Commissioning and detailed results of KATRIN inner loop tritium processing system at Tritium Laboratory Karlsruhe

• We have achieved a high stability gas injection (<20 sccm).
• The stabilisation of the gas flow has been achieved according to Ohm's law.
• The setup is necessary for the closed tritium loop operation of the neutrino experiment KATRIN.
• The achieved results enable the operation of the KATRIN tritium source (WGTS) as required by the experiment.

The Karlsruhe Tritium Neutrino (KATRIN) experiment will investigate the tritium β-decay close to the energetic endpoint with unprecedented precision, to determine the effective mass of the electron antineutrino. Therefore it has stringent requirements on the stability of the tritium source. The tritium loop system has the task to provide the stabilized flow rate of tritium gas into the KATRIN tritium source with a throughput of 40 g/day and a tritium purity >95%. In this paper the physical setup of the injection system will be described, followed by the description of inactive commissioning measurements. Their analysis shows that the stringent requirements will be perfectly met by the newly designed injection system.