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Cryomodule Specifications and Design Overview

Cryomodule Specifications and Design Overview. LCLS-II 1.3 GHz Cryomodule. Tom Peterson 12 May 2015. Outline. Introduction , configuration and layout Documentation status FDR , differences from prototype High Q0 retention, cool-down Liquid helium management

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Cryomodule Specifications and Design Overview

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  1. Cryomodule Specifications and Design Overview • LCLS-II 1.3 GHz Cryomodule Tom Peterson 12 May 2015

  2. Outline Production Cryomodule Final Design Review, 12 May 2015 Introduction, configuration and layout Documentation status FDR, differences from prototype High Q0 retention, cool-down Liquid helium management Thermal design, heat loads, pressure drops Cryomodule interfaces Prototype tests Summary

  3. LCLS-II Linac • Thirty-five 1.3 GHz 8-cavity cryomodules • Two 3.9 GHz 8-cavity cryomodules • Four cold segments (L0, L1, L2 and L3) which are separated by warm beamline sections. Physics Requirements Document: “SCRF 1.3 GHz Cryomodule,” LCLSII-4.1-PR-0146-R0,4/30/2014 Original Release. Production Cryomodule Final Design Review, 12 May 2015

  4. The Cryogenic System Figure from LCLS-II-4.9-EN-0300 (ED0001995) LCLS-II CDS Relief System Analysis Production Cryomodule Final Design Review, 12 May 2015

  5. LCLS-II cryomodules: top level parameters Physics Requirements Document: “SCRF 1.3 GHz Cryomodule,” LCLSII-4.1-PR-0146-R0,4/30/2014 Original Release. Production Cryomodule Final Design Review, 12 May 2015

  6. LCLS-II Cryomodule Documentation, page 1 (more up-to-date list is LCLS-II-CryomoduleDocumentationList-10May2015-Links.xlsx) Production Cryomodule Final Design Review, 12 May 2015

  7. LCLS-II Cryomodule Documentation, page 2 Production Cryomodule Final Design Review, 12 May 2015

  8. LCLS-II Cryomodule Documentation, page 3 Production Cryomodule Final Design Review, 12 May 2015

  9. LCLS-II Cryomodule Documentation, page 4 Production Cryomodule Final Design Review, 12 May 2015

  10. LCLS-II Cryomodule Documentation, page 5 Production Cryomodule Final Design Review, 12 May 2015

  11. FNAL Team Center numbering for important components of 1.3 GHz CM (Preproduction & Production) Production Cryomodule Final Design Review, 12 May 2015

  12. 1.3GHz pCM-design and drawings status, May 2015 • Top-level assembly drawing is F10009945 • 3D NX model of 1.3GHz preproduction cryomodule ~98% • Status of drawings which are not approved and released yet: • instrumentation flanges (Done) • liquid level with instrumentation (Done) • finishing model of the magnet current leads (in progress) • HTC test in June will verify current lead design • some thermal intercepts (in progress) • Analyses to confirm intercept sizing are nearly complete • finalize lower 50K shield (Done) • magnetic shielding-new design (Done) • 2D drawings total: 936of ~1043 • total released 2D drawings: 664(some released drawings need to be revised) • need to finalize 2 of 4 “top level drawings”: Cold mass Assembly-F10009950 and 1.3GHz Cryomodule Assembly-F10009945 Production Cryomodule Final Design Review, 12 May 2015

  13. Some major requirements in terms of driving design Production Cryomodule Final Design Review, 12 May 2015 • Series configuration, TESLA style • Continuous insulating vacuum • No external parallel transfer line • 300 mm OD helium gas return pipe (HGRP) is “backbone” support • Helium vessel modified from ILC-style (including short end beam tube at both ends in the prototype cryomodule) for end-lever tuner • Modified tuner design • Thermal performance in CW operation • High heat loads, heat transport, helium flow rates • Input coupler for CW operation • 0.5% longitudinal tunnel slope • Liquid helium management • Retention of very high cavity quality factor (Q0) • Magnetic shielding • Cool-down constraints • Pressure safety A cryogenic system issue of which cryomodules play a major part

  14. SLAC Tunnel with 1.3GHz Cryomodule Production Cryomodule Final Design Review, 12 May 2015 • Tunnel size: 10x11 Feet • Tunnel slope: ~0.5%

  15. ILC / XFEL CM Modifications for LCLS-II (components) Functional Requirements Document: “1.3 GHz Superconducting RF Cryomodule,”LCLSII-4.5-FR-0053-R0,6/23/2014 Original Release. Production Cryomodule Final Design Review, 12 May 2015 • Component design – based on TESLA / ILC / XFEL designs • Cavities – XFEL identical • Helium vessel – XFEL-like (modified ILC with bellows at end for end lever tuner) • HOM coupler – XFEL-like • Magnetic shielding – increased from XFEL to maintain high Q0 • Tuner – XFEL-like end-lever style • Magnet – Fermilab/KEK design split quadrupole • BPM – DESY button-style with modified feedthrough • Coupler – XFEL-like (TTF3) modified for higher QL and 7 kW CW • Concerns based on global experience • Tuner motor and piezo lifetime: included access ports • Maintain high Q0 by minimizing flux trapping: new requirement – constraints on cool-down rate through transition temperature

  16. Differences between prototype and production CMs Production Cryomodule Final Design Review, 12 May 2015

  17. 1.3 GHz cavity(Preproduction & Production) More about dressed cavity from Chuck Grimm Production CM Cavity String Configuration pCM Cavity String configuration Production Cryomodule Final Design Review, 12 May 2015

  18. Cryomodule Thermal and Hydraulic Design Production Cryomodule Final Design Review, 12 May 2015 • LCLS-II CM is a modified TESLA/XFEL CM for CW mode operation • Thermal shields, intercept flow, and cryogenic supply and return flow in series through a string of cryomodules • Heat load range (design within the cryomodule includes generous margins) • 80 to 150 W per cryomodule at 2 K depending on local HOM deposition and cavity Q0 • A cavity may see as much as 25 W • Cost savings: Omit 5 K thermal shield • Simplification since large dynamic heat at 2 K makes such a thermal shield of marginal value • Retain 5 K intercepts on input coupler • Two-phase pipe is 100 mm diameter and closed at each end • 0.5% slope or 6 cm elevation difference over 12 m • 100 mm diameter two-phase pipe is nearly full at one end, nearly empty at the opposite end • Cryomodule (CM) thermal and hydraulic design is well advanced • Steady-state flows and upset conditions with venting analyses • Liquid supply valve for 2-phase liquid level, cool-down valve for “fast” cool-down

  19. Cryomodule flow scheme Cool-down valve for “fast” cooling is a BCR for high Q0 preservation Production Cryomodule Final Design Review, 12 May 2015

  20. LCLS-II Cryomodule (CM) Cryogenic Circuits 2.4 K subcooled supply Gas return pipe (GRP) Low temperature intercept supply Low temperatureintercept return High temperature shield supply High temperature shield return 2-phase pipe Warm-up/cool-down line Circuit (Line) Production Cryomodule Final Design Review, 12 May 2015

  21. Cryomodule image from 3-D model Production Cryomodule Final Design Review, 12 May 2015

  22. High Q0 requirement drives somenew design features Production Cryomodule Final Design Review, 12 May 2015 • We assume Q0 = 2.7E10 in our design • Magnetic shielding to keep < 5 mGauss • Probable new features necessary such as active external coils • High rate of cool-down looks necessary • VTS results were best with much as 2 – 3 Kelvin/minute through 9.2 K transition temperature • Key is high delta-T within Nb to “sweep out” magnetic flux • For fast cool-down, cool one cryomodule at a time • Create a closed-ended warm-up/cool-down manifold (line H) for each cryomodule so as to provide a cool-down/warm-up valve on each cryomodule • Design for 30 grams/sec of 5 Kelvin helium flow into cryomodule during cavity transition through 9.2 K • Analysis in backup slides • Retain original plan for uniform cooling of bimetallic joints

  23. Cool-down requirements • We must cool slowly from 300 K until most thermal contraction is complete (around 80 K). Cool-down rates (dT/dy and dT/dt) based on DESY measurements and analysis, in order to limit stresses on the support posts, must be limited in the Gas Return Pipe (GRP) • GRP vertical gradient is < 15 K • GRP longitudinal gradient is < 50 K • GRP cool-down rate is 10 K/hr • May start fast cool-down at 80 K or colder • “Fast” means 2 – 3 K/minute (“slow” < 0.5 K/minute) (reference: Anna Grassellino’s presentation) • Since thermal shield is ~35 K – 55 K, in the following analysis use 40 K delta-T at 3 K/minute = 13 minutes for transition from thermal shield temperature to below the niobium 9.2 K critical temperature Production Cryomodule Final Design Review, 12 May 2015

  24. LCLS-II Cryomodule Volumes • Fast cool-down of one cryomodule implies replacing 200 liters of helium volume as quickly as possible. • From the previous slide, we want to replace those 200 liters, starting at 40 K, with helium at ~ 5 K in 13 minutes. • Flow into the cryomodule at 15 liters/minute = 31 grams/sec liquid helium in liquefier mode. (~2 liters/min for each helium vessel) • 31 g/s sets cool-down valve size Production Cryomodule Final Design Review, 12 May 2015

  25. Cryogenic plant capacity (Cryo Plant Performance Sheet from Dana Arenius, August 5, 2014) Production Cryomodule Final Design Review, 12 May 2015 • In liquefier mode (supplying 4.5 K, receiving back warm helium gas), 31 grams/sec is no problem. • However, 4 cryomodules would require 4 x 31 = 124 gr/sec, about the limit of cryogenic plant production • L3 has 20 cryomodules cooled in parallel • 31 grams/sec per cryomodule would not be available • Need to focus cooling on a few cryomodules

  26. Conclusion for cool-down concept Production Cryomodule Final Design Review, 12 May 2015 • Required cool-down rate can be provided with our design • “Fast” cool-down comparable to single cavity tests can be provided in a cryomodule • Cryogenic plant can provide the flow for a few cryomodules at a time • Capillary tubes and other pipes can carry the flow • Note that line H (cool-down / warm-up line) exists only in the cryomodules and is eliminated from the distribution system. • Implementation . . . • Isolate Line H (cool-down / warm-up line) for each cryomodule and provide each cryomodule with its own cool-down valve, supplied from Line A (helium supply)

  27. Liquid helium management Production Cryomodule Final Design Review, 12 May 2015 • High heat loads (~80 Watts per cryomodule at 2.0 K) • 0.5% tunnel slope downward in beam direction • Careful design for liquid helium management • Keep liquid helium out of the 300 mm HGRP • Be sure cavities are covered with liquid with plenty of allowance for liquid level control in the 2-phase pipe

  28. All the dimensions, for reference Production Cryomodule Final Design Review, 12 May 2015

  29. Production Cryomodule Final Design Review, 12 May 2015

  30. Keep liquid helium out of HGRP Totally full 2-phase pipe just starts to spill into the 300 mm HGRP. But the connection from 2-phase pipe to HGRP is only at the center of the cryomodule, where the 2-phase pipe is half full. Liquid level there is 17 mm below the bottom of the 300 mm HGRP. (See next slide for dimensions.) Production Cryomodule Final Design Review, 12 May 2015

  31. But also be sure cavity is covered with liquid helium Bottom of the 2-phase pipe ID is 25 mm above the helium vessel ID top. Helium vessel is full to the top with any liquid in the 2-phase pipe. Center of the 2-phase pipe is 17 mm below the bottom of the HGRP. Production Cryomodule Final Design Review, 12 May 2015

  32. Connection from 2-phase pipe to 300 mm HGRP Connection from 2-phase pipe to 300 mm HGRP is 650 mm upstream (in beam direction) from center, up hill from center Production Cryomodule Final Design Review, 12 May 2015

  33. System Pressure Drops Production Cryomodule Final Design Review, 12 May 2015 • Pressure drops must be analyzed for each helium flow path to ensure that steady-state operation matches system design and that non-steady conditions (cool-down, emergency venting, warm-up) are properly handled • Input variables include line size, • Allowable temperature rise, • Allowable pressure drop • Heat load (temperature rise and heat load  mass flow) • Maximum allowable pressure for emergency venting • Matching cryomodule/distribution system to the cryogenic plant

  34. Pressure drop analysis for cool-down lines Production Cryomodule Final Design Review, 12 May 2015

  35. Two phase pipe pressures and vapor velocities Production Cryomodule Final Design Review, 12 May 2015

  36. Heat loads and cryogenic plant size Production Cryomodule Final Design Review, 12 May 2015 • Heat loads are carefully evaluated • Input from various groups including beam dynamics, RF cavity performance, input couplers, cryomodule design, magnets and current leads, distribution system • These are tabulated as “best estimates” meaning no margin added. These are the expected values • Then also an uncertainty factor must be applied • Heat load x uncertainty factor = maximum anticipated • Uncertainty factor evaluation should be quantitatively based on measurements and statistics • These then provide input to the cryogenic plant design and sizing • Temperature and pressure constraints agreed upon by various cryogenic system designers provides additional input • Combinations of heat loads (e.g., static only, static +RF, static + RF + beam) provide various “modes” for cryogenic plant operation

  37. Simplified Heat Load Diagram Production Cryomodule Final Design Review, 12 May 2015

  38. CM Static Heat Load • Basis of estimate: • Carlo Pagani, 2nd ILC Acc. Workshop, 8/16/2005 (TTF measurements at DESY) • X.L. Wang, et. al., TTC 2011 (CMTB measurements at DESY) • B. Petersenet. al., XFEL predicted based on measurements and analyses • N. Ohuchi, S1-G-report(Thermal Test).doc (S1-Global measurements at KEK) • Then add static heat estimate for items unique to LCLS-II such as cool-down valve, increased copper coating on input coupler, heavier HOM cables, etc. Production Cryomodule Final Design Review, 12 May 2015

  39. 2 K heat in first few cryomodules 94% From LCLScryoHeat-27April2015-100percent.xlsx Production Cryomodule Final Design Review, 12 May 2015

  40. Most recent estimate of heat loads From: LCLScryoHeat-27April2015-100percent Spreadsheet based on recent beam dynamics analyses from Andrei Lunin and input from Chris Adolphsen. Not yet formally documented in requirements or engineering notes. Production Cryomodule Final Design Review, 12 May 2015

  41. Cold compressor flow versus average cavity Q0 Approx limit for two cryogenic plants Underlying analysis is from an older heat load estimate, but changes are less than 10%, and this illustrates the impact of Q0. Approx limit for one cryogenic plant Production Cryomodule Final Design Review, 12 May 2015

  42. Two cryogenic plants, heat load limits Production Cryomodule Final Design Review, 12 May 2015 A design goal for cryomodules has always been that no part of a cryomodule be the “bottleneck” for heat transfer. In other words, we always design such that one can take full advantage of the maximum expected total cryogenic plant capacity. At project start, we selected a 100 mm OD nozzle from the helium vessel and 100 mm OD 2-phase pipe to accommodate large 2 Kelvin heat loads. We also retained the large thermal shield and thermal intercept lines corresponding to TTF/FLASH experience.

  43. Line sizes Production Cryomodule Final Design Review, 12 May 2015

  44. Helium II heat transport within the helium vessel Production Cryomodule Final Design Review, 12 May 2015

  45. Connection diameter versus heat flux 95 mm LCLS-II 55 mm XFEL XFEL Helium vessel is designed for heat loads of up to around 40 Watts, well in excess of our maximum anticipated of 25 Watts. Production Cryomodule Final Design Review, 12 May 2015

  46. Conductive heat flow to helium vessel end must be removed via helium II heat transport so as to keep Nb end groups cold. Analysis and tests at HTS show more than sufficient heat removal throughout the helium vessel. Production Cryomodule Final Design Review, 12 May 2015

  47. "LCLS-II Cryomodule External Interfaces" (LCLSII-4.5-IC-0372-R0, ED-0002307, Yun He) Production Cryomodule Final Design Review, 12 May 2015

  48. Cryomodule interfaces – alignment fiducials LCLSII-2.5-IC-0056-R1 (ED-0002307), Interface Control Document, “Accelerator Systems to Cryogenic Systems” Production Cryomodule Final Design Review, 12 May 2015

  49. Cryomodule interfaces – beam tube interconnect, HOM absorber LCLSII-2.5-IC-0056-R1 (ED-0002307), Interface Control Document, “Accelerator Systems to Cryogenic Systems” Production Cryomodule Final Design Review, 12 May 2015

  50. Cryomodule interfaces – RF power input coupler LCLSII-2.5-IC-0056-R1 (ED-0002307), Interface Control Document, “Accelerator Systems to Cryogenic Systems” Production Cryomodule Final Design Review, 12 May 2015

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