ILC GDE meeting Cryogenics

1. ILC GDE meetingCryogenics L. Tavian, CERN T. Peterson, Fermilab Bangalore, 10 March 2006

2. Contents • Sloped system comments • Cryoplant capacity and margin • Cryogenic unit length • Segmentation • Cryogenic system arrangement • Cryogenic plant architecture • Plan for cost estimate

4. Sloped system concerns • Want heat removal without bubbling or boiling • Saturated superfluid heat flux limit about 1 W/sq-cm • 54.9 mm dia down-pipe means 23.7 sq-cm or about 24 W per cavity can be transferred away • But a claim was made that surface area limit is 1/10 of that, 0.1 W/sq-cm, so 2.4 W/cavity limit • Hence, want to pool liquid in 2-phase pipe by means of dams in order to provide large surface area for evaporation • Conclusion in subsequent discussions -- dams not needed • Even just 2.4 W/cavity is enough, expect 1.7 W/cavity at 36 MV/m • Most experience does not support the claim of the surface area heat flux limit • Sloped system should not be a problem, within limits • LHC will run some areas with 1.4% slope • DESY will test sloped modules for XFEL

5. CERN LHC capacity multipliers • Cryo capacity = Fo x (Qd + Qs x Fu) • Fo is overcapacity for control and off-design or off-optimum operation and for cooling down • Fu is uncertainty factor on load estimates, taken on static heat loads only • Qd is predicted dynamic heat load • Qs is predicted static heat load ILC Proposal: Fo= 1.4 and Fu= 1.5

6. Heat Load evolution in LHC Basic Configuration: Pink Book 1996 Design Report: Design Report Document 2004 At the early design phase of a project, margins are needed to cover unknown data or project configuration change.

7. Cryogenic unit parameters

8. Cryogenic unit length limitations • 25 KW total equivalent 4.5 K capacity • Heat exchanger sizes • Over-the-road sizes • Experience • Cryomodule piping pressure drops with 2+ km distances • Cold compressor capacities • With 192 modules, we reach our plant size limits, cold compressor limits, and pressure drop limits • 192 modules results in 2.273 km long cryogenic unit -- 5 units per 250 GeV linac • Divides linac nicely for undulators at 150 GeV

9. Cryogenic unit segmentation and other cryogenic boxes • Segmentation issue is ultimately tied to reliability • RDR should include features for vacuum segmentation • Assume 4 cryo strings (48 modules, 563 meters) per segmentation unit • Cryogenic string supply and end boxes (cryogenic service modules), which may (should!) be separate from modules, are also required within the ILC linac

10. Full segmentation concept (ACD) • A box of slot length equal to one module • Can pass through cryogens or act as “turnaround” box from either side • Does not pass through 2-phase flow, so must act as a supply or end of a cryogenic string • Includes vacuum breaks • May contain bayonet/U-tube connections between upstream and downstream for positive isolation • May contain warm section of beam pipe • May also want external transfer line for 4 K “standby” operation (4 K only, no pumping line)

11. Cold devices • ~940 main linac modules per 250 GeV linac (so 940 x 2) • Pre-accelerators up to 5 GeV (1 electron, 1 positron) • ~10 special low-energy magnet/RF modules (x2) • 21 standard modules in each (x2) • Damping rings (1 electron, 2 positron) • Electron side -- 650 MHz SRF, about 15 cavities plus 200 m of CESR-c type SC wigglers = 1200 W total at 4.5 K • Positron side -- 650 MHz SRF, about 10 cavities plus 200 m of CESR-c type SC wigglers x 2 rings = 2000 W total at 4.5 K • RTML (1 electron, 1 positron) • 61 standard modules, equiv to 5 strings (x2) (possibly also crabs) • Superconducting solenoids (x2) • 200 meters of SC undulators in electron linac (~300 W) • SC magnets and crab cavities in interaction regions • Various cryogenic service modules • Several km of cryogenic transfer lines

12. Cryoplant location options(electron side) Undulators RTML Undulators

13. Cryogenic architecture For shaft depth above 30 m, the hydrostatic head in the 2 K pumping line becomes prohibitive and active cryogenics (e.g. cold compressor system) has to be installed in caverns (LBC), i.e. additional cost for cryogenics and civil engineering.

14. Cost Breakdown Structure A more precise layout including the location of the cold device is required for the cost estimate of the cryogenic system (impact on number of technical service modules and transfer line length)

15. Schematic layout vs integration layout (next step is incorporating real locations in cryo system design) Real location ?

16. LHC Helium Refrigerator Coldbox18 kW @ 4.5 K

17. LHC Helium Compressor Station

18. Covering Modified Claude cycle, no permanent LN2 precooling Capacity range 0.8 to 18 kW @ 4.5 K equivalent Iso-exergetic assessment of mixed cooling duties Not included LN2 precooler for cooldown of load Coldbox interconnection lines & pipework Process control hardware & software Best practical fit Cost = 2.2 x Capacity0.6 [MCHF 1998][kW @ 4.5 K] Cryogenic He RefrigeratorsCapital Cost

19. Specific Cost of Bulk He Storage *: CHF 1998 year (1): Purity non preserved; not including storage building (2): Not including HP compressors (3): Not including reliquefier

20. 2 MPa GHe Storage Vessels

21. He Compound Transfer Line • CERN experience return for compound lines: • From few 10’s of m up to several 10’s of km with singularities (steps, elbows, technical service modules…) • For large series, row material becomes one of the main cost drivers (e.g. variation on stainless-steel cost). • Cost • Standard length: between 5 to 15 kCHF/m for compound lines of ~600 mm external diameter depending on the unit length. • Singularities: Each singularity equivalent to 3 to 6 m of standard length.

22. Conclusions • Sloped system should not be a problem, within limits • 5 cryogenic units per linac • 192 modules per unit, 2.3 km long • Limited by plant size, cold compressor capacities and piping pressure drops • Next step is incorporating real locations in cryo system design -- needed for cost • Cost estimate based on LHC experience