The Study Of Properties Of Air Shower Cores Using Core Detector

There has been always concerned since the knee of spectrum of cosmic rays was covered. Nowadays, there has a knee structure of spectrum of cosmic rays by all of the air shower experiment. Although, the knee structure of spectrum has been confirmed, the debate on significant inconsistencies about conclusion of position and shape of cosmic-ray spectra at the knee energy region, and nucleus composition of cosmic rays at the knee energy region especially. Generally, the knee energy region of primary cosmic rays refers to1015eV～1016eV region. Measurement of knee energy region cosmic-ray by ground experiments basically. There are significant inconsistencies of the all-particle spectrum of cosmic rays among different experiments. There has a17%error on reconstruction of energy among different experiments, but the all particles spectra are basic consistent in a permissible error range among different experiments. But, there are obvious differences between different measurements of different nuclei spectra at the knee energy region, even between measurements with different experimental devices by an experiment. Therefore, the composition of primary cosmic rays at knee energy region is still a hot topic of debate in the experimental cosmic-ray physics research.The composition of cosmic rays at the knee region is one of the important issues in research of cosmic-ray, it is related to the origin and acceleration and propagation of the high-energy cosmic-ray. Therefore, we proposed the Yangbajing Air-shower Core (YAC) detector array program.We have operated the500m’Yangbajing air-shower core (YAC-II) detector array near the center of the Tibet air-shower array (Tibet-III) to study the cosmic-ray chemical composition at the knee energy region since August,2011. YAC-II array consists of124YAC detector units. Each unit of YAC-II consists of a lead layer of3.5cm thick and a scintillation counter which detects the burst size induced by high energy electromagnetic component in the air-shower cores. Each scintillator has the size80cm x50cm x1cm.60WLSFs (Wave Length Shifting Fiber) are installed inside the scintillator, a high-gain PMT and a low-gain PMT are coupled with it. The burst size can be measured from1MIP (Minimum Ionization Particles) to106MIPs. In this paper, the details of the hybrid experiment and the processes of the data reconstruction are described.Finally, this work got some properties of the air-shower cores at the knee energy region of cosmic rays. And, evaluation is given for the YAC-II detector array performance and operation of the experiment. This work proved that the experiment is a normal operation and its hardware is successful and the YAC-II detector array experiment can be successfully achieved its physical objectives.