First Measurements with the ENDA-INR Array of 16 Electron–Neutron Detectors

The ENDA Electron–Neutron Detector Array is under development in Tibet mountains as an integral part of a Large High-Altitude Air-Shower Observatory (LHAASO). A prototype of a single ENDA cluster consisting of 16 electron–neutron detectors has been constructed at the Moscow Institute for Nuclear Research (INR) and is used to study extensive air showers with energies above 1 PeV. A new procedure for data acquisition (DAQ) that relies on a 32-bit analog–digital converter (ADC) is used in these measurements. Calibration with radioactive sources shows that the DAQ procedure correctly selects neutron hits. Extensive air showers are detected in parallel with measuring variations of the thermal-neutron background.