Cooling of NA62 vacuum system November 11 th, 2014 E. Harrouch, EN-MEF, on behalf of the NA62 Vacuum Team

Outline  Summary of the installation  History  Consequences of a water cut EATM 2

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4 Blue tube vacuum system DN250 Turbo group Primary pumps He Compressors (for cryo pumps)

EATM Demineralized water network Raw water network Water cooling network 5

Current situation EATM One accidental water cut (Wednesday 22th of October). One planned on Tuesday 28 th of October. According to CV : You can expect around 5 water cut per year. Origin : Power cut, pressure drop (water leak, purge valve remained open …) 6

7 EATM Consequences For the DN250 turbo group : No consequences as long as P BT < mbar Primary pumping group: No consequences if it does not happen during pump down Cryo pumps: Compressor will stop, gate valve will close and cryo pump will enter into regeneration mode.

8 EATM The cryo pumps will need one day to be cooled down again. At the moment, it requires a local intervention. Consequences

9 EATM Risks For the turbo pump and primary pumping group : No particular risk. For the cryo pumps : In regeneration mode it requires nitrogen supply. If the power or nitrogen is missing. This could damage the cryo pump. Vacuum envelope P T1 T2 Purge gas (N2) inlet with gas inlet heater Heating jacket Cryosorber ≈ 15 K ≈ 50 K Roughing valve DN63

10 EATM 3 water network available in the ECN3 cavern : Demineralised water Raw water Fire brigade water network How to make the system safer

11 EATM No real advantage to switch from the demineralised water network to the raw water network. (same rate of failure) Use a similar system as it is done on the He Compressors in for COMPASS : Use of the drinking water network as backup. How to make the system safer