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Below is a diagram of the cooling systems. Three separate, independent circuits are used.

• MCM air-cooling: Cooled air is split at the entry to the MVD. Some goes through the plenum below the barrel, where the MCMs of the strip detectors are housed. Some goes up around the MCMs of the pad detectors, crosses to the other side through the structural Al tube at the top of each MVD half, past the MCMs of the pad detectors at the other end, and back again to the fans and heat exchangers.
• Silicon air: Although the silicon does not generate any heat, a separate cooling system is provided. It allows us to cool the silicon in case of radiation damage, which leads to increased leakage current. This current is sensitive to silicon temperature.
• Voltage regulator water cooling: On the endcap mother boards are located a number of power control semiconductor devices ('low dropout regulators'). These are point sources of considerable heat, and are therefore best cooled with water. The water system is Cern's patented leakless design. Furtheremore, there are no water plumbing joints inside the MVD.