1. CO2 cooling requirements for the IBL
D. Giugni.
NIKHEF, July 10th 2009
D. Giugni
NIKHEF July 09

2. Outline The ATLAS approach to CO2.
IBL Lay-out and implication to the cooling.
Roadmap toward a qualification of the CO2 cooling.
Requirements for the pilot CO2 plant.
D. Giugni
NIKHEF July 09

3. ATLAS vs. CO2
ATLAS has been considering, and still consider CO2, in any of the plant flavors, as a valuable and strong option for the IBL (insertable B-layer) cooling.
Nevertheless the detector expertise and the know-how belongs to evaporative system based on fluorocarbon. This cannot be ignored but it is not a matter of a “good feeling” vs. a system that is well known by the people involved.
Current systems is really complex. It has 204 cooling loops, ~60KW cooling power and it is much wider then what we are talking now for IBL.
I can bring up several examples where the evaporative fluorocarbon system has reserved unfair surprises despite of the excellent performances foreseen.
Most of them comes from the limited testing especially on the on-detector side. Problems are daughters of our (and I put myself at the top of the list) wishful thinking.
I really do not want to go through the same mistake twice:
Performances, reliability, soundness must be extended tested on real hardware.
D. Giugni
NIKHEF July 09

4. ATLAS vs. CO2 [2]
It is true that the so called “champagne” CO2 (NIKHEF style) does not start from scratch. A beautiful and reliable plant has been successfully delivered and commissioned for VELO.
Nevertheless, given our past experience, we want to approach the CO2 system in a practical and heuristic way. Certainly benefitting from the experience from other labs, trying to finding out a way of collaborating successfully.
Looking at the cooling beyond Phase I, CERN is willing to build up the expertise and the know-how on CO2 .
On top of the basic thermodynamic measurement on the boiling channel (that takes off ideally) today at NIKHEF, we are planning to build a pilot CO2 plant at CERN. The timescale is to provide recommendations at the TDR (Feb 2010) and support the cooling choice late 2010.
The question, now, is how to came to such a plant ready in due time
First step is to sort out the requirements:
D. Giugni
NIKHEF July 09

5. IBL Lay-out Number of staves is still unclear . They can be 13 or 14.
The recent estimate on the thermal transient during the bak-out leads to be optimistic about the module temperature. If it is confirmed by the tests, this solution becomes very appealing.
The two layout flavors shown here refer to a single and double pipe reversed turbine. Double pipe stave allows to have a full redundant cooling system.
CO2 foresees a “single” cooling line fan-out in multiple channels. The lost of the plant would leave the IBL completely without cooling.
A full redundant cooling system is not unrealistic for CO2!
Single pipe reversed turbine
Double pipe reversed
turbine
D. Giugni

6. On detector piping lay-out
Piping routing on the IDEP (Inner Detector End Plate) has been preliminary evaluated. The cold line seems to fit.
There are several other aspects to address:
Where is the manifold located? Inside the pixel volume or at PP1?
The integration process conflicts with the aim of minimizing the brakes (fittings).
Is a 7m long piping doable?
How do we handle the CTE mismatch?
Place should be compatible for having fittings only on the main line
D. Giugni
NIKHEF July 09

7. IBL CO2 cooling roadmap Measurement of the HTC and CHF at NIKHEF
Based on the testing pipes (see next talk).
Site: Nikhef
Date: NowOctober
Measurement of the stave thermal figure of merit.
Based on “functional” CO2 plant to test staves and local supports
Structure: DCP/Cryloab
Site: CERN
Date: October  Feb
System test CO2 plant indicatively in SR1
Based on finalized CO2 plant for the system test
Structure: DCP
Date: 2010 Feb July

8. CO2 pilot plant requirements
IBL does not need a reduced pressure in any section of the piping. For all the plant the MDP (Max Design Pressure) is 100bar.
Power must be enough to operate the entire detector in view of the final qualification on surface. Design Power is 1.5KW.
Nominal evaporation temperature is -40C but we foresees operating at room temperature +20C.
Need 4 different circuits tat can be operated singularly. Each of them will be manifolded accordingly to the needs.
All the four branches have the same evaporation temperature.
The location of the plant is, indicatively, the SR1 building next to point1.
D. Giugni
NIKHEF July 09