1. Environmental Conditions in the LHC Experimental Caverns JCOV Thursday 18 th March

2. ATLAS UX15 Cavern conditions specified in Technical Specification IT-2659/ST/LHC (summary in Engineering Specification LHC-UA15-ES-001, EDMS No. 313039) Heat Load = 180 kW Air flow rate = 60,000 m 3 /h Supply temperature = 17 °C Supply air humidity = 10 °C dew point temperature Temp. range in cavern = 18 °C (floor) – 28 °C (vault) Air displacement principle: cool air supplied at the bottom of the cavern (highest relative humidity) warm air at the extraction point at the vault

3. ATLAS Detailed simulations performed to study overall temperature gradients and local hot spots (“Thermal analysis of the airflow around the ATLAS muon barrel”). No simulation available for humidity distribution. Simulation made by ILK (on basis of 100 kW heat load) useful to illustrate humidity stratification. Requirement on relative humidity (< 70 %) respected.

4. CMS UXC55 Cavern conditions in same Technical Specification, IT-2659/ST/LHC. Heat Load = 100 kW Air flow rate = 45,000 m 3 /h Supply temperature = 17 °C Supply air humidity = 10 °C dew point temperature Temp. range in cavern = 18 °C (floor) – 26 °C (vault) Air displacement principle: cool air supplied at the bottom of the cavern (highest relative humidity) warm air at the extraction point at the vault

5. ALICE UX25 Cavern conditions in Engineering Specification LHC-UA-ES-0004 (EDMS No. 386351). Heat Load = 100 kW Air flow rate = 45,000 m 3 /h Supply temperature = 17 °C Supply air humidity = 10 °C dew point temperature Temp. range in cavern = 17 °C (floor) – 24 °C (vault) Air displacement principle: cool air supplied at the bottom of the cavern (highest relative humidity) warm air at the extraction point at the vault

6. ALICE UX25 Detector conditions in Engineering Specification LHC-UA-ES-0004 (EDMS No. 386351). Air flow rate = 6,000 m 3 /h Pressure head = 22,500 Pa Supply temperature = 17 °C Supply air humidity = 10 °C dew point temperature

7. LHCb UX85 Cavern conditions (UXD, detector area) in Engineering Specification, EDMS No. 351740 (not released). Heat Load = 50 kW Air flow rate = 22,500 m 3 /h Supply temperature = 17 °C Supply air humidity = 10 °C dew point temperature Temp. range in cavern = 17 °C (bottom) – 24 °C (vault) Air mixing principle: cool air supplied via grilles at 2 m from the bottom of the cavern warm air extracted via duct under cavern vault lower stratification, much more entrained air and secondary flow pattern

8. LHCb UX85 Cavern conditions (UXC, protected area) in Engineering Specification, EDMS No. 351740 (not released). Heat Load = 50 kW Air flow rate = 22,500 m 3 /h Supply temperature = 17 °C Supply air humidity = 10 °C dew point temperature Temp. range in cavern = 17 °C (bottom) – 24 °C (vault) Air mixing principle: cool air supplied via grilles at 2 m from the bottom of the cavern warm air extracted via duct under cavern vault lower stratification, much more entrained air and secondary flow pattern

9. All Experimental Caverns Supply air humidity: 10 °C dew point temperature Maximum humidity (extraction): 12 °C dew point temperature (high humidity alarm) No internal latent loads, humidity rise may come from water leaks or through-wall infiltrations, air infiltrations from annex spaces, etc. Drying capacity ( 20,000 m 3 /h, between 10 & 12 °C dpt ) max : 23 kg/h