Regensburg 2025 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 11: Superconductivity: Poster
TT 11.65: Poster
Monday, March 17, 2025, 15:00–18:00, P4
Towards Phonon Detection in Superfluid Helium with MMCs — •Axel Brunold, Andreas Fleischmann, and Christian Enss — Kirchhoff Institute for Physics, Heidelberg University
The search for light dark matter requires innovative detection techniques that can probe weakly interacting particles with exceptional sensitivity. One promising approach involves studying elastic scattering interactions between dark matter particles and helium atoms at millikelvin temperatures.
As part of the "Direct search Experiment for Light dark matter", DELight, a pilot experiment is conducted to investigate the behavior of metallic magnetic calorimeters (MMCs) submerged in liquid helium. MMCs have previously demonstrated the capability to detect photons with high energy resolution and linearity; this experiment seeks to explore how these properties translate to the detection of phonons. In this setup, a small copper cell (300 ml) is cooled to below 1 K within a 3He/4He dilution refrigerator and filled with 4He. The liquid helium level, while filling and later on operating the MMC, is monitored with an LC circuit-based level meter. At these millikelvin temperatures, 4He is deep in its superfluid phase, enabling a long mean free path for phonons and rotons. A resistive heater is used to excite phonons, which are then collected by an MMC on a 5 mm x 5 mm silicon substrate. This contribution presents the setup and first results.
Keywords: Metallic Magnetic Calorimeter; Superfluidity; Dark Matter