First Results of the Tritium Absorption InfraRed Spectroscopy (T ₂ ApIR) Experiment

The literature on the experimentally verified material properties of tritium is sparse, but information about this is crucial in fusion for pellet production (magnetic confinement fusion), target fueling (inertial confinement fusion), and cryogenic distillation, as well as in astroparticle physics for neutrino experiments and the search for rare physics.To improve on this, the T2ApIR (Tritium Absorption InfraRed Spectroscopy 2) experiment, designed and built at the Tritium Laboratory Karlsruhe, is in its scientific commissioning phase. The main focus of this experiment is to enable the investigation of the properties of all six hydrogen isotopologues and their mixtures in the gaseous, liquid, and solid phases, as well as the dynamics of their phase changes. In addition, mixtures with noble gases, such as xenon and neon, can be investigated.This is achieved using a cryogenic setup capable of reaching less than 10 K in a measurement cell that allows for optical access for infrared absorption spectroscopy, Raman spectroscopy, and a polariscope setup, as well as temperature and pressure measurements. Scientific commissioning measurements using the inactive hydrogen isotpologues (H2, HD, and D2) have demonstrated these analytical capabilities prior to tritium commissioning of the apparatus.