Dresden 2026 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 22: Superconductivity – Poster I
TT 22.37: Poster
Montag, 9. März 2026, 18:00–20:00, P1
Purification of liquid Helium with a heat flush purifier in a dry cryostat — •Franziska Hömke and for the DELight Collaboration — Kirchhoff-Institute for Physics, 69120 Heidelberg, INF 227, Germany
The Direct search Experiment for Light dark matter (DELight) aims to search for dark matter by probing elastic scattering interactions of light dark matter particles with helium atoms in liquid helium. The helium is cooled to low millikelvin temperatures within a 3He/4He dilution refrigerator. At these temperatures 4He is in its superfluid phase, enabling a long mean free path for the phonons and rotons produced in the scattering events. However, 3He impurities drastically limit the mean free path and hinder the ballistic propagation of the phonons and rotons. To achieve a sufficiently large mean free path, the 3He concentration in the helium must be reduced by at least three orders of magnitude from the natural concentration.
A heat flush purifier makes use of the unique properties of superfluid 4He to remove 3He and other impurities via a temperature gradient. It can be operated in continuous flow and will be integrated into the helium filling circuit of the cell. In wet cryostats, these devices were able to achieve the desired 3He concentration in 4He within a single cycle, but no implementations in dry cryostats have yet been described.
This contribution presents the ongoing developments in the design and optimization of a heat flush purifier for the DELight cell.
Keywords: Helium; Dark Matter; Superfluidity; Isotope Separation; Heat Flush