Multiplicity Event Triggers

Since the Multiplicity trigger also uses a CFD I modeled its behaviorusing the same techniques as that of the single Pixel CFD. I built up thesummed waveform from the logic pulses from the PCFD's using a constant logic pulse shape(specified below) to form the summed pulse. Again I used the various CFD parameters asset in the experiment in the model. Figure 2a shows the result for a particulartrigger. Again the trigger time is usually set by the time by when the summedlogic pulse reaches the MULTFRAC fraction (see below, set presently to 33% I think) of the total pulse height. Usually! I did find a funny behavior (see Figure 2b )which occurs when a PCFD trigger, probably due to noise, triggers more then MULTDELAY (typically 7.5 ns) before the main shower pulse., In that case thetrigger occurs much earlier ( 7.5 ns) then it should. One way to prevent thiskind of trigger is to increase the MULTFRAC to 66%. See Figure 2c ). That'sa recommendation I now make.

• PCFD Nim Logic output pulse rise/fall time: 2 ns
• PCFD Nim Logic output pulse width: 10 ns
• Multiplicity CFD Fraction (MULTFRAC): 33% (or 66%)
• Multiplicity CFD Delay (MULTDELAY): 7.5 ns
• Multiplicity CFD threshold: 1.5 of logic pulse (2 fold).