There are several possible trigger sources. These are generally selected by the coincidence unit labelled TRIG.
The most common one is the muon trigger -- triggering off of the muon scintillator. The muon scintillator has two photomultiplier tubes (although it's a single scintillator), which are labelled M1 and M2. M12 is the linear sum of the signals from M1 + M2. The "muon trigger" is normally a coincidence of M1*M2*M12; the M12 signal defines the timing. The muon trigger then comes from the 4-fold coincidence labelled M.
The fourth input to the M coincidence is from a pulser, which can be used to simulate muon triggers; simply deselect the real photomultiplier inputs (M1, M2, M12) and select the TEST IN input. No change to the TRIG unit is required.
A concise recipe is available for switching from this pulser trigger to the real muon trigger.
It is also possible to trigger off of the upstream positron counters (PU), or the downstream positron counters (DS). Each of these triggers is just the coincidence of all appropriate photomultiplier signals; these coincidences are already set up in the logic, so changing to these triggers requires, for example, deselecting the M input to TRIG and selecting the PU or DS signal.
Last modified 02.06.19 by Robert MacDonald.
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