Updated 25 October, 2001
In the long term, we must establish a LockOut-TagOut_Verify procedure, because the consequences of an error may be very great. In the short term we have developed the following interim protocols.
The default mode of the detector is: HV OFF, tank sealed and light tight.
A local person is appointed Tank Czar, and is the sole person in charge of turning on HV and/or opening the tank. The name of the Tank Czar will be posted at the detector site. If the Tank Czar must be away from FNAL at all, a different person will be appointed temporary Tank Czar.
If work is to be done inside the tank that requires the light-tightness be compromised, the high voltage crates must be checked by the Tank Czar to be sure they are off and then unplugged and "tagged" with a sign stating that they are not to be turned on because the tank is open. No high voltage may be turned on until the tank is sealed and checked for light tightness and the signs removed by the Tank Czar.
No one will be allowed to work on the PA/QT racks with HV on or off except certain designated electronics experts. Others may be trained as needed. The names of the designated experts will be posted at the detector site. This means that no one else may install or remove HV cables, or fool around in any other way inside the PA/QT racks or crates at any time. Ever.
If work is to be done that requires the high voltage be turned on, then the tank must be sealed and checked for light tightness by the Tank Czar, and tagged with signs saying that the high voltage is ON. Tags must be placed on the top and bottom lid. Sealing the tank includes "locking" the lids; the top lid is locked at the hoist power switch, and the bottom lid is locked by a simple cable tie apparatus.
Before high voltage is turned on, the dark rates of two specific test PMT's must be checked. The test PMT's are 9-1B and 16-3SP. The first, 9-1B, is the veto tube closest to the bottom manhole; it's operating voltage is 2030V and measured dark rate is 9kHz. The second is a spare tube installed in the tophat; the operating voltage of 16-3SP is 1640V, and it's dark rate is 4-5 kHz.
If the light-seal of the tank has been breached since the last time high voltage was applied, then the light seal (at the lid and at the bottom manhole) must be visually inspected by the Tank Czar before the dark rates of the test PMT's are checked. In this case, the dark rates must be checked slowly, bringing up the voltage in steps of 100V and starting from 0V. If the light-seal has not been breached since the last time high voltage was applied, then it is sufficient to just check the test PMT dark rates.
The only allowed work on the pre-amp racks with HV on will be things like HV monitoring with safety HV probes and signal monitoring at points after the HV decoupling. Again, only electronics experts are allowed to do such work. At present, someone directly involved with HV work in progress should be present at the site as long as the HV is on. New protocols will be developed for long-term HV tests during the Detector Challenge.