Last night someone lowered the guard wire voltages because they noticed
that it was the guard wire rather than the sense wire which tripped.
This is exactly the wrong thing to do. The voltages in the wire
chamber are all relative to each other. Lowering the guard (or field)
wire voltages is like raising the sense wire voltages and just drives
it into noise. The WC voltages are all coupled.
When the guard or field wires trip there are two reasons: 1. there was
a large spark or the beam spray hit the chambers causing a huge amount
of current on these wires, or, 2. the power supply channel went out of
regulation usually caused by it being asked to sink rather than provide
current.
The correct thing to do when the field or guard wire trips is to go to
STBY and then go back to OPER. If the problem persists, lower the
sense wire HV while in OPER, SAVE that setting, and then go to STBY and
back to OPER.
If in doubt phone a WC expert.
Cheers,
Douglas
26-415 M.I.T.
Tel: +1 (617) 258-7199
77 Massachusetts Avenue Fax: +1 (617)
258-5440
Cambridge, MA 02139, USA E-mail:
hasell@mit.edu
This archive was generated by hypermail 2.1.2 : Mon Feb 24 2014 - 14:07:30 EST