ハロゲン化ガスの微量検出 (2)

抄録

Microcontent of various halide gases in air is detected by means of the following process. A mixture of air and halide gas is introduced into an ionization chamber in which a RaD source for ionization is installed and the decrease of ionization current, which corresponds to the content of the halide, is measured.
A method which resembles the above was adopted by Deisler et al. to the analysis of nonelectron-attaching gases by making use of the difference in specific ionization among gases. On the other hand, the combined processes of the electron attaching to the halide molecules and the recombination of the negative ions are found to be the main cause of the decrease of ionization current, and these processes are expressed by an equation. From this equation and experimental data, the electron attachment coefficient 7) for the next three electronegative gases is obtained, the value of which are 30cm^-1 TORR^-1 for SF₆, 0.2 for CCl₂F₂, 0.018 for air at E/P=0.12 v cm^-1 TORR^-1. These values are concluded to be appropriate as compared with the values obtained by other authors or reported in Part 1.
Various halide gases are compared with one another concerning their detection sensitivity: SF6 and Freon 11 were both found to be of very high sensitivity, better than 10^-5 TORR lit sec^-1. A brief explanation of a portable leak detector devised on the above principle is given.