Speaker
Description
The ICARUS Liquid Argon (LAr) Time Projection Chamber (TPC) detector is taking data on the Booster (BNB) and Main Injector (NuMI) neutrino beam lines at Fermilab with a trigger system based on the scintillation light (detected by PhotoMultiplier Tubes PMT) produced by charged particles on the time of proton beam extraction from the accelerators. The layout consists of National Instruments PXIe instrumentation to evaluate the presence of a certain number of PMT signals over a threshold (Majority level) in coincidence with the beam spill gates. The architecture and the deployment of the trigger system are presented.
Summary (500 words)
The ICARUS-T600 liquid argon (LAr) time projection chamber (TPC) detector is currently installed and taking data at shallow depth with the Booster (BNB) and Main Injector (NuMI) Neutrino Beams.
It plays the role of far detector in the Short Baseline Neutrino (SBN) program at Fermilab, searching for a possible LSND-like sterile neutrino signal at Δ𝑚2≈1eV2.
The detector consists of two identical modules, 19m x 3.6m x 3.9m, filled with 760t of ultra-pure liquid argon. Each module houses two TPCs separated by a semi-transparent shared cathode with a maximum drift distance of 1.5m. The TPCs (53,248 wires in total) are composed of three parallel readout wire planes with 3mm pitch, placed 3mm apart from each other and oriented at 0° and ±60° with respect to the horizontal direction.
The main ICARUS trigger system exploits the coincidence of the BNB and NuMI beams spills, 1.6µs and 9.6µs respectively, with the prompt scintillation light (produced by particle crossing the LAr) detected by PMTs as described in the attached figure.
The ICARUS trigger system provides a global trigger signal which activates 1.6ms and 26µs acquisition windows for TPC and PMT signal recording respectively.
The scintillation light is detected by 360 Hamamatsu R5912-MOD 8-inch PMTs installed behind the wire planes, with 90 PMTs per TPC.
Signals coming from the PMTs are read out by 24 CAEN V1730B digitizers. Each digitizer hosts 16 flash ADC channels, with 14-bit 500-MS/s sampling and 2Vpp input dynamic range. The digitizers generate trigger-request logical patterns via low voltage differential signal outputs (LVDS) which are activated by the presence of PMT pulses with amplitude exceeding a digitally programmed threshold. Each digitizer provides 8 LVDS lines that are fed into hardware modules that implement the trigger logic. The hardware setup consists of a NI-PXIe-1082 crate containing a NIPXIe-8840 real time controller, one PXIe SPEXI board by INCAA Computers and three NIPXIe-7820R Field-Programmable Gate Arrays (FPGAs). The SPEXI board generates signals based on the information of the proton extraction at BNB or NuMI through the White Rabbit (WR) network.
Two of the three FPGAs, one per cryostat, are dedicated to processing the LVDS signals from the PMT digitizer to generate PMT trigger primitives according to a Majority logic. Each trigger primitive is distributed both on the back-plane of the PXIe crate and to the PMT digitizer boards for PMT signal recording when in coincidence with the beam enable gate window. The third FPGA combines all signals present on the back-plane (beam gates and PMT trigger primitives) to produce the global trigger.
The global trigger is distributed both externally to other detector subsystems and via the backplane to the SPEXI board that records the timestamp.
The trigger system has been deployed, tested and successfully put into operation for physics, taking data with the BNB and NuMI beams and cosmic rays with the detector fully commissioned.
The performance of the trigger system will be described and discussed.
