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BaBar Drift Chamber

Gas System

  Documentation of the restart of the gas system

(updated Oct 3rd 2003)

  This state machine is used to restart the gas system either automatically after
an alarm, or manually by clicking on an EPICS panel.

  The control of this state machine can be accessed from DCH -> Gas System -> Experts -> Control Panels -> Restart of Gas System.
  The state machine has 2 modes: automatic or manual. These modes can be changed (by super-user) by clicking on "Set Mode" on the restart panel. During manual mode, the super-user has explicitely to click on the button "Push to restart" to restart the gas system (he has also the possibility to cancel the restart at any time with a special button).
  During automatic mode, the state machine detects an alarm and tries to restart itself without human intervention (only one try).
  Notice that mails are always sent to experts in case of alarm, no matter if the state machine is running or not!
  In both mode, this state machine can be used to restart (with an explicit click of the user) the system after a shutdown, or in all other situation (not only after an alarm!).

  During a restart, some informations are available on the restart panel. There is a progress bar showing the progression of the state machine. There is also a status bar with 3 different messages: "Trying to restart...", "Restart completed" and "Unable to restart. Call experts".
  A mail is also sent to experts with the result of the operation.

  The alarm handler was modified to precise to the shifter where to look. In case of alarm, he is advised to click on the "P" box of the restart channel to see the progression of the state machine.
  The status of the restart is also available on the shifter panel of the gas system.
  Here is the principle of the state machine, which is made of 2 layers.
  First layer (when someone push the "restart button"):
  1) - if we are in alarm, go to rest mode and go to 2)
      - if we aren't in alarm, go to rest mode and go to 3)
      - if we are in running mode, do nothing
      - if the isobutane concentration is lower than 15%, do nothing (just in case someone tries to restart the system during the summer shutdown for example)
  2) wait 60 sec, and if there is no more alarm, then go to 3), otherwise abort
  3) check the chamber pressure, if it's below 4.3 mbar then go to VME mode and
      go to 4), otherwise go to 6)  
  4) open all valves, but valves 5 and 6, which has for effect to "inflate"
      the chamber
  5) check the pressure. If the pressure is above 4.3 mbar, go to rest mode and
       go to 6). If the pressure is still below 4.3 after 6 minutes, then the state
       machine aborts
  6) go in run mode. As the pressure in the chamber is high, the motors
      of the circulation loop will turn quickly, thus giving a sufficient
      pression in the circulation loop, avoiding another alarm
  7) wait 60 sec to check if there is alarms. If not, the restart was successful

  Between each change of mode (e.g. rest mode -> VME mode), there is a waiting delay to ensure that the system has changed its mode (15 sec as it can be long to go from alarm mode to rest mode).
  At each step, the state machine checks if there is an alarm or if the user pushed the "cancel" button.

  Second layer of the state machine (when automatic mode is set):
  1) - if there is an alarm DURING RUNNING MODE and the number of try is
       equal to 0, then push "programmatically" the "restart" button (so that
       the first layer of the state machine is launched). Set the number
       of try to 1, and go to 2)
     - if there is no more alarm after 5 minutes of running mode, then set
       the number of try to 0
  2) wait for the completion of the first layer and go to 1). After 12 minutes,
       if nothing happens, abort, and go to 1)  

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