Matsumoto S, Kobayashi H
Radioisotopes. 1983 Sep;32(9):399-403. doi: 10.3769/radioisotopes.32.9_399.
Changes in air density due to humidity were measured by a scintillation detector with alpha-particles. The distance between the scintillator and an alpha-ray source of 241 Am, 3.7 MBq (100 microCi), was fixed at 25 mm which was a little shorter than the range of alpha-particles from the source. The measured absolute humidities were in a range of 7.9 g/m3 to 52.2 g/m3 at temperatures of 35 degrees C and 45 degrees C and under atmospheric pressure. The counting rate of alpha-particles in an absolute humidity of 31.7 g/m3 (80% in relative humidity) at 35 degrees C increased 28% compared with that in dry air. From experimental results and theoretical calculation, the counting rate difference between humid air and dry air was shown to be almost proportional to the absolute humidity in air. The absolute humidity can be measured with an accuracy of +/- 3 g/m3, that is +/- 5% in relative humidity at 45 degrees C.
利用带有α粒子的闪烁探测器测量了湿度引起的空气密度变化。闪烁体与活度为3.7 MBq（100微居里）的241 Amα射线源之间的距离固定为25毫米，略短于源发射的α粒子射程。在35℃和45℃以及大气压下，测得的绝对湿度范围为7.9 g/m³至52.2 g/m³。35℃时，绝对湿度为31.7 g/m³（相对湿度80%）时α粒子的计数率比干燥空气中增加了28%。从实验结果和理论计算来看，潮湿空气和干燥空气之间的计数率差异几乎与空气中的绝对湿度成正比。绝对湿度测量精度可达±3 g/m³，即在45℃时相对湿度为±5%。
