1. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 1 The ALICE water cooling systems A.Tauro

2. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 2 Outline ALICE cooling organization Overview of the ALICE water cooling systems Main problems found during the commissioning of the detectors –TPC –ITS Solutions adopted case by case Conclusions

3. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 3 ALICE cooling organization Cooling coordinator Cooling coordinator Detector expts TC TS-CV/DC Cooling coordinator: –Provides the interface between the cooling experts/TS-CV/external companies and the technical coordination (TC) –Responsible for the installation and testing of cooling services –Follows the commissioning stages Sub-detector cooling experts: –Provide technical specifications –Perform prototyping and/or mock-up tests –Commission the final system TS-CV/DC: –In charge of the fabrication, installation, operation and commissioning of the cooling plants Cooling plant Cooling services CERN techs or ext comp

4. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 4 Updates and reviews Regular status updates: –Installation -> weekly planning meetings –Commissioning -> daily commissioning meetings –Technical board and technical forum Cooling reviews dedicated to each sub-detector aiming at discussing: –Detector protection and safety (interlocks, HW protections, relief valves,…) –Cooling performances –In case of problems -> engineering change requests (re-routing of lines, cooling plant modifications)

5. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 5 Example: ALICE TB June ‘08 PLANTDCSINTERLOCKREMARKS TPC FEE Some faulty heaters → reparation in June OK P → Plant Plant → LV (to be tested) Cavitation in some lines TPC RR Tank release valve must be replaced Need to integrate conductivity measurement P → TPC FEE plant (to be checked) Low efficiency FMD OKOK (same as TPC) P → Plant Plant → LV, HV - TOF Need calibration of chilled water valve Tank level transmitter replacement OK Plant → LV (to be tested) Overpressure is not an issue PHOS FEE OKNO P → DSS → Plant (will be installed in June) Detector T=30°C No safety devices PHOS CRY OK NO Improve line insulation

6. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 6 Example: ALICE TF Oct ‘07 Pressure testWater cleaningRemarks TRDJan 07: 10 SRsSep 07: 6 SRs Upper sectors after TPC to IP HMPIDFeb 07Filter cleaned TOFAug 07: 4/6 crates, 1/6 FEEFittings/pipes required TPC Jan-Aug 07: C side, MNF Jun 07: A side Only MNF missing Pressure test/cleaning was repeated after rerouting PHOS- EMCAL Aug 07 Pressure test for PHOS crystal pipe not done SDD+SSDApr 07 Jun 07 MNF: Sep-Oct 07 Fine mesh filter (50um) SPDApr 07Jun 07-

7. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 7 The ALICE experiment forward muon spectrometer Central detectors

8. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 8 The L3 magnet in 2006…

9. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 9 ALICE front view

10. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 10 …and how it looks like now

11. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 11 Location of the cooling plants in the UX25 cavern TOF, EMC, CPV, PHOS TRD TPC HMPID SSD & SDD SPD PHOS

12. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 12 Services through the L3 door

13. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 13 Installation of pipes in the ALICE cavern Installation: 1 and ½ year, 7 teams, ~20’000 mt of pipes (40% stainless steel), ~3700 press fittings Test: about 500 over- pressure tests (~3’400hrs in total)

14. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 14 ALICE cooling plants Cooling plants: 7 units (5 water, 2 evaporative). Most of them are shared between detectors 5 produced by TS/CV-DC, 2 outsourced (Italy, Russia) PHOS is the only -25°C, all the others work at +16,+18°C Leakless operation First unit (SPD) delivered beginning 2006, last one (PHOS) beginning 2008 Total value of cooling plants >1MCHF

15. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 15 ΔP return ΔP supply ΔP detector P pump P tank h P in < P atm P out Jose Direito TS/CV/DC, 13.05.2008 The leakless operation It works only if P in < P atm Not all the loop is under- pressure!!! ΔP detector vs flow must be known ΔP return should be calculated

16. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 16 The TPC cooling

17. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 17 Temperature uniformity across the TPC volume N e /CO 2 is a ‘cold’ gas, with a steep dependence of drift velocity on temperature Uniformity of the temperature field must be extremely good (ΔT ≤ 0.1 K) 18x2 trapezoidal read-out chambers each one consuming 720W Complex system of heat screens and cooling circuits Heat screens: –outer radius toward the TRD –inner radius shielding from the ITS services –readout chamber bodies shielding from the FEE heat dissipation –FEE towards the outside Cooling circuits: –resistive potential dividers –front-end electronics

18. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 18 Front end electronics cooling pipes 0.5 mm copper tubes connected to 3 mm Si-tubes, without clamp or bracket Connection tested to withstand > 2 bar overpressure. But… … it could happen that the pipes are not properly plugged after an intervention for which they have to be disconnected -> what happen if one hose become disconnected ?

19. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 19 Test with dummy sector Test with dummy sector done in 2007 in the UX25 cavern Demonstrates that if a Si-pipe bunches-off there is a leak inside the chamber The plant takes 40s from the leak before stopping the water circulation -> P sensors installed on each chamber input line Continuous monitoring of pressures to verify underpressure operation Exceeding the threshold would immediately trigger an ALARM and stop circulation 40 s

20. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 20 “Cavitation” problem For some sectors it has been observed ad audible noise coming from the pipes These sectors exhibited a Pout < 50 mbar “Cavitation”, potentially dangerous condition. Increase of the flow resistance due to bi-phase liquid P threshold Increasing the tank pressure solves the problem but then makes the startup impossible Startup: need to kick up the pressure in order to get rid of the air in the pipe Solution: switch from startup tank pressure (e.g. 350 mbar) to running mode (e.g. 500 mbar)

21. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 21 Routing of cooling lines pressure sensor threshold Siphons in lines In some sectors there was no flow The reason was the presence of important siphons in the lines These lines have been re-routed sectors with new routing After re-routing of these lines the problem was solved

22. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 22 New lines installed Re-routing of TPC lines

23. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 23 ROC temperatures

24. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 24 Skirt temperatures

25. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 25 The laser system is used for precise position inter-calibration for the readout chambers and allows online monitoring of temperature and space-charge distortions, both of the order of a few mm

26. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 26 The ITS cooling

27. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 27 Layout of the ITS Only SPD uses C 4 F 10 coolant –low material budget, long-term stability against corrosion, chemical compatibility, minimal temperature gradients, cooling duct temperature above the dew point SDD and SSD share the same (water) cooling plant ITS uses stainless steel pipes

28. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 28 SPD commissioning Extensive (2 years) pre- commissioning in the lab –In normal operation, if a sudden failure of the cooling were to occur, the temperature at the module would increase at a rate of 1 °C/s –Continuous monitoring and a fast, reliable safety interlock on each module are therefore mandatory DCS and interlocks also tested in the lab Problems encountered in real installation –Low or zero flow in some loops. Due to different pipe layout with respect to lab –Still some liquid back into compressor. Heaters added

29. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 29 The SSD cooling Two thin (40 μm wall thickness) phynox tubes

30. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 30 The SSD FEE chips

31. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 31 50um filter150um filter Cleaning of the lines. June ‘07 In June 2007, before connecting the ITS to the cooling plant the pipes were cleaned by circulating water Found metal chips, dust particles which could have damaged the detector Water circulation continued for several days Filters of different mesh replaced at every time -> lesson learnt: use extreme care during pipe installation. Plug them before connecting the detector

32. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 32 Water leak. July ‘07 In July 2007, after 2 days of run with the nominal flow, a water leak was detected inside the ITS barrel (probably due to an open in the SDD region) Mylar foil acted as drain, water level not high enough to reach ladders In order to be leak proof, it was then decided to allow to work only in sub-atmospheric region inside the detector As for the TPC, pressure sensors were introduced in order to read the pressures at the detector

33. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 33 Problems and solutions When lowering the tank pressure to be underpressure at the detector, the “cavitation” problem appeared –Solution: 1) re-routing of some lines, 2) changing the inner pipe diameter Given the different routing of the lines, the flows amongst the loops were not equalized –Solution (SDD): upgrade the plant with flowmeters and pressure regulators –Solution (SSD): install balancing valves on input-output lines SSD and SDD have different flows and different ΔPdetector -> each one found an optimum value for Ptank and Ppump –Solution: install back-pressure regulators (SSD) + input pressure regulator (SSD) to decouple as much as possible the two systems The loops were difficult to drain –Solution: install bypass into cooling plant and manual valves in each line

34. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 34 Add 3 lines 16/18 till here Add 2 lines 16/18 till here Add 5 lines 16/18 Add 3+2 lines 16/18 Add 5 lines 16/18 The new lines Cost: 50KCHF

35. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 35 The SSD-SDD plant upgrade Cost of the upgrade: 150KCHF By-passes for Circuit Draining Two actuated valves on the common returns with remote positioning control to decouple return pressure from the SDD Pressure regulator for the SSD Manual valves on all SSD returns and supplies 5 enlarged return valves+ forks for the 18mm OD SDD pipes Pressure regulators for SDD Flowmeters for SDD

36. 30/10/2008Engineering Forum on Cooling for the LHC Detectors 36 Conclusions The ALICE cooling organization has been described. The cooling coordinator acting as a reference for all the cooling matters The leakless operation is effective only if Pin<Patm and it doesn’t guarantee that there are no leaks P sensors are fundamental in leakless systems. They should be part of the design of the cooling system It is fundamental to measure ΔPdetector vs flow and to have a good estimate of ΔPreturn. Piping inside the detector must be robust An optimized routing of the lines is crucial to minimize the impedance and to avoid siphons. Max care must be taken in the cleaning procedures Test test test is always the key