Cosmic Ray Study in Nishina Laboratory

Abstract

The cosmic ray research in Japan was initiated by Dr. Yoshio Nishina in 1931. In the summer of that year, he was nominated chief of a new laboratory (Nishina Laboratory) of The Institute of Physical and Chemical Research (I.P.C.R.). There, R. Sagane soon started to make Geiger-Müller counters. The first counter was made of a copper tube 5 cm in length and 2 cm in diameter. Both ends of the tube were shielded by ebonite plugs, and a steel wire was stretched between the plugs as a central electrode. This counter was of the shape that two “Spitzen Zahler”s were connected facing each other. Fortunately the discharge characteristics of this counter showed a plateau as large as 50 volts, and it was primarily used to measure the intensity of radiation in the laboratory, When the center of a typhoon passsed through Tokyo area in the fall of this year, it was found that the counting rate varied with decreasing atmospheric pressure, and later returned to the normal rate when the typhoon had gone. Apparently there was a significant correlation between the counting rate and the atmospheric pressure.