Project Details
Projekt
Cryogenic setup and superfluid helium cell
Subject Area
Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
Term
since 2026
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 561595909
DELight is a new particle physics experiment to search for light dark matter (LDM) particles with masses well below 1 GeV/c2 by detecting elastic LDM scattering off a cryogenic liquid helium (LHe) target. Its low mass number, the low threshold achievable with magnetic microcalorimeters (MMCs), its intrinsic radiopurity and the availability of several signal channels render LHe an ideal target for LDM searches. DELight can only be realized through the confluence of its six projects. Each project plays a fundamental and unique role, where this project is responsible for developing, designing and constructing the superfluid helium cell, and the cryogenic platform of the experiment. A number of specific requirements must be met for the cell itself and the cryogenic environment in which it is operated. The cell temperature should be well below the superfluid transition to maximize the superfluid component and minimize scattering with thermal excitations. The operating temperature should be below 20\,mK. This requires cooling the cell with a dilution refrigerator with sufficient cooling power and space for the cell and a film burner that is required to evaporate the superfluid film creeping up the walls of the cell. It should also be possible to operate the cryostat remotely. Here, a commercial dry dilution refrigerator with two independent dilution units will be used as cryogenic platform and adapted to the specific needs of the project. The superfluid 4He itself must be purified and, in particular, freed from 3He impurities in order to not impede the mean free path of the athermal quasiparticles generated in an event. For this purpose, a suitable heat-flush purifier operating at low temperatures and a super leak will be developed and integrated into the cryogenic setup. A sensitive level sensor is also needed to monitor the helium level in the cell. At the same time R&D projects are conducted that are necessary for a second phase of the DELight experiment. These include investigating the quasiparticle signal with wafer-calorimeters within the liquid, the development of a quasiparticle reflection system and the development of alternative film creep suppressing schemes.
DFG Programme
Research Units
Subproject of
FOR 6006:
DELight: Direct Search Experiment for Light Dark Matter with Superfluid Helium
Co-Investigators
Professor Dr. Sebastian Kempf; Dr. Sebastian Lindemann
