1. Second Meeting of the Material Budget & Engineering Working Group
feasibility of CO2 cooling with existing CMS pipework
13 March 2008
Hans Postema (CERN)

2. Re-use cooling pipes
Cooling pipes are installed as bottom layer on the vac-tank.
Covered by a vast amount of ECAL and Tracker cables.
Covered by a vast amount of Tracker optical fibres.
Re-installation of pipes will require an extremely long shutdown.
13 March 2008
Hans Postema (CERN)

3. YB0 with cables
13 March 2008
Hans Postema (CERN)

4. Inside the Vac-tank
13 March 2008
Hans Postema (CERN)

5. YB0 and PP1 view
13 March 2008
Hans Postema (CERN)

6. YB0, tower, balcony
13 March 2008
Hans Postema (CERN)

7. PP1 to tower routing
13 March 2008
Hans Postema (CERN)

8. All routes, Z+ view
13 March 2008
Hans Postema (CERN)

9. Top view UX cavern
13 March 2008
Hans Postema (CERN)

10. Summary of tubes
Between Tracker and PP1 3 m of tube with ID 10 mm, can easily be replaced
Between PP1 and Tower, 20 m of tube with ID 12 mm
Between Tower and Cooling station m of tube with ID 14 mm
All tubes are soft copper with 1 mm wall thickness
Tubes can run either 10 m up or down with respect to the Tracker
13 March 2008
Hans Postema (CERN)

11. CMS ladder dimensions 1mm ID Tube Q = 40 Watt Tube length = 2.5 meter
1.25 meter length
Cooling

12. CMS, use of existing tubes
CMS pipes = 14mmID
18kW =>1 liquid line & 6 vapor lines
1 loop assembly = 7 tubes
6 loop assemblies = 42 tubes for 108 kW
450 ladders per loop assembly
3150 ladders in total
Shut-down and start-up difficult due to
low allowed pressure of Cu-tubing
12.7bar = - 33’C
10 m static height: dP=1bar~2’C dT
120 g/s, 18kW
6 tubes
13.9bar
Dcooling=1mmID
Q=40W
TCO2=-30’C
MF= 0.26 g/s
dP= 600 mbar dT
450x
Liquid CO2
P=17.9 bar
T=-38’C
14.5bar
1 tube
17.9bar
17.7bar
Dcapillary=0.5mmID x 5m
dP=3.2bar
120 g/s liquid = 200mbar

13. Pressures
Elastic limit of soft copper 16 mm pipe corresponds to about 70 bar.
CO2 boiling point -20 C at 20 bar, thus moderate pressure during operation.
At +25 C, CO2 boils at 65 bar, this requires further investigation into a system with low pressure startup capability.
13 March 2008
Hans Postema (CERN)