On the component of cosmic ray particles

Study on the life of cosmic ray in the galaxy has been developed recently, and the energy spectra of nuclei in cosmic ray were observed. The energy spectra of heavy nuclei such as iron were different from those of light nuclei. The abundance of iron increases with energy. This phenomenon suggests that the light nuclei such as Li, Be and B produced by spallation reaction are expected to decrease with increasing energy, and give information on the life of cosmic ray. Direct estimation of the life can be made by the observation of the abundance of finite life isotopes in cosmic ray. An example is the observation of Be10 with life of 3.7 x 106 years. The nuclei which are heavier than iron are observed in cosmic-ray, though the amount is small. Observation of the energy spectra of primary electrons in cosmic ray will give the life of the electrons in the galaxy. The measurement mentioned above has been made with balloons. In Japan, emulsion chambers were used for the observation, and this method may be useful for future study on high energy. Methods of observation in Japan are described in this paper. (Kato, T.)