System:Møller Polarimeter

In preparation for a planned power outage affecting the Møller Polarimeter, operators should:

• Ramp down Q1 and turn off power supply
• Ramp down Q2 and turn off power supply
• Put solenoid in non-persistent mode, ramp down, turn off.
• Move all collimators to RETRACTED position.
• Move target ladder to RETRACTED position.
• Depending upon expected duration of power outage:
  • more than 5 minutes: Close (0%) LN2 and LHe supply (JT) valves. Close cold return valve. Open (100%) warm return valve.

  • 5 minutes or less: no change to cryo

Response to an unplanned power failure:

• While power is off there is no control nor is there anything to be controlled. (i.e. there is nothing you can do).

• Be aware that if the solenoid was ON and in PERSISTENT mode, it will remain on until the coils warm up from lack of helium. At that point the magnet will quench, dumping its energy in the leads and the power supply shunt resistor.

• Personnel entering the beam tunnel must be aware that the solenoid field may still be on and that the solenoid is likely to quench.

Recovery from a power failure (ONLY IF THE Møller WAS ON)

• (Controls IOCs will normally come up on their own as soon as power and network communications are available)

• Re-start vacuum pumps (two of) under the beamline near the polarimeter. (Also restart other vacuum pumps in the hall related to cryo transfer lines vacuum.)

• Contact a Møller expert and determine the cryogenic status and how to proceed. If no expert is available, use the Møller cryo MEDM screen to close LN2 and LHe supply JT valves (if not already closed) [EV91017 and EV91018], close LHe Cold-Return JT valve [EV91019], and open warm return ball valve [EV91001]. This will turn off the cryogen supplies to the Møller solenoid.

  NOTE: if the solenoid is still energized (persistent mode) it is preferable to keep it cold if possible, in order to avoid a quench.

• Using the Møller Collimators MEDM screen, execute "GO HOME" on the target ladder. When the target is HOME execute "GO HOME" on the collimators. Wait for completion, then send both the target and the collimators to the RETRACT position unless directed otherwise by a Møller expert.

• Enter Hall-C and inspect the cooling water flow gauges: make certain that cooling water is flowing.

• In the hall, locate the Møller controls rack (HC01Z03). Press "START" on the Q1 power supply. Behind you is the Q2 power supply. An authorized person should reset it, clear any faults, and return the supply to REMOTE mode.

• Notify MCC that the Hall has undergone an interruption of power and remind them that they must restore the maximum voltage parameter (known as ``VSET'') on the Møller Q1 power supply MEDM screen.