1988 年 23 巻 3 号 p. 201-207
Ground level cosmic ray pulse height spectrum of a 7.5cm diameter spherical NaI (T1) scintillation detector was evaluated through stripping operation based on a pulse height spectrum measured on the sea and high precision response functions of the detector for U-series, Th-series and 40K. The exposure rate calculated from the determined cosmic ray pulse height spectrum was 0.21μR/h eq., which agreed well with that obtained from another method. The shape of the pulse height spectrum showed similarity to that measured at the altitude of 16, 000 ft, especially in the energy region of 0 to 3MeV. The principle of the adopted method is rather plain, however, the reliability of the spectrum is satisfactory. As the pulse height spectrum is a common information to any analytical method for environmental gamma ray using NaI (T1) scintillation detector, it is expected to be used for simple and precise separation of cosmic ray component involved in the enviromental pulse height spectrum.