RADIOISOTOPES

Crookes tube used in high schools generally emits leakage X-rays. The measurement method of the X-ray dose rate was presented by use of leaf electroscopes possessed in high schools. The open angle of the leaf of the electroscope changes with the electric potential of the electrode. The potential decreases by the collection of ions in the air produced by X-rays and the leaf closes. The ion density however accepts the effects of electric field nearby, surrounding wind and the polarity of electric charge of the electroscope. By taking the geometric mean value of the closing time of the leaf angle at positive electric charging and that at negative electric charging, it was able to obtain the reproducible relation between the dose rate measured with ionization chamber and the closing time. This relation called calibration line can be applicable to other similar commercial leaf electroscopes.