1. CO2 cooling in CMS General overview 30 July 20101Hans Postema - CERN

2. Why CO2? Radiation hard Not electrically conductive, non corrosive Not flammable, not toxic Has excellent thermodynamic properties for micro- channels. Low dT/dP Low mass Low liquid/vapour density ratio Low viscosity High latent heat High heat transfer coefficient Environmental friendly 230 July 2010Hans Postema - CERN

3. Pressure advantage Intuitively, higher pressures seem a disadvantage but: Gas flow at higher pressures needs smaller pipe diameters Pressure drops due to flow become less significant, allowing smaller pipes Small pipes can easily support the required pressures 330 July 2010Hans Postema - CERN

4. Pixel barrel structure 430 July 2010Hans Postema - CERN

5. CO 2 Cooling Test Setup 30 July 20105Hans Postema - CERN PRESSURE GAUGE METERING VALVE OPTIONAL CAPILLARY TUBE DETECTOR TUBE WITH ELECTRIC HEATING MASSFLOW METER CO 2 BOTTLE WITH PLUNGER CONCENTRIC TUBE HEAT EXCHANGER VENT TO ATMOSPHERE PROPORTIONAL RELIEF VALVE WATER BATH HEATER

6. Straight Tube Results @ -10°C 30 July 20106Hans Postema - CERN

7. Cooling Pipes No space left in CMS to install new supply and return line for CO2 cooling We must reuse the exiting pipes since the currently installed cooling pipes are virtually impossible to replace People ask: “Is this really the case” Please have a look at the following slides 30 July 20107Hans Postema - CERN

8. Empty YB0 – far left 30 July 20108Hans Postema - CERN

9. YB0 – fully cabled 30 July 20109Hans Postema - CERN

10. YB0 - numbers Tracker cooling pipes below all the cables HB: 180 cables, 180 optical fiber cables EB: 1600 cables, 180 optical fiber cables Tracker: 3000 cables, 640 Optical fiber cables 9 month plus, installation time Removing and reinstalling ~10 year old EB cables is inviting trouble 30 July 201010Hans Postema - CERN

11. Re-use of installed pipes The currently installed pipes are OD=14 and OD=16 mm copper pipes with a wall of 1 mm Cannot be used for 2 phase CO2 cooling without special precaution But can be used when the system design takes care that pressures remain below a limit Avoiding 100+ bar pressures is also advantageous for detector design 30 July 201011Hans Postema - CERN

12. Storage tank The system contains a cooled storage tank When system is inoperative, all liquid is condensed in the tank, all warm components are filled with gas (Standard for cryogenic systems) A very similar system is used for the CDF COT flange cooling, same concept, different fluid, different temperature. See next slide 30 July 201012Hans Postema - CERN

13. Which pressures Strong request for detector operation with coolant at +15 C. Avoids condensation during the installation and testing phase. For this a safety valve setting at 57 bar, corresponding to +20 C seems acceptable. Normal operation is below 0 degree C, which corresponds to 35 bar 30 July 201013Hans Postema - CERN

14. Operation modes Normal operation, system cooled by commercial chiller, CO2 temperatures between 0 and -20 C, pressures 35 to 20 bar Testing during installation, system cooled by chilled water, temperature +15 C, pressure 50 bar Storage during shutdown, cooled by standard CERN chilled water system, temp +5 C, 40 bar 30 July 201014Hans Postema - CERN

15. Strategy (1) CO2 cooling plants cannot be bought off the shelf Relevant experience is not available in industry Current activities are generating the necessary experience “in house” Future CO2 cooling plants shall be designed and constructed “in house” 1530 July 2010Hans Postema - CERN

16. Strategy (2) Cooling plant shall be constructed early, leaving 1 year for commissioning on the surface and 1 year for installation in UX To avoid schedule constraints, one cooling plant foreseen for detector commissioning in TIF, and one for installation in the CMS cavern 1630 July 2010Hans Postema - CERN

17. Cooling plant 1730 July 2010Hans Postema - CERN

18. Including dummy load 1830 July 2010Hans Postema - CERN

19. 1930 July 2010Hans Postema - CERN

20. Conclusions Test results of the small tubes inside the detector show very good cooling performance Several re-circulating cooling plants are now operating successfully We need to get full understanding of the flow properties of the large diameter supply and return lines since they cannot be replaced by pipes that are better suited to CO2 cooling 30 July 2010Hans Postema - CERN20

21. Participating groups CERN – Atlas CERN – CMS CERN – PH-DT CERN – EN-CV CERN – Cryolab EPFL Lausanne Fermilab IPN Lyon NIKHEF – Atlas, LHCb PSI RWTH Aachen SLAC Atlas University Esslingen University Karlsruhe 2130 July 2010Hans Postema - CERN