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Measurement of Nuclear Composition of Primary Cosmic Rays

初级宇宙线核成分的测量

基本信息

批准号：
08041101
负责人：
KAKIMOTO Fumio
金额：
$ 6.85万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08041101/
关键词：
Cosmic Rays Air Shower Nuclear Composition Knee Region Air Cherenkov Light Longitudinal Development Arrival Time Distribution Origins of Cosmic Rays 加速源

项目摘要

The nuclear composition of primary cosmic rays is clue information for the investigation of the cosmic ray origin. In the energy range above 10^<14>eV,however, no direct observation can be done because of their low intensities. Observed primary energy spectra show the well known bending around 10^<15>eV,the knee of the spectrum, and this bending is thought to be related to some changes of acceleration mechanism of primary cosmic rays. In the present research, we have measured the arrival time distributions of air Cherenkov light associated with air showers at Mt, Chacaltaya in Bolivia. The primary nuclear composition reflects deeply on the longitudinal development of corresponding primary cosmic rays especially at upper atmospheric depth, and then on the arrival time distribution of air Cherenkov light associated with corresponding air showers. On the basis of a result of our Monte-Carlo simulation, we chose the rise time of integrated Cherenkov pulses as a parameter which characterizes the arrival time distribution. The observed rise times are classified according to air shower sizes and incident zenith, angles of their associated air showers. Then the distribution of classified rise times are compared with those calculated with a Monte-Carlo technique. The preliminary result on the nuclear composition at the knee region is as followings :(1) the average atomic number of primary cosmic rays is 9 to 15 below 10^<15.5>eV,and gradually increases with primary energy,(2) main component is He and CNO group at 10^<15>eV,and Ne-Fe group above 10^<15.5>eV,In anyway, our result is inconsistent with such models of cosmic ray origin that protons are dominant in the primary cosmic rays above the knee region. This result suggests that super nova explosions of massive stars such as Wolf-Rayt stars are favorable for the origin.

原始宇宙线的核成分是研究宇宙线起源的线索信息。然而，在10^ eV以上的能量范围内<14>，由于其强度低，无法直接观察。观测到的一次能谱在10^ eV附近出现了弯曲<15>，这被认为与一次宇宙线加速机制的某些变化有关。在目前的研究中，我们已经测量了空气切伦科夫光的到达时间分布与空气阵雨在玻利维亚山，Chacaltaya。初级核成分深刻地反映了相应的初级宇宙线的纵向发展，特别是在高层大气深度，然后在相应的空气簇射相关的空气切伦科夫光的到达时间分布。在蒙特-卡罗模拟结果的基础上，我们选择了积分切伦科夫脉冲的上升时间作为表征到达时间分布的参数。观测到的上升时间是根据空气簇射的大小和入射天顶，其相关的空气簇射的角度进行分类。然后将分类后的上升时间分布与用蒙特-卡罗方法计算的上升时间分布进行了比较。膝区核成分的初步结果是：（1）在10^ eV以下，初级宇宙线的平均原子序数为9 ~ 15<15.5>，随初级能量的增加，原子序数逐渐增加;（2）在10 ^ eV以上，主要成分为He和CNO基<15>，而在10^ eV以上，主要成分为Ne-Fe基<15.5>。这一结果表明，大质量恒星如沃尔夫-雷特星的超新星爆炸有利于起源。