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By accurate measurement of components and energy spectrum in the knee region, problem of origin of cosmic ray can be solved. In one extensive air shower (EAS), high energy hadrons, which constitute the EAS skeleton as G.T. Zatsepin called it, carry important information for multi-parameter correlation studies. The nuclear reaction between hadrons and matter in the surrounding environment produces a large number of evaporation neutrons, moderating to thermal neutrons. At the beginning of the 21th century, a new technology, electron–neutron detector (EN-detector) was designed at Institute for Nuclear Research of Russian Academy of Science (INR RAS), and the PRImary Spectrum Measurement Array (PRISMA) project was proposed to reinforce array capability of cosmic ray composition separation and then improve measurement accuracy of cosmic ray components and energy spectrum. Besides, EN-detectors can be used for continuous environmental thermal neutron flux monitoring and its variation study is needed not only for EAS experiment background estimation but also for geophysical applications (e.g., earthquakes, thunderstorms, radioactive aerosol control, etc.) and solar activity study (e.g., solar flares, Forbush effects, etc.). Under the Chinese–Russian cooperation, we put forward to build so called EN-Detector Array (ENDA) at high altitude in China. At YangBaJing Hybrid Array (YBJHA, 4300 m a.s.l.) and at Large High Altitude Air Shower Observatory (LHAASO, 4410 m a.s.l.), two clusters of ENDA were built individually and all have obtained coincident events with the local arrays. In the near future, we plan to extend ENDA to ENDA-64 with array area of 1000 m inside LHAASO to study the knee region of the light components (H and He). After it, ENDA will be extended up to 400 detectors with array area of 10 000 m to extend the energy range up to 300 PeV. [ABSTRACT FROM AUTHOR]

The measurement of thermal neutrons generated by cosmic ray extensive air showers (EAS) on the Earth's surface provides a new method for studying the composition and energy of cosmic rays with energy in the so-called "knee" region. Given the success of the PRISMA-YBJ array, a new type of thermal neutron detector array was installed at the high-altitude cosmic ray observatory in Yangbajing, Tibet. The array consists of 16 EN-detectors and utilizes a new type scintillator based on a compound alloy of ZnS(Ag) and B2O3 with natural boron. This report describes the deployment of the detector array and its operational results. [ABSTRACT FROM AUTHOR]