1. Muon barrel cooling G. Aielli and J. Godlewski LS1 TC planning

2. Problem overview Cooling of the barrel toroid region. Definition of the problem a)Heat sources inside uniformely distributed (with exceptions) b)Barrel toroid tight chamber layout insulates it from the external ventilation c)Excess of temperature gradient due to stratification and convection 9°C from bottom to top (19 to 28°C) d)Excess of average temperature 24°C instead of 20°C e)Lowest temperature on TGCs (endcaps) 17°C Cathegory of interventions: 1.Local removal or shielding of the heat produced (a,b,c) 2.Geographical redistribution of the cooling power (b,c,e) 3.Overall increase of the cooling power (a,d)

3. Heat removal The trade off is to remove the heat of localized strong sources The removal of the distributed heat produced by each chamber has a limited result with respect to the resouces needed Targets highlighted: – PP2 is shielded but the shielding is not very efficient – There is a big mass of TRT power cables below PP2 at about 30°C which can be reduced/shielded – 22 diffusion pumps for the toroid coils very hot >50°C and unshielded New Muon chambers (they are blocking air flow). Once more we can not count on diffusion from outside to the inside of the barrel

4. Cooling power distibution Global intervention strategy: – Reduce as much as possible the EC outlets vent air flow and increase the HS outlets  done already. The main target of this intervention is to reduce the TGC sensitivity to the injected cold air – Remove cold air from the source and actively inject in the barrel. There are 2 installations already in place with different strategy: Ventilation pipe in sector 13 is taking cold air «for free» with a pump from the Level0 air, being already cold enough. The advantage is that you can have as much as you want without implication on the cavern ventilation system (ans safety…) Ventilation pipe installed at Level 8 on top of the detector, driving air directly from the top ventilation ducts. This is done passively at the moment and the air is injected in the most heated sectors on top. – Both these installations can be improved in therm of total cooling delivered and distribution

5. Sector 13 ventilation pipe Side c view The air is injected in sec. 13 BM and distributed along Z This is not optimal since this part is already cold The proposal is to bring the air as UP as possible toward sectors 1 and 9 BM and traslate the distribution pipe accordingly Optimal position to be defined

6. Top sector ventilation pipe Proposed modification to the present system: – Increase the overall air flow by applying fan inside the pipes. This can have concern ATLAS ventilation system and require discussion with EN-CV group – Make a finer distribution according to the scheme on the next slide. In facts we measure highly scattered temperature values on the top sectors depending on the diffusor position Top view Cold air Air diffusor

7. Proposal for air distribution in Muon Barrel sector 5 Fresh air into gaps between BML sector 5 and BMS sector 4 and 6 through perforated 200 mm ducts Fresh air into central part of the sector 5 400 mm main duct There should be symmetrical arrangement for sides A and C We should also check that the cold air impacts on the lower plane of the BML of sector 5

8. Increase of the cooling power This can be done by – Increasing the total air change rate, presently 60000 m^3/h. This could allow to increase the amount of gas deviated from the main ducts to the top sectors – Lowering the input temperature as much as possible compatibly with the TGC safety. – It seems there is room enough for bo the interventions