A method of measuring attachment coefficients in weakly attaching gas mixtures

The neutron sensitive pulse fission ionization chambers which are often used to measure power in nuclear reactors operate by electron collection and their performance depends on minimizing electron attachment. They are filled with selected gases but specifications for impurities and for outgassing from walls are necessary. There is therefore considerable practical, as well as fundamental interest, in determining attachment coefficients in filling gases and their mixtures with common electro-negative gases such as oxygen and carbon-dioxide. In this paper a pulsed drift-tube designed to determine attachment coefficients under these conditions is described. In order to calibrate the apparatus, an initial gas-filling of oxygen was used and some of the preliminary results are presented. (author)