arXiv subjects

Stefan Welte

Publications and source records attributed to Stefan Welte.

4 recordsLinked to original sources

arXiv2025

First results of the Tritium Absorption InfraRed Spectroscopy (T2ApIR) experiment

The literature on experimentally verified material properties of tritium is sparse but information about this is crucial in fusion for pellet production (Magnetic Confined Fusion), target fueling (Inertial Confined Fusion), cryogenic distillation, as well as in astroparticle physics for neutrino experiments, and search for rare physics. To improve on this, the T$_2$ApIR experiment has been designed and built at the Tritium Laboratory Karlsruhe (TLK), and 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 phase, 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 in a measurement cell that allows optical access for infrared absorption spectroscopy, Raman spectroscopy and a polariscope setup, as well as temperature and pressure measurement.

physics.ins-det↗

arXiv2025

Commissioning of an experiment for thermodynamic and spectroscopic studies of hydrogen isotopologues at cryogenic conditions

To study thermodynamic properties and dynamic phase space behavior of hydrogen isotopologues (Q$_2$) at cryogenic temperatures and at high density, the Tritium Absorption InfraRed Spectroscopy 2 (T$_2$ApIR) experiment has been set up and commissioned at Tritium Laboratory Karlsruhe (TLK). In the frame of the experiment, Q$_2$ behavior in different phases, ortho/para states, temperatures (10 K - 300 K) and pressures (up to 2.5 bar a) will be investigated with optical methods, infrared and Raman spectroscopy. The facility consists of a fully tritium compatible cryostat, which includes an optical cell, ortho/para converter and windows for optical and spectroscopic studies. The cryostat can be cooled below the H$_2$ triple point by a two-stage cryocooler and contains openings in the cryogenic shielding for the optical access. The challenge of combining these scientific requirements in a design with high amounts of tritium (14 g), in a limited space, all while maintaining the TLK safety philosophy was solved by the presented design. The experiment is ready to be fully integrated into the TLK closed loop tritium infrastructure. This contribution reports a comprehensive overview of the commissioning phase of the experimental facility and the results of the first commissioning experiments, including cryogenic performance tests, commissioning experiments with non-radioactive gases, and tests of the analytical instruments.

cond-mat.stat-mech↗

arXiv2023

The Generation and Analysis of Tritium-substituted Methane

An unavoidable category of molecular species in large-scale tritium applications, such as nuclear fusion, are tritium-substituted hydrocarbons; these form by radiochemical reactions in the presence of (circulating) tritium and carbon (mainly from the steel of vessels and tubing). Tritiumsubstituted methane species, CQ$_4$ (with Q = H , D , T), are often the precursor for higher-order reaction chains, and thus are of particular interest. Here we describe the controlled production of CQ$_4$ carried out in the CAPER facility of the Tritium Laboratory Karlsruhe (TLK), exploiting catalytic reactions and species-enrichment via the CAPER-integral permeator. CQ4 was generated in substantial quantity (>1000 cm$^3$ at ~850 mbar, with CQ$_4$ - content of up to ~20 %). These samples were analyzed using laser Raman and mass spectrometry, to determine the relative isotopologue composition and to trace the generation of tritiated chain-hydrocarbons.

physics.chem-ph↗

arXiv2020

Neutral tritium gas reduction in the KATRIN differential pumping sections

The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the effective electron anti-neutrino mass with an unprecedented sensitivity of $0.2\,\mathrm{eV}/\mathrm{c}^2$, using $β$-electrons from tritium decay. The electrons are guided magnetically by a system of superconducting magnets through a vacuum beamline from the windowless gaseous tritium source through differential and cryogenic pumping sections to a high resolution spectrometer and a segmented silicon pin detector. At the same time tritium gas has to be prevented from entering the spectrometer. Therefore, the pumping sections have to reduce the tritium flow by more than 14 orders of magnitude. This paper describes the measurement of the reduction factor of the differential pumping section performed with high purity tritium gas during the first measurement campaigns of the KATRIN experiment. The reduction factor results are compared with previously performed simulations, as well as the stringent requirements of the KATRIN experiment.

physics.ins-det↗