1. ILC GDE meeting Cryogenics
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
GDE Bangalore, Cryogenics, 10 March 2006

3. GDE Bangalore, Cryogenics, 10 March 2006

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
GDE Bangalore, Cryogenics, 10 March 2006

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
GDE Bangalore, Cryogenics, 10 March 2006

6. Heat Load evolution in LHC
Basic Configuration: Pink Book 1996
Design Report: Design Report Document 2004
Temperature level
Heat load increase w/r to Pink Book
Main contribution to the increase
50-75 K
1,3
Separate distribution line
4-20 K
Electron-cloud deposition
1,9 K
1,5
Beam gas scattering, secondaries, beam losses
Current lead cooling
1,7
Separate electrical feeding of MB, MQF & MQD
At the early design phase of a project, margins are needed to cover unknown data or project configuration change.
GDE Bangalore, Cryogenics, 10 March 2006

7. Cryogenic unit parameters
GDE Bangalore, Cryogenics, 10 March 2006

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 km long cryogenic unit -- 5 units per 250 GeV linac
Divides linac nicely for undulators at 150 GeV
GDE Bangalore, Cryogenics, 10 March 2006

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
GDE Bangalore, Cryogenics, 10 March 2006

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)
GDE Bangalore, Cryogenics, 10 March 2006

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 MHz SRF, about 15 cavities plus 200 m of CESR-c type SC wigglers = 1200 W total at 4.5 K
Positron side 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
GDE Bangalore, Cryogenics, 10 March 2006

12. Cryoplant location options (electron side)
Undulators
RTML
Undulators
GDE Bangalore, Cryogenics, 10 March 2006

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.
GDE Bangalore, Cryogenics, 10 March 2006

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)
GDE Bangalore, Cryogenics, 10 March 2006

15. Schematic layout vs integration layout (next step is incorporating real locations in cryo system design)
Real location ?
GDE Bangalore, Cryogenics, 10 March 2006

16. LHC Helium Refrigerator Coldbox 18 kW @ 4.5 K
GDE Bangalore, Cryogenics, 10 March 2006

17. LHC Helium Compressor Station
GDE Bangalore, Cryogenics, 10 March 2006

18. Cryogenic He Refrigerators Capital Cost
Covering
Modified Claude cycle, no permanent LN2 precooling
Capacity range 0.8 to 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] 4.5 K]
GDE Bangalore, Cryogenics, 10 March 2006

19. Specific Cost of Bulk He Storage
Type
Pressure [MPa]
Density [kg/m3]
Dead volume [%]
Cost [CHF*/kg He]
Gas Bag
0.1
0.16
300(1)
MP Vessel 2
3.18
5-25
HP Vessel 20
29.4
0.5
500(2)
Liquid
125 13
(3)
*: CHF 1998 year
(1): Purity non preserved; not including storage building
(2): Not including HP compressors
(3): Not including reliquefier
GDE Bangalore, Cryogenics, 10 March 2006

20. 2 MPa GHe Storage Vessels
GDE Bangalore, Cryogenics, 10 March 2006

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.
GDE Bangalore, Cryogenics, 10 March 2006

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
GDE Bangalore, Cryogenics, 10 March 2006