Central vacuum valve in ALICE Pros and Cons ALICE TC –

20/11/13Central vacuum valve - Pros and Cons2

With valveWithout valve BakeoutDone with TPC in parking position  full proof of tightness of the pipe before moving TPC Done once MNF and RB24 pipe in place  a very first bakeout could be done with the TPC in parking position, however we lose one NEG activation ITS-MFT installation RB24 beampipe (and compensator magnet) can be removed Must be done with RB24 beampipe (and compensator magnet) in place (after bakeout) MNF access during EOY No risk if valve closedImperative to protect RB24 pipe in order to not compromise the vacuum in central and RB26 pipes Compensator magnet removal No actions on ITS-MFT-central pipe if valve is closed Implies to extract the ITS-MFT and re- bakeout the central and RB26 pipes BackgroundFactor 2 higher background (beam gas coming from left side) than without valve Less background Material budget in the fw region More materialLess material 20/11/13Central vacuum valve - Pros and Cons3

With valveWithout valve BakeoutDone with TPC in parking position  full proof of tightness of the pipe before moving TPC Done once MNF and RB24 pipe in place  a very first bakeout could be done with the TPC in parking position, however we lose one NEG activation ITS-MFT installation RB24 beampipe (and compensator magnet) can be removed Must be done with RB24 beampipe (and compensator magnet) in place (after bakeout) MNF access during EOY No risk if valve closedImperative to protect RB24 pipe in order to not compromise the vacuum in central and RB26 pipes Compensator magnet removal No actions on ITS-MFT-central pipe if valve is closed Implies to extract the ITS-MFT and re- bakeout the central and RB26 pipes BackgroundFactor 2 higher background (beam gas coming from left side) than without valve Less background Material budget in the fw region More materialLess material 20/11/13Central vacuum valve - Pros and Cons4

Ion pump and vacuum gauge Meeting with R.Veness, G.Schneider, M.A.Gallilee, J.Perez Espinos, W.Riegler and A.Tauro ( ) Ion pump needed to pump out non NEG gases (e.g. methane). There is one ion pump every 26 m max., and it seems not possible to remove the pump. It could be done in Al. Pirani gauge needed for safety. It tells whether it’s safe to open the valve. It could be moved to the tunnel (SR23 side). New valve fitted with a gauge. 20/11/13Central vacuum valve - Pros and Cons5

Backup slides

Al ion pump (ATLAS) 9 Jan 13A.Tauro7