IMPROVEMENT AND CHARACTERIZATION OF SMALL CROSS-PIECE IONIZATION CHAMBERS AT THE TRITIUM LABORATORY KARLSRUHE

摘要

At the Tritium Laboratory Karlsruhe stainless steel cross-piece ionization chambers have been used to measure the activity concentration of tritiated gases in experiments and processes for more than 10 years. New chambers with an optimized design in terms of the effective chamber volume were produced. Furthermore, they were gold and copper plated to determine the influence of the coatings on the signal and on the memory effect. A new chamber of the old design was built for direct comparison of the signals. The chambers were characterized with different helium-tritium mixtures in 8 runs and the ionisation current as a function of the static gas pressure was measured. When comparing the three new chambers, the gold chamber always showed the highest current, followed by the copper chamber. After exposing the chambers to ～13,100 TBq/m~3, the memory effect was investigated by using a similar gas mixture of the earlier runs with ～l,500 TBq/m~3. The gold chamber showed the highest memory effect, the copper chamber the lowest. This paper describes the design and the testing procedure of the chambers. It presents the first experimental results on the chamber performance, on the memory effects as well as calibration curves.