Calibration of a NaI(Tl) airborne spectrometer for 137Cs simulated area sources

By using numerical integration method, two limited (radius as 15 m) and a infinite 137 Cs uniform area sources are simulated with tens of 137Cs point sources. A NaI(Tl) airborne spectrometer set in Yun-5 airplane is calibrated for the simulated area sources. The mean of calibration factors of the spectrometer is 2.98 x 10-2m2 for two limited sources. The calibration factor of the spectrometer is 3.77 x 10-2 m2 for the infinite source. The uncertainty of the calibration factors is estimated, and it is less than 20%. The calibration factors are also calculated by angle response function on the conditions. The results of measurement and calculation are of agreement within 10%