1. 1 st stage Possible extension XFEL Cryo System Project X Collaboration Meeting, FNAL September 8-9, 2010 Bernd Petersen DESY MKS (XFEL WP10 & WP13)

2. 2 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Outline XFEL accelerator structure ‘TESLA’ technology Basic cryogenic parameters Tasks & up-grade scenarios Heat load capacities of XFEL refrigerator Use of former HERA refrigerators Lay out of XFEL cryogenic system Cold turbo compressor issues Pressure variations/stability CW operation of TESLA cavities (reference to BESSY)

3. 3 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS XFEL Photon Parameters

4. 4 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS XFEL Accelerator requirements: 14 – 20 GeV electron beam energy About 642 -962 superconducting RF cavities at 23 MV/m -> TESLA –technology pulsed 10 Hz operation two independent injectors (1.3 GHz cm + 3.9 GHz cm each) Main linac: 1.65 km 80 -120 cryomodules Booster 12 cryomodules two bunch-compressor sections -> transferline bypasses needed 0.1 nm Photons X-ray FEL

5. 5 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS XFEL-Accelerator Tunnel XTL

6. 6 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS 10 Hz pulsed operation each cryomodule consist of: 8 1.3 GHz 9-cell Nb cavities (2K) 1 magnet package (2K) 2 thermal shields (5-8K;40-80K) 8 main RF couplers 8 cold tuners Main features of XFEL-cryomodule design based on the TESLA/TTF –type III design -> use of ‚TESLA‘-technology Cryomodule cross-section XFEL requirement: 23.6 MV/m

7. 7 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Accelerator Module (Cryomodule) The XFEL accelerator module is based on the 3 rd cryomodule generation tested at the TESLA Test Facility and designed by INFN. Already 12 cryomodules have been built and commissioned for the TTF Linac. Length 12.2 m Total weight 7.8 t 38” carbon steel vessel 300 mm He gas return pipe acting as support structure 8 accelerating cavities cavity to cavity spacing exactly one RF wavelength inter-module cavity to cavity spacing a multiple of one RF wavelength one beam position monitor / magnet unit manually operated valves to terminate the beam tube at both ends longitudinal cavity position independent from the contraction / elongation of the HeGRP during cool-down / warm-up procedure 16

8. 8 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS 2.2 K forward 40 K forward 2 K 2-phase cavity 2 K return 80 K return 8 K return RF main coupler magnet current feedthrough 5 K forward 4 K shield 70 K shield Accelerator Module (Cryomodule) 17

9. 9 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Safety Measures Safety flaps (up to DN300) installed on the vacuum vessel of each cryomodule LHC event : we reviewed helium release in XFEL tunnel

10. 10 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS XFEL Magnet Package and Cold BPM At the downstream end of the cavity string of each module a magnet package and an attached BPM is placed. a super-ferric quadrupole a vertical and a horizontal dipole BPM is either re-entrant (SACLAY design) or pick-up (DESY design) type. Quadrupole to BPM alignment is 0.3 mm and 3 mrad. The magnet design is done in collaboration with CIEMAT. The current leads are based on the CERN design used at LHC. 19 magnet package current leads beam position monitor 2 K two-phase line SC Magnet Package at 2K

11. 11 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Choice of cryogenic parameters 2K Helium II – bath: well below lambda transition close to heat conductivity maximum of saturated liquid Qo>10**10 for TESLA cavities (lower temperature has only limited advantage for pulsed RF operation) Low vapor pressure enables relative pressure stability in the order of less than +/- 1 % (problems with CCs !?) 5-8K circuit: 5K traditional from TESLA TDR (TESLA quad cooling,still main coupler thermal intercepts), fits to HERA cryo plant 40-80K circuit: Standard layout, fits to HERA plant

12. 12 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS TESLA Cavities show BCS temperature dependence in Cryomodule

13. 13 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS XFEL-Linac-Cryogenic tasks (TDR) - 944 sc Nb 1.3 ‑ GHz 9 ‑ cell cavities have to be cooled in a Helium II bath at 2K, Qo= 10**10, 23.6 MV/m, 10 Hz - 40 3.9 GHz cavities (in 2 cryomodules) - 104 1,3 GHz cryomodules in RF operation - 12 cryomodules in ‘cold stand-by’ - 2 ‚Cryo-Bypass-Transfer-Lines‘ (BCBTL) - at warm Bunch-Compressor sections - 2 independent injectors ( 1.3 GHz + 3.9 GHz cm each) 816 92 8 (NEW start ) 642 76 4 Very new start version

14. 14 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS XFEL project realization in stages Start version: 80 cryomodules 14 GeV Could be up-graded already during construction to 100 cryomodules 17.5 Gev Final up-grade (according to TDR): 120 cryomodules 20 Gev + cw injector

15. 15 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Heat loads & mass flows of final 20 GeV stage Subjects of process optimization 13.4 KW 4.5K eq

16. 16 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Heat loads & mass flows of 17.5 GeV stage 10.8 KW eq 4.5K

17. 17 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Continous operation of the refrigerator 24 h per day / 7 days per week Operation periods of 2 – 3 years without scheduled break of cold helium supply Avialability > 99% (without ‘utilities’ and process control) Operating conditions of XFEL Linac-Cryogenic

18. 18 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Use of HERA cryogenic plant Preliminary studies from TU Dresden and a detailed industrial study by LINDE KRYOTECHNIK AG -> 2 HERA refrigerators (8 KW eq 4.5K each) could be modified to XFEL- refrigerator ( + 2K system) Advantages: Only ½ of investment costs compared to new refrigerator No extra civil engineering effort Utilities exist Dis-advantages: Lower efficiency compared to new plant Re-use of worn equipment Parallel operation of 2 cold boxes challenging (symmetrical operation) There is still hope that only one CB will be sufficient to operate the 14 GeV linac ( or even the 17.5 GeV linac, if we’ll not need all the capacity of the overhead)

19. 19 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Concept of XFEL-cryogenic Distribution Box VALVE BOX 2K BOX CC F BCBTL MAIN LINAC INJECTORS BCBTL BOOSTER 3.9 GHz CMS CM F SCB VC Valve BOX CB AMTF SC

20. 20 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Main Transfer Line Piping Bridge to XSE

21. 21 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Cryogenic installations in XSE Distribution Box

22. 22 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Concept of XFEL-Linac Cryogenic 2 K return 40/80 K forward 40/80 K return, shield cooling 2.2 K forward lead cooling 5 K forward 8 K return, shield cooling 2 K return Injector 1 40/80 K forward 40/80 K return, shield cooling 2.2 K forward 5 K forward 8 K return, shield cooling module string 2 module string 1 warm gas collection pipe Up-graded HERA plant module string 9-10 cryogenic unit (9-10 strings), 1.7 km JTHEX Simplified flow scheme 40K -> 80K shield circuit (in series) 5K -> 8K shield circuit (in series) 2K circuit (supply in parallel,return in series) Injector 2 (not shown) DB-box simplified moved to XSE

23. 23 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Linac cryogenic ‚string‘ Cryogenic units of 12 cryomodules = ‚strings‘ String Connection Boxes contain all cryogenic instrumentation Breaking news: All individual cavity helium vessels will get a thermometer !

24. 24 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS 1660156197854044235420814166 Beam direction Laser-straight XFEL-linac BC Liquid Helium II supply Length [m] Deviation from gravity equipotential [mm] String 1String 11String 10String 9 72,761,552,334,726,017,70,0426,336,3 5 String 4 JT 8 Modules Gravity equipotential surface Disadvantage: 2-phase flow affected by gravitational forces One ‚String‘ = 12 cryomodules each of 12 m length

25. 25 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Bunch Compressor Bypass Transferline (only 1-phase helium) Feed-Box JT Cool-down/warm-up End-BOX ‚regular‘ string connection box Linac cryogenic components

26. 26 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Spec of Cold Turbo Compressors (CCs) DESY MKS has NO experience with the operation of CCs We need advice from CERN,J-Lab, SNS Up to now, we learned from our CERN/LHC colleagues: - ‘mixed-cycle’ approach mandatory - to increase CCs dynamic range - to restart from sub-atmospheric conditions of the linac - 5 stages approach too risky - make up of T,P, mass flow is a touchy operation

27. 27 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS CCs mixed-cycle approach DESY ‘mixed-cycle’ approach: we could use the JT-screw (minimum 650 mbar) and/or make use of our helium pump units of the Accelerator Module Test Facility (AMTF) 2 X 20 g/s at 20 mbar (sufficient for static loads) 100 g/s at 200 mbar for mixed cycle + Extra heat exchanger in distribution box

28. 28 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS 2K reference specification ( simplified) Cold Compressors T bath = f ( P bath ) 4.5 K load 40/80 K load HEX JT subcooler HEX VC SC Existing Refrigerator ‚mixed cycle‘ Critical for HERA CBs Details are subject of call for tender ! ?

29. 29 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Sources of pressure variations: heavy single cavity quench in FLASH Pressure [mbar] Mass flow [g/s] Temp [K] P at linac endcap P at helium pumps He mass flow T cavity He vessel 5 min !!!

30. 30 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS XFEL pressure stability Spec RF change of TESLA cavities vs pressure change : about 50 Hz / mbar Note from DESY RF experts: fluctuations not larger than +/- 35 Hz to avoid RF phase shifts -> pressure stability better than +/- 0.7 mbar required We specify 1% relative pressure stability -> 31 mbar +/- 0.3 mbar (LHC 5 % relative pressure changes caused by the accelerator components) Our question in call for tender: How does the CCs regulation react on a sudden mass flow change of 10% ?

31. 31 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Pressure variations expected in XFEL linac Arkadiy‘s questions: 1. Range of presures during normal operations ? -> 31 mbar +/- 0.3 mbar ( 1%) 2. Timescale ? -> Hours ! From FLASH experience we expect very stable conditions 3. Occasional/rare pressure variations ? -> Switching on/off RF, Quenches (see FLASH example) For the switching of RF we‘ll need some ‚ramping‘ by means of electrical heaters Trips of CCs ?

32. 32 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS CW-operation of TESLA cavities -> BESSY(1) W.Anders, J.Knobloch et al. at DESY: see SRF2009 paper D.Kostin, WD Möller et al.

33. 33 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS CW-operation of TESLA cavities -> BESSY(2)

34. 34 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS CW-operation of TESLA cavities -> BESSY(3)

35. 35 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS CW-operation of TESLA cavities -> BESSY(4)

36. 36 Project X collaboration meeting, FNAL, September 8-9, 2010 Bernd Petersen DESY MKS Summary XFEL accelerator structure ‘TESLA’ technology Basic cryogenic parameters Tasks & up-grade scenarios Heat load capacities of XFEL refrigerator Use of former HERA refrigerators Lay out of XFEL cryogenic system Cold turbo compressor issues Pressure variations/stability CW operation of TESLA cavities (reference to BESSY)