. 02. 2017 (10: 00) 20. 03. 2017 (06: 00) Conclusion: n CC-bypass operation delivers reasonable reactions on changes in 2 K return flow Beijing, June, 2018 Tobias Schnautz 20. 03. 2017 (12: 00)

Commissioning and first operation of the XFEL cryogenic system Cold compressors 2 K pressure stability 25 Cold compressors: 2 K Pressure stability n Specified pressure stability: < 2% (31 mbar +/- 0. 6 mbar) - could be demonstrated by Linde Improvement of 2 K pressure stability ü n Cascaded pressure regulation “CPR” (DESY) Pressure controller CC Cold compressors CB 44 Input Output Pressure controller linac ? ? 31 mbar – pressure drop Set pressure CC-inlet: dynamic Set pressure linac: 31 mbar 1. 5 km XFEL Linac & Injector o Event in linac reaches cold compressors with certain delay o Situation/condition in linac can differ from situation at inlet of CCs Pressure linac o Use of pressure controller linac: o Use of pressure controller CC: may not be satisfying! CC-surges can be created! 2 K Pressure stability in linac 31 mbar Set-pressure linac Pressure CC-inlet Both pressure controllers should be used for pressure adjustment in 2 K circuit (cascaded regulation)! Beijing, June, 2018 Tobias Schnautz 29 mbar Set-pressure CC-inlet

Commissioning and first operation of the XFEL cryogenic system Cold compressors Operational experiences – 2 K pressure stability 26 Cold compressors: 2 K Pressure stability n Specified pressure stability: 2% (31 mbar +/- 0. 6 mbar) could be demonstrated by LKT Improvement of 2 K pressure stability n Cascaded pressure regulation “CPR” (DESY) n Automatic heat load compensation “AHLC” (DESY): Changes in the 2 K return flow – caused by dynamic RF operation - are determined automatically and compensation takes place in the linac by automatic heating in the 2 K liquid helium. Required massflow for CCs Talk by J. Penning Real massflow (2 K return flow + bypass massflow) 30. 9 mbar 2 K pressure 30. 6 mbar Massflow bypass 1% - pressure stability 30. 3 mbar Sudden RFshutdown (10 Ge. V) 05. 04. 2017 (09: 00) Sudden RFshutdown (10 Ge. V) 05. 04. 2017 (16: 00) 05. 04. 2017 (09: 00) Conclusion: n Cold compressors deliver a 2 K pressure stability better than 2%. n “CPR” and “AHLC” improve the 2 K pressure stability significantly to 0. 3%! Beijing, June, 2018 Tobias Schnautz 2 K return flow from linac 05. 04. 2017 (16: 00)

Commissioning and first operation of the XFEL cryogenic system Cold compressors Motor failures Current problems/challenges with cold compressors: CC-motor failures n CC-motors are equipped with ceramic ball bearings o Motors show systematic bearing problems n Specification: lifetime of cold compressor motors of at least 16000 hrs. o Due to the bearing failures, the specified lifetime could not yet be demonstrated o 2018: Two XFEL user-runs had to be interrupted caused by bearing damages o 900 h < lifetime of bearings < 9000 h n Root cause analysis by Linde Kryotechnik o Problem solving related to lifetime of CC-motors is ongoing o Definition of a design-upgrade is in progress Conclusion: n Downtime, caused by cold compressor issues, has to be reduced significantly o Duration of interruption in case of motor failure: at least 30 hours (for cryo group) n New CC-motor design has to be developed soon to … match the specified lifetime o … guarantee reliable XFEL user operation Beijing, June, 2018 Tobias Schnautz 27

Commissioning and first operation of the XFEL cryogenic system Cold compressors Recovery after shutdown (e. g. bearing failure) 28 Normal operation configuration Warm He pumps AMTF Distribution box XLVB XFEL Coldbox 1000 mbar Cold compressors CB 44 CC-bypass Beijing, June, 2018 Tobias Schnautz 29 mbar XFEL Linac & Injector 2 K return flow

Commissioning and first operation of the XFEL cryogenic system Cold compressors Recovery after shutdown (e. g. bearing failure) 1000 mbar Warm He pumps AMTF Operation configuration after surge – beam operation not possible, but linac can be kept cold at 31 mbar 29 mbar Distribution box XLVB XFEL Coldbox 1000 mbar Cold compressors CB 44 CC-bypass Beijing, June, 2018 Tobias Schnautz 29 1000 mbar XFEL Linac & Injector 2 K return flow Sudden shutdown (e. g. bearing failure)

Commissioning and first operation of the XFEL cryogenic system Cold compressors Recovery after shutdown (e. g. bearing failure) 1000 mbar Warm He pumps AMTF Operation configuration after surge – beam operation not possible, but linac can be kept cold at 31 mbar 29 mbar Distribution box XLVB XFEL Coldbox 1000 mbar Cold compressors CB 44 CC-bypass Beijing, June, 2018 Tobias Schnautz 30 XFEL Linac & Injector 2 K return flow 1. 2. 3. 4. 5. 6. Warm up Exchange of CC-motor Pump & purge Stand alone operation Cool down Internal pump down (< 29 mbar)

Commissioning and first operation of the XFEL cryogenic system Cold compressors Recovery after shutdown (e. g. bearing failure) 1000 mbar Warm He pumps AMTF Normal operation configuration after internal pumpdown and reconnection of XFEL linac/injector 29 mbar 1000 mbar CC-bypass Beijing, June, 2018 Tobias Schnautz XFEL Linac & Injector Distribution box XLVB XFEL Coldbox Cold compressors CB 44 31 < 29 mbar 2 K return flow Re-connection of linac at sub atmospheric pressure

Commissioning and first operation of the XFEL cryogenic system Cold compressors Recovery after shutdown (e. g. bearing failure) 32 Permanently adapt parameter to current situation Sequence for recovery after shutdown (e. g. bearing failure) 1. Switch XFEL linac from cold compressors to warm He pumps 2. Warm up of cold compressors 3. Exchange of CC-motor 4. Pump & purge 5. Stand alone operation 6. Cool down of cold compressors 7. Prepare for pump down 8. Strat internal pump down (< 29 mbar) 9. Start connection of cold compressors to XFEL Linac I. Open cold compressor inlet valves II. Re-connect XFEL linac at sub atmospheric pressure III. Prepare for process stabilization IV. Create sufficient return flow from linac (e. g. by heating) 10. Start cascaded regulation for pressure adjustment 11. Start heat load compensation 12. Stabilize operation Beijing, June, 2018 Tobias Schnautz Procedure has been automated by DESY for 99% to save time and personal!

Commissioning and first operation of the XFEL cryogenic system Summary XFEL cryogenic system: Summary n The commissioning of the XFEL cryo plant (4 K) was successful o The performance results comply with the specification n The first cooldown of the XFEL linac/injector was successful o No major problems occurred (e. g. cold leaks) n The 2 K pressure stability is excellent (0. 3%) o The cascaded pressure regulation in combination with the automatic heat load compensation improved the pressure stability significantly o Even dynamic procedures (power ramping, rf-shutdown, etc. ) can be compensated quite well without affecting the pressure stability drastically n The bearing problems of the cold compressor motors are not yet solved o Many theories were discussed, some of them were identified as relevant o Improvements since commissiong – but general problem still has to be solved o A new motor design has to be developed soon to guarantee reliable XFEL user operation n The recovery effort after a cold compressor shutdown (e. g. bearing failure) is minimized by … o … the possibility of the stand alone CC-bypass operation and o … the automation of the recovery procedure Beijing, June, 2018 Tobias Schnautz 33

Commissioning and first operation of the XFEL cryogenic system Cold compressors Thank you for your attention Beijing, June, 2018 Tobias Schnautz 34