1. Current Leads for Project X Tom Peterson and Tom Nicol With input from Sergey Cheban, Iouri Terechkine, Arkadiy Klebaner, Yuriy Orlov Page 1Current Leads for Project X, 14 May 2013

2. CW Linac Cryomodules Current Leads for Project X, 14 May 2013Page 2

3. SSR Cryomodule Cooling Scheme Page 3Current Leads for Project X, 14 May 2013

4. 4 From John Pfotenhauer, University of Wisconsin, Madison

5. CERN Lead Assembly Current Leads for Project X, 14 May 2013 5

6. Conductive Lead Choice CERN developed conductively cooled leads for low current (up to ~ 200 A) corrector magnets DESY is adapting them for 2 Kelvin magnets in XFEL Early in the Project X conceptual design work, we opted for conductively cooled leads I’ll explain why after a quick look at current leads Current Leads for Project X, 14 May 20136

7. Conductively Cooled Leads Current Leads for Project X, 14 May 2013Page 7

8. Lead Assembly Current Leads for Project X, 14 May 2013 8

9. SSR1 Lead Assembly Current Leads for Project X, 14 May 2013 9

10. SSR1 Cryomodule Current Leads for Project X, 14 May 2013 10

11. SSR1 Cryomodule Current Leads for Project X, 14 May 2013 11

12. Thermal Shield Connection Current Leads for Project X, 14 May 2013 12

13. Lead Assembly for Analysis Current Leads for Project X, 14 May 2013 13 300 K 2 K 80 K 5 K

14. Thermal intercepts The primary design challenge for the conductively cooled leads is the design of the thermal intercepts We want electrical isolation, but not thermal isolation From Tom N.: “One of the issues that has plagued leads at DESY and CERN is intercepting heat along the leads. Those designs rely on clamped connections to the lead conduit. We plan to braze the lead tubes to the intercept blocks prior to inserting the leads and potting. Sasha Makarov has been working with us on the details of insulating and potting after forming of the leads.” Current Leads for Project X, 14 May 201314

15. Conductively Cooled Lead Current Leads for Project X, 14 May 2013 15 Case 1: 10 Ga, RRR 100 copper Case 2: 12 Ga, RRR 100 copper

16. Current Leads for Project X, 14 May 201316 Vapor-cooled Current Leads Well-developed technology Much information in the cryogenics literature HTS materials work very well in current leads up to 80 K

17. American Magnetics, Inc. (AMI) current lead design by K. R. Efferson (ref 2) Current Leads for Project X, 14 May 201317

18. Current Lead Heat Impact Current Leads for Project X, 14 May 201318

19. Comparing Vapor Cooling Current Leads for Project X, 14 May 201319

20. Our choice of conductively cooled leads for SSR Small overall impact on cryo capacity required. Although conductively cooled current leads account for about a third of the 5 K heat load, the overwhelming dominance of the 2 K heat load in the total swamps out the effect on overall cooling power requirements. Simplicity of operation -- no vapor cooling Flexibility of integration into the cryostats -- conductively cooled leads are essentially conduit which may be routed as required Cryogenic system advantages (next slides) Comment: I believe the expense of the conductively cooled leads is still an artifact of some design and integration issues which will be resolved with further engineering work and experience. We should also follow closely the development of the conductively cooled current leads for XFEL at DESY. Current Leads for Project X, 14 May 201320

21. NML Cryoplant Current Leads for Project X, 14 May 201321

22. Why 5 K to 8 K? 4.5 K magnets have the disadvantage of requiring a 4.5 K liquid/vapor system. One needs to utilize the 4.5 K latent heat of vaporization either in a subcooler/recooler or directly in bath cooling the magnets. Thus, one needs another liquid level control system and 4.5 K vapor return. In long string of cryomodules in Project X, we prefer to avoid 2-phase 4.5 K flow and vapor return for the nominally 5 K thermal shield 5 K to 8 K at ~3 bar pressure allows single phase flow with large heat capacity (absorbs about 35 J/g) –Lower flow rate –Smaller pipes are OK due to the reduced flow rate, higher pressure and density, and higher allowable pressure drop –Placing the magnets at 2 K frees up the temperature constraint on the nominally 5 K flow This was a step in the evolution of the TESLA cryomodule and is the concept for the nominally 5 K circuit for XFEL Current Leads for Project X, 14 May 201322

23. From Tom Nicol We have a nice plan for incorporating instrumentation into the conduction cooled lead design by adding one or two parallel lead tubes for voltage taps, etc. I talked to Ed Bonnema at Meyer about the high cost of the ILC leads and he was very vocal about the cost being driven by the complex plating and machining of the conductor to meet the CERN criteria. We don't rely on any of that, opting rather for a uniform commercially available conductor. Current Leads for Project X, 14 May 201323

24. Summary In my opinion, conductively cooled leads provide operational simplicity with little additional cost relative to vapor cooling Page 24Current Leads for Project X, 14 May 2013

25. Current lead references 1. J.M. Lock, “Optimization of Current Leads into a Cryostat,” Cryogenics, Dec 1969. 2. K.R. Efferson, “Helium Vapor Cooled Current Leads,” The Review of Scientific Instruments, Vol 38, No. 12, Dec 1967. 3. D. Guesewell and E. –U. Haebel, “Current Leads for Refrigerator-Cooled Large Superconducting Magnets,” 3rd International Conference on High-energy Physics and Nuclear Structure, New York, NY, USA, 8 - 12 Sep 1969. 4. J.A. Demko, et al, “Thermal Optimization of the Helium Cooled Power Leads for the SSC,” Proceedings of the Supercollider 4 Conference, New Orleans, 1992. 5. G. Citver, S. Feher, T.J. Peterson, C.D. Sylvester, “ Thermal Tests of 6 kA HTS Current Leads for the Tevatron,” Advances in Cryogenic Engineering, Vol. 45B, pg. 1549. Current Leads for Project X, 14 May 2013 25

26. Current lead references 5. J. Brandt, S. Feher, T.J. Peterson, W.M. Soyars, “HTS Leads in the Tevatron,” Advances in Cryogenic Engineering, Vol. 47A, pg. 567. 6. A. Ballarino, S. Mathot, and D. Milani, “13000 A HTS Current Leads for the LHC Accelerator: from Conceptual Design to Prototype Validation,” LHC Project Report 696, Presented at the 6th European Conference on Applied Superconductivity (EUCAS 2003) 14-18 September 2003. 7. T.P. Andersen, V. Benda, B. Vullierme, “600 A Current Leads with Dry and Compact Warm Terminals,” LHC Project Report 605 8. A. Ballarino, “Conduction-Cooled 60 A Resistive Current Leads for LHC Dipole Correctors,” LHC Project Report 691 Current Leads for Project X, 14 May 2013 26

27. Reference Slides Current Leads for Project X, 14 May 201327

28. Current lead design issues, thermal and fluid dynamic Heat transfer for convective cooling –Huge range of fluid temperatures up the lead, hence large changes in fluid density, velocity, convection coefficients Cooling conditions – saturated vapor –Many papers and designs consider current leads for operation in a dewar –“Self-cooling” in generating saturated vapor from boiling liquid based on heat transfer to bottom of lead –Very low pressure drop up the lead is required Cooling conditions – pressurized helium (subcooled, supercritical, or gas at the lead base) –Flow control is independent of heat input –Heat may be convected into the flow stream passing the lead Current Leads for Project X, 14 May 2013 28

29. Average system-wide current lead flows for the Tevatron at 4 kA (data taken by Tom P., 6 May 1987) Current Leads for Project X, 14 May 201329 Notes: feedcan and power spool had very different configurations, with better convective cooling at the lead base in the feedcan. Average is about 0.4 grams/sec for 4 kA. 0.1 grams/sec helium cooling per kA was typical also at MTF.

30. Typical temperature distribution for vapor-cooled leads Current Leads for Project X, 14 May 201330 SSC study (ref 4)

31. 650 MHz CM for reference No magnets in the high-beta version Perhaps a 3C-FD-3C configuration in the beta = 0.6, 650 MHz cryomodule, no design yet The following slides show the 650 MHz, beta =0.9 cryomodule concept for reference Current Leads for Project X, 14 May 201331

32. 650 MHz Cryomodule Beam pipe (100mm-ID) Heat Exchanger Cryogenic stuff: bayonets connections (He supply and return), Cryogenic valve control system Power couplers Ports for access Tuner motors Support posts (1-fix, 2-sld) Vacuum Vessel (pipe: 48”-OD,.375”-wall) Page 32Current Leads for Project X, 14 May 2013

33. 650MHz Cryomodule Layout (Desy Style, stand alone) Overall length-12250mm Interconnection bellows length-135.5mm Beam pipe ID-100mm 1 gate valve for each end of Beam Pipe Number of Support posts-3 (1-Fix, 2-Sliding) 300mm pipe (concept) serves as strong back, as the 2-phase helium pipe, also providing a large vapor buffer volume. Number of Cavitis-8 Couplers distance -1468.9mm Heat exchanger Insulation Vacuum Relief valve Page 33Current Leads for Project X, 14 May 2013

34. 650MHz Cryomodule. Cold Mass -80K shield with Al extrusions not shown -5K piping with thermal intercepts -300mm pipe with support bearing system for Cavity string -invar rod (keeps the Z distance between cavities) -thermal shrinkage compensator (Bellows) -cavity string with Gate valves (?) Page 34Current Leads for Project X, 14 May 2013

35. 650 MHz Cavity with Blade Tuner -Ti-Vessel -He connection compensator -Blade tuner (End Tuner?) -Flange connection (Ti-St.Steel transition?) Page 35Current Leads for Project X, 14 May 2013