# Presentation: 533345

## A Preliminary Look at the ILC Cryogenic System 

- Tom Peterson, Fermilab
- ILC R&D Meeting
- 8 February 2006

## ILC 500 layout

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Slide 3

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## ILC modules and cryogenic system are closely based on the TESLA Technical Design Report (TDR)

- TESLA TDR is available online (see references)
- 9-cell niobium RF cavities at 1.3 GHz and 2 Kelvin are the primary accelerating structures
- Cavities are assembled into a cryostat called a “cryomodule” or “module”
- ILC module concept is still the TDR module, except 8 cavities instead of 12 per module
- TDR cryogenic system concept is retained

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## ILC cryogenic system effort is a very active collaboration 

- CEA Grenoble, CERN, DESY, Fermilab, Jefferson Lab, KEK, SLAC
- The concepts presented today represent the work of many people at these laboratories
- Previous input from industry for the TESLA effort and for LHC is also important

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## 1.3 GHz, 9 cell, Nb RF Cavity

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## TTF cryomodule

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Module end

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Generation 4, T4CM

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Slide 10

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## ILC cryogenic system overview (main linac)

- Revising and resizing the TESLA cryogenic concept
- Saturated He II cooled cavities @ 2 K
- Helium gas thermal shield @ 5 - 8 K
- Helium gas thermal shield @ 40 - 80 K
- Two-phase line (liquid helium supply and concurrent vapor return) connects to each helium vessel
- Two-phase line connects to gas return once per module
- A small diameter warm-up/cool-down line connects the bottoms of the He vessels (primarily for warm-up)
- Subcooled helium supply line connects to two-phase line via JT valve once per “string” (12 modules)

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Slide 12

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## 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 1.2% slope
- DESY will test sloped modules for XFEL

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Module heat estimates

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Module predicted heat loads

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Module pipe sizes increase

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## (Increase

- diameter
- beyond
- X-FEL)

- diameter
- beyond
- X-FEL)

- (Review
- 2-phase pipe
- size and
- effect of slope)

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Slide 18

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Cryo-string

- Now 12 cryomodules per string,
- totalling 140 m

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Cryogenic unit 16 strings per cyrogenic unit, so 192 modules per cryo unit (47 GeV) 

- Cryogenic unit 16 strings per cyrogenic unit, so 192 modules per cryo unit (47 GeV)

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## CERN LHC capacity multipliers 

- Cryo capacity = Fo x (Qd + Qs x Fu)
- Fo is overcapacity for control and off-design or off-optimum operation
- Fu is uncertanty factor on load estimates, taken on static heat loads only
- Qd is predicted dynamic heat load
- Qs is predicted static heat load

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Cryogenic unit parameters

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## 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 are hitting our plant size limits, cold compressor limits, and pressure drop limits

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Cryogenic unit segmentation and other cryogenic boxes 

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

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## 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)

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Lengths and packing factor (from spreadsheet originated by Chris Adolphsen and revised by Tom P.)

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Cryogenic unit packing factor 

- About 0.7 active RF length/total length
- Cryo boxes can be very short along the length of the linac if they have appendages to the side for valves, heat exchangers, liquid helium reserviors, etc.  But these then require alcoves.  Is this better than running the TBM slightly further?
- Cryo boxes can be incorporated into modules, improving the packing factor, but creating dozens of odd and special modules.  (We are keeping cryogenic boxes separate.)

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## ILC 500 cryogenic system overview for main linacs

- 10 large cryogenic plants (5 per linac)
- Approximately 2.3 km unit lengths
- Each cryogenic plant of about the maximum size -- equivalent to about 25 kW at 4.5 K
- Each plant about 5.2 MW “wall plug” power
- ILC 500 main linac cryogenics about 52 MW total

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## ILC cryogenics is more than these main linac cryogenic units

- ILC will have many other cold devices other than these regular linear patterns of main linac cryogenic modules
- Most work so far has focused just on a simplified view of the main linac cryogenics

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Cold devices 

- ~940 main linac modules per 250 GeV linac (so 940 x 2)
- Pre-accelerators up to 5 GeV (2 of these)
- ~10 special low-energy magnet/RF modules (x 2)
- 61 standard modules, equiv to 5 strings (x 2)
- 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
- 200 meters of SC undulators in electron linac (~300 W)
- SC magnets and crab cavities in interaction regions
- Various cryogenic feed, end, and transition boxes
- Several km of cryogenic transfer lines

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## BCD Description -500 GeV Layout- (Slide lifted from “Positron Source Configuration” by KURIKI Masao and John Sheppard, January 2006.Cryogenic device description in red added by Tom Peterson)

***Up to about 500 MeV via special SRF cavity/magnet modules totaling about 25 m x 20 MV/m***
***Then up to 5 GeV with 21 standard SRF modules***

***Standard modules (starting at 5 GeV) ***

***650 MHz SRF, about 10-15 cavities plus 200 m of CESR-c type SC wigglers, all 3 damping rings***

***200 m of SC undulators***

***Standard modules***

***Up to about 500 MeV via special SRF cavity/magnet modules totaling about 25 m x 20 MV/m***
***Then up to 5 GeV with 21 standard SRF modules***

***RTML includes ***
***SC solenoids ***
***plus 61 SRF modules***

***RTML includes ***
***SC solenoids ***
***plus 61 SRF modules***

***SC magnets and crab cavities ***
***               ******(no quatities yet) ***

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Slide 32

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Cryogenic system intertwined with linac lattice and conventional facilities

- For example, warm beam tube sections could go into segmentation boxes
- Conversely, we would try to locate ‘breaks” in the cryogenic system at interruptions in the lattice
- Some flexibility with respect to unit lengths and segmentation lengths
- RF unit of 3 modules should not be broken
- Prefer to keep cryo strings (12 modules) unbroken, but a 9 or 15 module string is possible
- Can try to locate plants at other above-ground facilities

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## ILC cryogenic system inventory

- Since we have not counted all the cryogenic subsystems
- and storage yet, ILC probably ends up with a bit more
- inventory than LHC

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Cryoplant concept

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Slide 36

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## Size comparison to TESLA TDR

- TESLA 500 TDR had 7 large cryoplants
- 5 at about 5.2 MW and 2 smaller
- ILC 500 looks like about 12 large cryoplants
- 10 at about 5.2 MW and 2 smaller
- Dynamic load up with gradient squared (length reduced by gradient), larger multipliers, lower plant efficiency
- Costs increase roughly linearly with increasing cryoplant power when we are pegged at the 25 KW plant size.
- Increased heat means adding plants, shortening strings, etc., so not the 0.6 or 0.7 power correlation with power at these levels of load.

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## ILC cryogenics -- open issues 

- Cryogenic loads outside of the main linac cryomodule strings (magnets, DR RF, etc.)
- Multiplier factors for sizing system
- High flow rates (about 50 times TTF flows)
- Segmentation philosophy (minimal or more)
- Reliability estimates
- Trustworthy predictions for module strings will require more experience with this technology
- LHC experience will tell a lot about reliability of a large-scale 2 K cryogenic system similar to ILC
- Upgrade heat loads and scenarios
- At 35 MV/m estimate 50% more heating

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting

## References 

- TESLA TDR -- online as TESLA Report 2001-23 at _[http://tesla.desy.de/new_pages/TESLA/TTFnot01.html](http://tesla.desy.de/new_pages/TESLA/TTFnot01.html)_
- Navigate to other TESLA and TTF documents going back to 1993 from the same web page
- ILC BCD documents
- http://www.linearcollider.org/wiki/doku.php?id=bcd:bcd_home
- bcd:main_linac:ilc_bcd_cryogenic_chapter_v3.doc
- ILC presentations
- Navigate from ILC home page via “Calendar/Past Events” and “Calendar/GDE Meetings”
- http://www.linearcollider.org/cms/?pid=1000012

- Tom Peterson

- 16-17 January 2006       Cryomodule Meeting