First Experimental Results on the Tritium Viscosity in the Zero-Density Limit from 110 k to 300 k

The viscosity of tritium is an important property for fusion science and technology as well as fundamental research concerning tritium-based astroparticle physics experiments such as the KATRIN experiment. As of now, only theoretically calculated values with uncertainties of up to 7% are publicly available. No experimental results are found in literature, as there are not many laboratories with the license to handle the macroscopic amounts of tritium required to conduct experiments measuring material properties such as viscosity. The Tritium Laboratory Karlsruhe is unique in Europe, with a license to handle up to 40 g of tritium and around 30 g of tritium on site. With this contribution, we first present experimental values for the viscosity of tritium in the zero-density limit in a temperature range from 110 K to 300 K with a refined analysis. The measurement setup Cryogenic Viscosity Measurement Apparatus (Cryo-ViMA) is based on a spinning rotor gauge and was previously tested with helium, hydrogen, and deuterium in a temperature range from 200 K to 300 K. These results were reproduced with the final setup inside a glovebox, with a wider temperature range of 100 K to 300 K, before the measurement was conducted with tritium. The cooling is realized with a cold gas system utilizing liquid nitrogen. With this, temperatures down to 100 K can be reached, and there is a plan to upgrade the system for viscosity measurements at lower temperatures with the aim of reaching an accuracy of 2%. Through thermal cycling of the system, high resolution of the temperature dependency of the viscosity of tritium can be reached to test previous calculations.