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 Drift Chamber High Voltage Trip Recovery Procedure
status: 7/31/2001

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* Follow the steps described under ``Case A'' and ``Case B''.
* Call Drift Chamber expert in case of problems.
* DO NOT OPERATE THE BUTTON ``UPDATE CHANNEL CONFIGURATION''. 
   THIS FEATURE IS FOR DRIFT CHAMBER EXPERTS ONLY.

•  Case A --  Trip(s) ONLY on Cathode channel(s), i.e. channel names ending on "_C":

 
• Click on the "disable" button of the tripped channel(s). Wait until the request light has changed from green to yellow AND the status shows "0".
• Then click on the "enable" button. Check the request light changing to green, the status changing to "1" and that voltages are raising.
• Repeat this procedure several times in case of problems.

 

 

•  Case B -- Trip(s) on Potential, Gate and Backdrift channels, eventually together with trip(s) on Cathode channel(s):
 
Follow a three-step trip recovery procedure. Click on the three buttons located at the bottom of the Drift Chamber voltage/current page concerned. Important: Prior to performing operations, open also the twin page of a particular group of keystones. Then perform each operation in parallel in both pages: First step 1 in both pages, then step 2 in both pages, then step 3 in both pages. Twin pages are e.g.:
* DC_W_S_KEYSTONES_0-7_X2
* DC_W_S_KEYSTONES_0-7_UV2
 
• step 1:  Ramp Down;

Cathodes (_C) and Bulk Supplies (_PBS,_GBS,_BBS) will ramp down. The request lights change from green to yellow. Wait for completion of the ramp-down. The status for of every channel with yellow light must be "0". The measured voltages must be low, i.e. of the order of absolut 20 V or less.
Repeat step 1 several times in case of problems.
If all is ok in both pages, proceed with step 2.
 
• step 2:  Reset;

First, the channels of type _P,_G,_B will disable and the alarm states will cancel. The channels will enable again after a short delay.
IMPORTANT: Make sure that every green channel shows status "1".
Repeat step 2 in case of problems. Call expert if a problem persists.
If all is ok in both pages, proceed with step 3.
 
• step 3:  Ramp Up;

Bulk supplies (_PBS,_GBS,_BBS) will enable first, Cathodes will follow shortly after. Check that all green channels show status "1" and voltages are raising everywhere.