IMPROVEMENT AND TRAIAL MANUFUCTURE ON A PORTABLE APPARATUS FOR CONTINUOUSLY MEASURING Rn-222 EXHALATION FROM GROUND

为了连续测量地表Rn-222的析出速率，研制了一套由60升圆柱形缓冲罐、三种过滤器和流通式电离室组成的测氡仪。测量的电离电流以模拟形式连续记录，然后使用预先导出的校准表脱机转换为Rn-222浓度。电离室为圆柱形抽吸冷凝器，内、外筒直径分别为0.05m和0.2m，一般长度为0.45m。外筒的电压保持在-1080伏。使用振动簧片静电计来测量电离电流。从所进行的基本实验中，获得了以下结果：(1)该装置能够连续记录测量数据，提供对Rn-222呼出速率的评估，并具有足够的实用精度。(2)即使在暴风雨天气，该装置也能稳定地运行，一旦找到一个稳定的公式--目前正在寻找--考虑风暴带来的收集器内外环境之间的差异，如地面条件、风速和气流速度--，评估精度的损害将被最小化。

For the purpose of continuously mesuring the rate of Rn-222 exhalation from the ground surface, an apparatus has been developed that consists of a radon collector a 60-litter cylindrical buffer tank, three kinds of filter and an ionization chamber of flow-through type. The measured ionization current is continuously recorded in analogical form, then converted off-line into Rn-222 concentration using a calibration table derived in advance. From the Rn-222 concentration, the exhalation rate is obtained by calculation.The ionization chamber is cylindrical aspiration condenser with inner and outer cylinders meauring respectively 0.05 m and 0.2 m diameter and 0.45 m in common length. The outer cylinder is maintained at a potential of -1080 volts. The vibrating reed electrometer is used to measure the ionization current.From the basic experiments performed, followings were obtained ;(1) The apparatus is capable of continuously recording measured data that provide an evaluation of Rn-222 exhalation rate with sufficient accuracy for all practical purpose.(2) The apparatus operates stably even in stormy weather, and impairment of evaluation accuracy can be expected to be minimized, once a sitable formula-now being sought- is found for taking account of the difference between collector interior and ambient exterior brought by the storm in respect of such factors as the ground conditions, wind and air flow speed.