1. The HiLumi LHC Design Study (a sub-system of HL-LHC) is co-funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404. Crab Cavity Cryostat Fabrication and Challenges Tom Peterson (FNAL) FNAL-LHC Crab Cavity Engineering Meeting 14 Dec 2012

2. LHC Crab Cavity Cryostat, 14 Dec 2012 Crab cavity cryostat discussion Fabrication of the different types of cryostat and their advantage and disadvantages should be reviewed. Fabrication of the different types of cryostat and their advantage and disadvantages should be reviewed. Challenges in the design choice, fabrication steps, integration along with feasibility of a two cavity cryostat within the specified scheduled should be reviewed and mitigation should be discussed. Challenges in the design choice, fabrication steps, integration along with feasibility of a two cavity cryostat within the specified scheduled should be reviewed and mitigation should be discussed. 2

3. LHC Crab Cavity Cryostat, 14 Dec 2012 Final crab cavity system requirements Definition of requirements is still in progress Definition of requirements is still in progress Elements of these requirements include: Elements of these requirements include: Interfaces to the LHC accelerator system, cryogenic system, and tunnel infrastructure Interfaces to the LHC accelerator system, cryogenic system, and tunnel infrastructure Thermal conditions, cavity temperature, intercept temperatures, heat loads Thermal conditions, cavity temperature, intercept temperatures, heat loads Cavity arrangement, supporting structure and possibility for alignment, beam-beam spacing and allowance for two beams, how many cavities per cryostat? 2 Cavity arrangement, supporting structure and possibility for alignment, beam-beam spacing and allowance for two beams, how many cavities per cryostat? 2 Constraints from vertical and horizontal crabbing schemes RF coupler and HOM/LOM configurations and constraints Constraints from vertical and horizontal crabbing schemes RF coupler and HOM/LOM configurations and constraints Tuner configurations and constraints Tuner configurations and constraints Instrumentation requirements Instrumentation requirements Cryostat, piping, and helium vessel safety, code compliance requirements from final design. Cryostat, piping, and helium vessel safety, code compliance requirements from final design. 3

4. LHC Crab Cavity Cryostat, 14 Dec 2012 Given the final system requirements above, how may the prototype differ from the final design? Cavity support structure, same as final design? YES Cavity support structure, same as final design? YES Arrangement of multiple cavities. Same total number of cavities? NO Arrangement of multiple cavities. Same total number of cavities? NO Provisions in the prototype for one beam only? PERHAPS Provisions in the prototype for one beam only? PERHAPS Cryostat vacuum vessel differences SIGNIFICANT Cryostat vacuum vessel differences SIGNIFICANT RF couplers and HOM/LOM configuration and orientation through the cryostat SIMILAR to final design RF couplers and HOM/LOM configuration and orientation through the cryostat SIMILAR to final design Special instrumentation not in the final cryostat Cryogenic connections, interfaces to infrastructure may differ YES, but not yet defined Special instrumentation not in the final cryostat Cryogenic connections, interfaces to infrastructure may differ YES, but not yet defined 4

5. LHC Crab Cavity Cryostat, 14 Dec 2012 Peak warm pressure Compressor suction set pressure –1.2 bar (to avoid subatmospheric excursions) Control margin –+/- 0.2 bar Relief set pressure margin –+ 0.3 bar above control excursions (a judgment here, would like 0.5 bar) Suction relief set pressure –1.7 bar (from 1.2 + 0.2 + 0.3 bar above) Pressure drop from far helium vessel to relief –+ 0.1 bar (needs to be determined for specific system, but probably low for the low flow in the warm situations) Peak warm pressure –1.8 bar (note that 0.5 bar set pressure margin, which would be better ==> 2.0 bar peak warm pressure) Conclusion: 2.0 bar warm MAWP is a practical lower limit ILC presentation – Tom Peterson 5

6. LHC Crab Cavity Cryostat, 14 Dec 2012 Cold peak pressures - 1 Loss of vacuum to air –“Safety Aspects for the LHe Cryostats and LHe Containers,” by W. Lehman and G. Zahn, ICEC7, London, 1978 “3.8 W/sq.cm. for an uninsulated tank of a bath cryostat” “0.6 W/sq.cm. for the superinsulated tank of a bath cryostat” –“Loss of cavity vacuum experiment at CEBAF,” by M. Wiseman, et. al., 1993 CEC, Advances Vol. 39A, pg 997. Maximum sustained heat flux of 2.0 W/sq.cm. –LEP tests and others have given comparable (2.0 to 3.8 W/sq.cm.) or lower heat fluxes –Film boiling of helium with 60 K surface is about 2.5 W/sq.cm. ILC presentation – Tom Peterson 6

7. LHC Crab Cavity Cryostat, 14 Dec 2012 Cold peak pressures - 2 Input parameters –Heat flux as limited by Rate of air inleak Surface heat transfer –Total surface area involved Can be limited by vacuum breaks, fast valves –Initial conditions Note that 4.5 K just after filling (as opposed to 2 K when the large, low pressure volume acts as a buffer) is the worst case! –Pipe diameters out to the helium vent –Overall distances and pipe lengths out to the helium vent A finer degree of segmentation can reduce pipe diameter requirements ILC presentation – Tom Peterson 7

8. LHC Crab Cavity Cryostat, 14 Dec 2012 Cold peak pressures - 3 Relief pressure will be suction relief set pressure (for example, 1.7 bar) Heat flux of 10’s of KW to liquid helium Mass flows of many kg/sec Pressure drops to vent may result in peak pressures of 2.5 bar to 4 bar locally Maintaining a low peak pressure (e.g., 2.5 bar) requires larger piping and/or shorter vent path lengths ILC presentation – Tom Peterson 8

9. LHC Crab Cavity Cryostat, 14 Dec 2012 Conclusion for MAWP “Maximum Allowable Working Pressure” (MAWP) –The pressure which we declare on our engineering notes will be the maximum the vessel will see –Relief valves and vent piping are sized to prevent pressure exceeding this value 2 bar differential pressure warm (minimum!) –Helium space to cavity vacuum –Helium space to insulating vacuum 2.5 bar to 4 bar differential pressure cold –Helium space to cavity vacuum –Helium space to insulating vacuum –Higher (closer to 4 bar) is better in allowing smaller diameter and longer pipes to vent valves ILC presentation – Tom Peterson 9

10. LHC Crab Cavity Cryostat, 14 Dec 2012 Safety/compliance issue In the U.S., Europe, and Japan, these helium containers and part or all of the RF cavity fall under the scope of the local and national pressure vessel rules. Thus, while used for its superconducting properties, niobium ends up also being treated as a material for pressure vessels. For various reasons, it is not possible to completely follow all the rules of the pressure vessel codes for most of these SRF helium vessel designs Presentation to DOE, 21 Sep 2011 10

11. LHC Crab Cavity Cryostat, 14 Dec 2012 Issues for code compliance Cavity design that satisfies level of safety equivalent to that of a consensus pressure vessel code is affected by »use of the non-code material (niobium), »complex forming and joining processes, »a shape that is determined entirely by cavity RF performance, »a thickness driven by the cost and availability of niobium sheet, »and a possibly complex series of chemical and thermal treatments. Difficulties emerge pressure vessel code compliance in various areas »Material not approved by the pressure vessel code »Loadings other than pressure Thermal contraction Tuning »Geometries not covered by rules »Weld configurations difficult to inspect Presentation to DOE, 21 Sep 2011 11

12. LHC Crab Cavity Cryostat, 14 Dec 2012 General solution In applying ASME code procedures, key elements demonstrating the required level of design safety are »the establishment of a maximum allowable stress »And for external pressure design, an accurate approximation to the true stress strain curve Apply the ASME Boiler and Pressure Vessel Code as completely as practical »Exceptions to the code may remain »We have to show the risk is minimal Satisfy the requirement for a level of safety greater than or equal to that afforded by ASME code. Fermilab, Brookhaven, Jefferson Lab, Argonne Lab, and others in the U.S. have taken a similar approach Presentation to DOE, 21 Sep 2011 12

13. LHC Crab Cavity Cryostat, 14 Dec 2012 Conclusions Niobium, niobium-titanium, electron beam welding, and other features required for the proper function of superconducting RF cavities create problems with respect to pressure vessel codes in all regions of the world With significant effort, laboratories have found various ways to provide levels of safety equivalent to the applicable code rules These methods involve taking some very conservatively low values for niobium yield strength due to heat treatments and uncertainty, and doing analysis and quality assurance inspections in accordance with code rules as much as possible Treating the vacuum vessel as the primary containment volume or excluding the niobium material from the pressure boundary definition may be feasible in some cases Presentation to DOE, 21 Sep 2011 13

14. LHC Crab Cavity Cryostat, 14 Dec 2012 Cryomodule requirements -- major components Dressed RF cavities Dressed RF cavities RF power input couplers RF power input couplers One intermediate temperature thermal shield One intermediate temperature thermal shield Cryogenic valves Cryogenic valves 2.0 K liquid level control valve 2.0 K liquid level control valve Cool-down/warm-up valve Cool-down/warm-up valve 5 K thermal intercept flow control valve 5 K thermal intercept flow control valve Pipe and cavity support structure Pipe and cavity support structure Instrumentation -- RF, pressure, temperature, etc. Instrumentation -- RF, pressure, temperature, etc. Heat exchanger for 4.5 K to 2.2 K precooling of the liquid supply flow Heat exchanger for 4.5 K to 2.2 K precooling of the liquid supply flow 14

15. LHC Crab Cavity Cryostat, 14 Dec 2012 Cryomodule requirements -- major interfaces Bayonet (or other style) connections for helium supply and return Bayonet (or other style) connections for helium supply and return Vacuum vessel support structure Vacuum vessel support structure Beam tube connections at the cryomodule ends Beam tube connections at the cryomodule ends Double vacuum valves Double vacuum valves Guard vacuum pumping Guard vacuum pumping Thermal intercepts Thermal intercepts Allowance for thermal contraction Allowance for thermal contraction RF waveguide to input couplers RF waveguide to input couplers Instrumentation connectors on the vacuum shell Instrumentation connectors on the vacuum shell Alignment fiducials on the vacuum shell with reference to cavity positions. Alignment fiducials on the vacuum shell with reference to cavity positions. Vacuum system for pumping insulating vacuum Vacuum system for pumping insulating vacuum 15

16. LHC Crab Cavity Cryostat, 14 Dec 2012 Design considerations Cooling arrangement for integration into cryo system Cooling arrangement for integration into cryo system Pipe sizes for steady-state and emergency venting Pipe sizes for steady-state and emergency venting Pressure stability factors Pressure stability factors Liquid volume, vapor volume, liquid-vapor surface area as buffers for pressure change Liquid volume, vapor volume, liquid-vapor surface area as buffers for pressure change Evaporation or condensation rates with pressure change Evaporation or condensation rates with pressure change Updated heat load estimates Updated heat load estimates Options for handling 4.5 K (or perhaps 5 K - 8 K) thermal intercept flow Options for handling 4.5 K (or perhaps 5 K - 8 K) thermal intercept flow Alignment and support stability Alignment and support stability Thermal contraction and fixed points with closed ends Thermal contraction and fixed points with closed ends 16

17. LHC Crab Cavity Cryostat, 14 Dec 2012 Cryomodule Pipe Sizing Criteria Heat transport from cavity to 2-phase pipe Heat transport from cavity to 2-phase pipe 1 - 1.4 Watt/sq.cm. is a conservative rule for a vertical pipe (less heat flux with non-vertical connection to helium vessel, analysis for tight spaces) 1 - 1.4 Watt/sq.cm. is a conservative rule for a vertical pipe (less heat flux with non-vertical connection to helium vessel, analysis for tight spaces) Two phase pipe size Two phase pipe size 5 meters/sec vapor “speed limit” over liquid 5 meters/sec vapor “speed limit” over liquid Not smaller than nozzle from helium vessel Not smaller than nozzle from helium vessel Gas return pipe (also serves as the support pipe in TESLA-style CM) Gas return pipe (also serves as the support pipe in TESLA-style CM) Pressure drop < 10% of total pressure in normal operation Pressure drop < 10% of total pressure in normal operation Support structure considerations Support structure considerations Loss of vacuum venting P < cold MAWP at cavity Loss of vacuum venting P < cold MAWP at cavity Heat flux as much as 4 W/cm 2 on low-T bare metal surfaces Heat flux as much as 4 W/cm 2 on low-T bare metal surfaces Path includes nozzle from helium vessel, 2-phase pipe, may include gas return pipe, and any external vent lines Path includes nozzle from helium vessel, 2-phase pipe, may include gas return pipe, and any external vent lines 17

18. Cryostat design options Use existing designs to the extent possible Use existing designs to the extent possible Two cavities, R&D nature of test Two cavities, R&D nature of test Provide relatively easy access to cavities, tuner, input coupler, HOM couplers Provide relatively easy access to cavities, tuner, input coupler, HOM couplers Several examples of such cryostats exist Several examples of such cryostats exist 1 – capture cavity 1 – capture cavity 2 – horizontal test cryostats 2 – horizontal test cryostats 3 – various top-loading designs 3 – various top-loading designs LHC Crab Cavity Cryostat, 14 Dec 201218

19. Cryostat design option examples – 1 Capture Cavity Capture Cavity Single cavity in a cryostat Single cavity in a cryostat Tension rod support Tension rod support Flanged vacuum shell heads Flanged vacuum shell heads Short cryostat allows attachment of tension rods to vacuum shell and transfer of load to the rods after insertion of cavity on simple tooling Short cryostat allows attachment of tension rods to vacuum shell and transfer of load to the rods after insertion of cavity on simple tooling Similar to what we saw from Niowave Similar to what we saw from Niowave LHC Crab Cavity Cryostat, 14 Dec 201219

20. Saclay/Fermilab Capture Cavity LHC Crab Cavity Cryostat, 14 Dec 201220

21. Cryostat design option examples – 2 Horizontal test cryostat (similar to “Chechia” at DESY) Horizontal test cryostat (similar to “Chechia” at DESY) Single cavity in a cryostat Single cavity in a cryostat Support post and frame beneath cavity Support post and frame beneath cavity Cavity rolls into position for ease of frequent changes Cavity rolls into position for ease of frequent changes Flanged and hinged vacuum shell heads Flanged and hinged vacuum shell heads LHC Crab Cavity Cryostat, 14 Dec 201221

22. Horizontal Test Cryostat LHC Crab Cavity Cryostat, 14 Dec 201222

23. Horizontal test cryostat LHC Crab Cavity Cryostat, 14 Dec 201223

24. Cryostat design option examples – 3 Top-loading cryostat Top-loading cryostat Argonne, Triumf, Daresbury, and others Argonne, Triumf, Daresbury, and others Rectangular sides Rectangular sides Structures hung from top plate Structures hung from top plate This design has some attractive features given the physical constraints of the SPS tunnel location and the R&D nature of these first tests This design has some attractive features given the physical constraints of the SPS tunnel location and the R&D nature of these first tests LHC Crab Cavity Cryostat, 14 Dec 201224

25. LHC Crab Cavity Cryostat, 14 Dec 2012 25

26. Design Approach – Cryomodule Schematic Shrikant Pattalwar Hi-Lumi Crab Cavity Engineering Meeting Dec 13-14, 2012 Fermi Lab TWO PHASE LINE 60 K RETURN 40 K FORWARD 4K (LHe) SUPPLY 2K (GHe) RETURN 4K GHe RETURN THERMAL SHIELD 40K TO 60K 5K THERMAL INTERCEPTS 4K PRE-COOL 2K HEX and a valve box could be a part of the module ?? Magnetic shield Outer Vacuum Chamber Shrikant Pattalwar LHC Crab Cavity Cryostat, 14 Dec 201226

27. Design Approach – Conceptual Model Shrikant Pattalwar Hi-Lumi Crab Cavity Engineering Meeting Dec 13-14, 2012 Fermi Lab 1000mm 2160mm 1000mm Triple tube cavity support system High order mode coupler Low order mode coupler RF input coupler SPS by-pass line 413mm 420mm 194 mm Shrikant Pattalwar LHC Crab Cavity Cryostat, 14 Dec 201227

28. Schedule Design process for new cryostat or cryogenic box is typically 2 to 3 years Design process for new cryostat or cryogenic box is typically 2 to 3 years After a complete definition of requirements, details of associated components (e.g., tuner, input coupler) are known, conceptual design (first year or more)... After a complete definition of requirements, details of associated components (e.g., tuner, input coupler) are known, conceptual design (first year or more)... ~1 yr engineering and design/drafting ~1 yr engineering and design/drafting ~1 yr procurement and fabrication ~1 yr procurement and fabrication LHC Crab Cavity Cryostat, 14 Dec 201228

29. Schedule Cavities to be installed in SPS in December 2015 Cryostat fully tested Q3-2015 Cryostat fully dressed Q2-015 Couplers available for cryostat Q1-2015 Couplers RF processed 50 kW SW cw all phases Q4-2014 Couplers assembled in clean room Q2-2014 onto test box Special processes FPC + Test Box (Cleaning, Brazing, EB welding, Gold plating, Ti coating) completed Q1-2014 All couplers + Test Box parts machined Q4-2013 All raw material delivered Q2-2013 All raw material ordered Q1-2013 (common) Coupler design completed February 2013 (+ Test Box !) 2013201420152016 LHC Crab Cavity Cryostat, 14 Dec 2012 February Eric Montesinos 29

30. LHC Crab Cavity Cryostat, 14 Dec 2012 SM18 tests Important to verify as much as possible before installation in SPS Important to verify as much as possible before installation in SPS Leak tight cold Leak tight cold Heat loads Heat loads RF performance of power couplers and cavities RF performance of power couplers and cavities Compatibility for cryogenic connections between SM18 and SPS Compatibility for cryogenic connections between SM18 and SPS 2 K – 4 K heat exchanger, valves 2 K – 4 K heat exchanger, valves Opportunity also to verify SPS flexible connections Opportunity also to verify SPS flexible connections 30

31. LHC Crab Cavity Cryostat, 14 Dec 2012 Conclusions Three cryostats, one for each cavity type Three cryostats, one for each cavity type Each will contain two cavities of the same type Each will contain two cavities of the same type Tight thermal constraints for SPS operation Tight thermal constraints for SPS operation Tight mechanical constraints for SPS installation Tight mechanical constraints for SPS installation Plus motion requirement Plus motion requirement Vertical cavity tests Vertical cavity tests Cryostat test at SM18 before tunnel installation Cryostat test at SM18 before tunnel installation Verify thermal performance within SM18 constraints Verify thermal performance within SM18 constraints Verify, as-installed in cryomodule, coupler and cavity RF performance at SM18 Verify, as-installed in cryomodule, coupler and cavity RF performance at SM18 31