Hydrogen contaminations in liquid helium

• Applicant: Professor Dr. Christoph Haberstroh
• Subject Area: Technical Thermodynamics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 511871157

The proposed study is about new problems and phenomena reported from liquid helium users worldwide when working with pumped liquid helium as cooling fluid. Here a clogging of small passages is observed. In earlier inspection hydrogen contaminations could be identified as cause. It was found that the observed clogging can be effected by extreme small hydrogen concentrations in the ppb range. However, details and parameters like solubility limits are still unknown to date. It is not understood in which form these contaminations are existent in the helium liquid and cold gas phase. Furthermore, there are hints that neon co-contaminations might play some role. The present work strives for a better understanding at that point. It is planned to develop and to demonstrate measurement methods for such hydrogen and neon detection in the ppb range. This will be based on gas chromatography, moreover on a novel plasma emission spectroscopy apparatus. It is planned to get a better approach to the solubility limit of hydrogen in liquid helium. This shall be done by means of an optical bath cryostat with the detection of particles from frozen solid hydrogen by laser defraction. Variable defined contaminations shall be provided within the cryostat. Finally measurement procedures shall be developed allowing a detection of such contaminations in standard liquid helium dewars and cryostats, by means of a respective probe extraction method and using the demonstrated, optimized gas analyzers. Parallely a better thermodynamic understanding of the fluid system shall be elaborated.

• DFG Programme: Further Instrumentation Related Funding