The Burst Cut

The burst cut is called in the RAA by:

   call($raa_burst_cut)

The burst cut will discard any group of events that have a threshold number within a set time window. The group will continue to increase in size until the threshold is no longer passed. An extra amount of dead time can also be added around a group if desired. Up to ten different burst cuts can be used at the same time by this subprocessor. The burst cut status word is used so that if bit i is set then the event failed cut i. Bit zero will be set if the event is the first event of a burst and spectial treatment of first events is enabled. In this case bit i is not set for first events. Dead time can also be set at the start and end of files to avoid edge effects. All these settings are controlled in the RAAS 6 titles bank. This bank must be set correctly, with the correct number of burst cuts specified.

Each burst cut has six parameters:

• The threshold number of events in a burst.

• The time window for the burst.

• The dead time around a burst.

• A switch to set the required masks for the burst. This is a bit mask applied to the burst cut status word, and can be used to ignore events already marked in a burst. The one exception is bit0 which is used to control the responce towards events discarded by other subprocessors.

• A switch to tell the burst cut to mark the first event of a burst as such. This is useful as a perfectly good event can cause retriggers, and would then be cut by the burst cut. If a first event is marked, the first bit of the burst cut status word is set, as well as the bit for the cut it failed. If this switch is set the first event is also not marked as being in a burst for the purpose of further burst cuts.

• The nhits threshold for an event to count towards a burst.

• A switch to ignore events with NCD data.

• A switch to ignore events without NCD data.

• The shaper ADC threshold for events to count towards a burst.

As PulseGT can interfere with the burst cut these events are not counted when the time window is scanned over the data, but will be marked if events occur within a burst. Removal of any other events by other subprocessors or filters will interfere with the operation of the burst cut, and should be avoided.

The burst cut can also be used to look for subrun boundries. An ammount of time can be set to be marked at the start and end of files. Events in this period will have bit 31 of the burst cut status word set. this can be fed back into the bitmask control used for individual burst cuts.

During the termination phase the subprocessor will report the statistics for each burst cut individually and for the process as a whole. The final report will also give a accurate dead time calculation for each burst cut.