Project Details
Projekt
Pulse-tube-cooled 3He/4He dilution refrigerator with two dilution units
Subject Area
Particles, Nuclei and Fields
Term
since 2026
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 580662618
The Kirchhoff-Institute for Physics at Heidelberg University, in collaboration with related institutes at the Karlsruhe Institute of Technology and the University of Freiburg, is planning a direct dark matter detection experiment, DELight (Direct search Experiment for Light dark matter). Over the coming years, the DELight experiment will be constructed, commissioned, and begin its searches for dark matter interactions in a superfluid 4He target. The observation of such interactions will provide unambiguous evidence for the particle nature of dark matter, addressing one of the most profound open questions in modern physics. DELight will proceed in multiple phases, with a progressively increasing helium target volume and continuous improvements in energy resolution, detection threshold, and background levels, establishing a long-term science program spanning more than a decade. A pulse-tube-cooled 3He/4He dilution refrigerator, in a non-standard configuration with two dilution units, is indispensable for DELight, where each dilution unit serves a different purpose. One dilution unit will provide a base temperature below 10 mK to cool the helium into its superfluid state and minimize quasiparticle scattering sites in the superfluid, and to enable the operation of ultra-sensitive large-area microcalorimeters (LAMCALs) for high-resolution energy and time measurements. The second dilution unit will support a helium-film burner system, an indispensable component of the DELight detector, operating above 100 mK. The design of the film burner is following the successful design developed and operated as part of the superfluid-helium-based HERON neutrino project. The LAMCALs are based on magnetic microcalorimeter (MMC) technology which operate at low millikelvin temperatures. One part of the LAMCALs will be positioned above the helium volume in vacuum, the other part will be submerged. The required size, two-unit system, cooling power, and technical specifications of the dilution refrigerator are determined by the size of the helium volume, the amount of LAMCALs and in particular by the operation of the helium-film burner, which prevents film formation on the subset of microcalorimeters that must operate film-free in vacuum. At the same time, the chosen specifications ensure that the dilution refrigerator will remain suitable for research and development (R&D) and for future applications, e.g., R&D in the field of quantum computing, even if the DELight experiment eventually exceeds the refrigerator’s capacity and also DELight R&D for future phases does not require permanent access to the instrumentation anymore.
DFG Programme
Major Research Instrumentation
Major Instrumentation
Pulsrohrgekühlter 3He/4He-Verdünnungskryostat mit zwei Verdünnungseinheiten
Instrumentation Group
8550 Spezielle Kryostaten (für tiefste Temperaturen)
Applicant Institution
Ruprecht-Karls-Universität Heidelberg
