JINR test stands
NOvA Base elements
APD, FEB and scintillator
The main goal of the NOvA experiment is to study oscillation parameters in the neutrino and antineutrino beams: measurements of the mass hierarchy and CP-violation phase in the lepton sector. Two identical highly-segmented detectors based on PVC-tubes filled with a liquid scintillator to detect signals from muon and electron neutrinos were built. Masses of each are 300 and 14000 tons. Avalanche PhotoDiode is used to measure signal response. Total amount of these devices in the large Far Detector is 344064. A NOvA cell is a tube filled with liquid scintillator. Light from the scintillator is captured by the fibers and is transmitted to the APD. Fibers from 32 cells are grouped on one APD board.
The NuMI beam at Fermilab creates a "spill" of neutrinos every 1.3 seconds. Each spill lasts for only 10 millionths of a second: and careful timing (with the aid of the GPS system) is used so that the computers collecting the NOvA data know exactly in which 10 microseconds this happened. Looking only at the slice of time during which the beam fired now shows only two things: a cosmic ray muon on the left side of the detector, and the interesting spray to the right. That is the result of a neutrino from Fermilab hitting an atom in the NOvA detector, producing a spray of subatomic particles that cause the scintillator they pass to give off flashes of light. The scale on the bottom right is colour-coded to show how much light each cell saw: from blue (not a lot) to red (a thousand times the minimum).
This q is the number of the ADC counts. Signals that we are looking for the main NOvA scientific goals are not really huge (q < 500).
It is crucial to measure various parameters of the electronics and scintillator for better understanding of different features and further integration of the results into DAQ, analysis etc. For these purposes we have two test stands for the NOvA experiment at JINR: