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VELO Vacuum Basic Operations

Vacuum Overview from FSM

  • From the ECS we can view the status of the vacuum system. However, all actions on the vacuum can only be performed by the vacuum group.
  • Open the main VELO ECS as described here
  • Navigate from the top level to the cooling status panel: VELO_TOP > VELO_DCS > VELOA_DCS > VELO_VACUUM > veloVacPLC
  • This panel gives an overview of the vacuum pressures and the whether neon is present. Click the "Detailed View" button for more info.
  • vac-overview.png

Detailed view the VELO vacuum system under beam conditions


  • Read the Vacuum Overview section directly above first.
  • Click on "Show Details/Hide Details" (left top) to get information of more/fewer vacuum meters.
  • The most important ones are the 4 red encircled ones in the screenshot below: PE411 and PE412 give the pressure in the beam volume in mbar. The pressure in the detector volume of the VELO is given by PE421 and PE422.
  • The status of the sector valves VVFSF.33.1L8.X and VVGST.198.1R8.X is displayed at the left/right side of the beam pipe.
  • The overall state of the vacuum system is represented by the field "Current state" on the bottom of the panel. The state "Ready for Beam" is what you need, from the vacuum point of view, to permit injection of beams into LHC.

Trend plots of the pressures in the detector volume, beam volume and LHC at either side of IP8 can be obtained in the following way:

  • Left-click button "Open Graph Select' in the top left corner
  • Select "+VEDCSVMC" << "VacuumSummary"
  • left-click in this last field
  • right-click selected field "Vacuum Summary"
  • left-click in the selected field "view"
  • A Trending Page should pop up with in the top figure the detector pressures of PE421 and PE422. In the middle figure the ones of the beam volume are displayed, i.e. PE411 and PE412. In the lower plot the reading of three LHC gauges, located just behind the sector valves, are shown. See also the readout of the most recent values in blue and red below the figures. You can change this period by means of the "Time Range" tab in the top left corner of the plot.
  • Or select "VeloVacuumAllpage" or "Pennings411412421422".
The sector valves VVFSF.33.1L8.X and VVGST.198.1R8.X, that seperate LHCb from LHC, can only be opened by AT-VAC if at least one of the ion pumps IP431/IP441 is on.

The state "Ready for Beam" is a combination of a several conditions, some of which can be overruled via a so-called "ignore"-action. This can only be done at the PLC-screen and is password protected. So if the vacuum system is NOT in the state "Ready for Beam" you cannot do much about it. The following information is there to help you to find the cause such that you can better judge what to do and/or who to call. Below it is assumed that no "ignore"-actions have been taken. "Ready for Beam" is defined as an AND of the following 11 conditions:

  • PS100=OK && PS200=OK (where OK means among other things PI101<1.0E-1 && PI201<1.0E-1 mbar) *
  • PI102<1.0E-1 && PI202<1.0E-1 mbar *
  • PS300=OK (where OK means GV302=closed && PI301<1.0E-3 && PE301<1.0E-6 mbar)
  • PS110=OK && PS210=OK (where OK means among other things PI111<1.0E-3 && PI211<1.0E-3 && PE111<1.0E-4 && PE211<1.0E-4 mbar)
  • PV301, PV302, PV303, PV304, PV305, PV306 and SV421 are closed
  • PI411<1.0E-3 && PI412<1.0E-3 mbar
  • PE411<1.0E-6 && PE412<1.0E-6 mbar
  • PI421<1.0E-3 && PI422<1.0E-3 mbar
  • PE421<1.0E-4 && PE412<1.0E-4 mbar
  • operating high voltage of ion getter pumps IP431 and IP441 > 2.5 kV
  • current drawn by ion getter pumps IP431 and IP441 < 1.0E-3 A
* note that limits for the PI102, PI202, PI101 and PI201 were changed from 1.0E-1 to 2.0E-1 mbar in July/August 2018!

The actual readings of gauges, valves and pumps can also (and partly better) be seen at the page named "Vacuum scheme" on the PLC-screen in rack C3B05 on platform C3. To display it, touch the screen once to get rid of the screensaver and then press the encircled button as shown in the figure below.


These can also be accessed in two ways:

  • from the VELO-consoles in the control room with the command XXXX
  • with SmartClient software running on "vepcmotion02w". Login to this machine as user "lhcb\velo_user". Start Mozilla Firefox and connect to and login to the screen of the vacuum-PLC. Or use one of the bookmarks.
Much more detailed information on the vacuum system can be found in EDMS-901535. See https://edms.cern.ch/document/901535/1

-- EddyJans - 2015-04-17

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PNGpng vac-overview.png manage 30.3 K 2015-05-27 - 13:30 KarolHENNESSY  
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Topic revision: r8 - 2018-08-25 - DanaBobulska

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