Timing logic

The TOF trigger timing logic consists of four stages shown in Fig. . The nominal timing discriminator is gated with a high level discriminator set at approximately MIP (minimum ionizing particle). This is repeated for both the forward and backward PMTs. Signals from the forward and backward PMTs are then required to be within ns coincidence window by the mean timer circuit. This removes random noise hits in scintillators or PMTs.

Next, the mean time signal is required to be in coincidence with a hit in the corresponding TSC counter. To allow for track curvature, the coincidence is taken between one TSC and four TOF counters, which removes background hits caused by photons converted in the TOF scintillators. The combination of one TSC and four TOF scintillators constitutes one trigger segment.

The above logic is repeated 64 times to form a 64-bit hit pattern. Finally, the TOF trigger timing signal is formed by taking OR of all 64 segments. Thus the first arriving segment hit determines the event timing.

Figure: TOF trigger timing logic.