分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： The knee phenomenon of the cosmic ray spectrum, which plays an important role in studying the acceleration mechanism of cosmic rays, is still an unsolved mystery. We try to reconcile the knee spectra measured by ARGO-YBJ and Tibet-III. A simple broken power-law model fails to explain the experimental data. Therefore a modified broken power-law model with non-linear acceleration effects is adopted, which can describe the sharp knee structure. This model predicts that heavy elements dominate at the knee.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
LIU Jin-Sheng
HUANG Jing
CHEN Ding
ZHZNG Ying
ZHAI Liu-Ming
CHEN Xu
HU Xiao-Bin
LIN Yu-Hui
ZHANG Xue-Yao
FENG Cun-Feng
JIA Huan-Yu
ZHOU Xun-Xiu
ANZENGLUOBU
CHEN Tian-Lu
LI Hai-Jin
LIU Mao-Yuan
YUAN Ai-Fang
摘要： Aiming at the observation of cosmic-ray chemical composition at the "knee" energy region, we have been developinga new type air-shower core detector (YAC, Yangbajing Air shower Core detector array) to be set up at Yangbajing (90.522∘ E, 30.102∘ N, 4300 m above sea level, atmospheric depth: 606 g/m2) in Tibet, China. YAC works together with the Tibet air-shower array (Tibet-III) and an underground water cherenkov muon detector array (MD) as a hybrid experiment. Each YAC detector unit consists of lead plates of 3.5 cm thick and a scintillation counter which detects the burst size induced by high energy particles in the air-shower cores. The burst size can be measured from 1 MIP (Minimum Ionization Particle) to 106 MIPs. The first phase of this experiment, named "YAC-I", consists of 16 YAC detectors each having the size 40 cm × 50 cm and distributing in a grid with an effective area of 10 m2. YAC-I is used to check hadronic interaction models. The second phase of the experiment, called "YAC-II", consists of 124 YAC detectors with coverage about 500 m2. The inner 100 detectors of 80 cm × 50 cm each are deployed in a 10 × 10 matrix from with a 1.9 m separation and the outer 24 detectors of 100 cm × 50 cm each are distributed around them to reject non-core events whose shower cores are far from the YAC-II array. YAC-II is used to study the primary cosmic-ray composition, in particular, to obtain the energy spectra of proton, helium and iron nuclei between 5×1013 eV and 1016 eV covering the "knee" and also being connected with direct observations at energies around 100 TeV. We present the design and performance of YAC-II in this paper.
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