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Normal data output:

the output from the GTMerge program is a stream of coincidnece events:

HEADER:

CEvent.len
CEvent.lenclean
CEvent.lendirty
CEvent.lenbgo

CEvent.len tells how many events GTMerge thinks were in coincidence based on the coincidence time window was specified. All these words are 'unsigned short int' and serves as a header for the coincidence event. the lenclean, lendirty and lenbgo only make sense if there is GS data, but they are written out anyway. Then follows 'CEvent.len' structures of this format:

DATA:

typedef struct DGSEVENT
{
  short int               ehi;
  short int               id;
  unsigned short int      tpe, tid;
  unsigned short int      board_id;
  unsigned short int      chan_id;
  unsigned long long int  LEDts;
  unsigned long long int  CFDts;
  char                    flag;  
  short int               baseline;
  unsigned short int      traceLen;
  short int               trace[MAXTRACELEN];
}  DGSEVENT;

where only 'traceLen' of the 'trace' array is actually written to disk; so care should be taken to also only read that much of the trace in again.

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No coincidence mode


There is a switch in GTMerge, that will suppress the write out of the coincidence event header. If 'nocoinmode' is mentioned in the GTMerge chat file, only an infinite stream of DGSEVENT events are written out. The four header unsigned short int words are suppressed. The output suppression discussed below is still applied.

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output suppression:

Before an complete coincidence event is written to the output file, the program will calculate how many GE, FP and DSSD events are in coincidence. Using this structure (example):

minmul  2
minGE   0
minFP   3
minDSSD 0

you can suppress events that did not have those minimum number of counts in the coincidence event. Here minmul is the clean germanium count. In the above example we require three clean germaniums and three FP (focal plane) signal before we write the event out. This takes the place of some of the trigger conditions in the old analog Master Trigger module.