External Trigger System PAB To provide straight muon track efficient selection for TPC performance characterization Adjustable geometry for scanning different portions of the TPC. To possibly evolve into an external triggering/flagging system for operation in the n-beam line The easiest solution by plastic scintillator paddles in coincidence logic (and veto). More sophisticated options might be considered for operation in the n-beam line (if available)

S1 S2 S3 SA  ~ 10 deg Side View ToF ≈ 7-9 ns

101 cm 122 cm S1 S2 SA Dimensions: S1 = S3: 26 x27 cm 2 S2: 13 x 32 cm 2 S3 60 cm HV Settings: S1: V S2: V S3: V (SA: V) Discriminator Threshold: 300 mV (all) Front View

Signal Equalization By triple coincidence (S1.AND.S2.AND.S3) test set-up: Average signals from S1, S2 and S3 are equalized in Amplitude and Rate (taking into account the larger thickness and the smaller area of S2 w.r.t. S1 and S3) Standard Rates in final configuration: S1: 1000 counts in 45” S2 : 900 counts in 45” S3: 1050 counts in 45” SA: 1000 counts in 45”

1. All signal from S1, S2 and S3 are discriminated and NIM formed (25 ns width) 2. Logic: (S1.AND.S2).AND.S3 TTL signal (500 ns) is formed and sent to DAQ 3. This logic selects: a) Xing Muons b) Atm. Showers c) Accidental coincidences 4. To discard Atm. Showers: SA counter is added as VETO (presently Atm. Showers are only flagged and not VETOed, improvements/changes are due in the next few days) Present Rates: (S1.AND.S2).AND.S3: 1 evt/2min (≤ 50 % from Atm. Showers) Trigger Logic:

ToF 32+2 ns D 10 ns 1 ns 13 ns TTL to DAQ ToF S1 S2 S3 8 ns 20 ns 25 ns 200 ns 500 ns Timing AND 12 ns

External Trigger for -beam operation Three main topologies: 1.through-going  from beam -int. in the rock upstream  -int in LAr (good event to be selected) 3.Empty event: No interaction in coincidence with beam spill Four-fold logic with scint. paddles combined with beam spill trigger should efficiently tag -int in LAr ArgoNeuT