The hydrophone detects vibrations in the light water looking for seismic events. The signal from the hydrophone connects into the SNO electronics via the hyrophone interface board (HIB) into the EXT2 trigger. The HIB cut searches for any event with an EXT2 trigger and then marks events in a time window around the event. Any event marked has the HIB bit and the discard bit of the RAA status word set. An accurate dead time introduced by this cut is reported during termination.
The two parameters for the HIB cut are in the RAAS 7 bank. These parameters are the time before the HIB event to mark, and the time after the HIB event to mark.
The HIB cut is called in the RAA by:
call($raa_hib_cut)
The results of the HIB cut should be sorted using the BITS dqf, for example in a programmable filter:
$enable_test 1 $define_test 1 $line_1 'hib bits ANAL+$KANAL_STATUS,$kraa_hib,1;'This filter will return positive for any marked event.