A study on structure of air shower by iron open sandwich experiment

For the direct measurement of longitudinal development of air shower, it has been proposed to observe the shower development in absorption layers installed on the ground. In this study, absorption layers of iron are placed on part of the scintilation counters, like 'open sandwich', and each set of counters with or without absorption layers is used as an independent array. The aim of the present work is to simulate the shower development at Norikura (2770 m, 735 g/cm2) on the basis of data obtained at Akino (900 m, 920 g/cm2). Two models are employed to represent the shower development. Procedures are presented to determine the energy of primary cosmic rays and altitude of shower generation, to estimate the average energy of shower particles and to simulate the structure of shower at Norikura. Air shower data obtained are analyzed according to these procedures. It is shown that the energy of primary rays and generation altitude of air shower determined by the electromagnetic cascade theory agree with those determined by conventional methods. As the average energy of shower particles, values of 110 - 140 MeV are obtained which also agree with those previously reported. Correlation between the average energy and age parameters is determined. The simulation for Norikura on the basis of Akino data shows that the average energy of air shower particles at the Norikura altitude is in the range of 200 - 230 MeV. These results indicate that the simulation of air shower of Norikura is satisfactorily carried out by the method proposed. (Nogami, K.)