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Operating the VELO Vacuum System while being under a neon atmosphere

  • In the following DP refers to the differential pressure between beam and detector volume: DP = p_beam - p_det.
  • When cooling down from room temperature to +10 deg. C with the baseplat hating "ON", DP will increase by approximately 3 mbar.
  • In the following the neon Gas Injection System is supposed to be non-active.
  • In the following a correct reading of the baratron DP is assumed. If not, consult an expert because it then has to be calibrated via a special procedure. This might generate the blowing off of all the CO2 that is inside the cooling system of the VELO !!
  • Make sure the PVSS-project "VEDCS_VacMot" is running under "velo_user" on "vedcs02w". If not, start it and start via "Vision" the panel G:\velo\pvss\VELO_VacuumMotion\panels\VeloVacuum_UI_Main.pnl

Create good starting conditions:

  • If -4.5 < DP < -2.0 mbar, you are lucky and can continue with the paragraph "Operating the vacuum PLC for cooling activities ....". If not, you first have to create a good starting condition, i.e. a good value of DP. This can be done by moving the detector halves. So perform the following actions.
  • bypass the vacuum interlock that prevents moving the detectors. Push the following marked buttons on the PLC screen. If you are on a different page press the "Home"-button (bottom-left) or "Vacuum control"-button to get there.

  • screenshot.4.jpg

  • screenshot.5.jpg
  • now the 4 lights that are encircled should be green, indicating you can move the VELO-detectors.
  • Pull out the red mushroom button on the motion system in motion rack C3B03 at 1m20 from the floor.
  • go to the "motion control" screen. Beware of the fact that a higher value for both X-LEFT and X-RIGHT corresponds to more to the outside !! Move alternatingly the VELO-halves outwards in steps of 1 mm. (At AP=850 mbar moving 1 mm outwards corresponds to an increase of DP of 0.6 mbar.) Wait after every step until the pressure is stabilized. To move a detector half, touch the corresponding setpoint, type a new value, type return, make sure you did the right thing, press the "MOVE HORIZONTALLY (X)" button and watch carefully what happens with: position, potmeter readings, DP411, PV301 ... 306 (which should stay closed, which means red ??).

  • screenshot.2.jpg
  • When DP has reached a value between -4.5 and -2.0 mbar: press the red mushroom button on the motion system in motion rack C3B03 (to inhibit movement of the detectors) and remove the bypass (in other words reactivate) on "inhibit to motion".

  • Now you can from the neon point of view start the warm cooling.

-- EddyJans - 16 Apr 2008

Topic attachments
I Attachment History Action Size Date Who Comment
JPEGjpg screenshot.2.jpg r1 manage 82.5 K 2008-04-17 - 18:34 EddyJans  
JPEGjpg screenshot.3.jpg r1 manage 114.1 K 2008-04-17 - 18:26 EddyJans  
JPEGjpg screenshot.4.jpg r1 manage 72.6 K 2008-04-16 - 17:26 EddyJans vacuummainpage
JPEGjpg screenshot.5.jpg r1 manage 66.9 K 2008-04-16 - 17:29 EddyJans bypassinterlock
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Topic revision: r3 - 2008-04-17 - EddyJans
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