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VA: Fachverband Vakuumphysik und Vakuumtechnik

VA 2: Vacuum technology: New developments and applications

VA 2.1: Hauptvortrag

Montag, 16. März 2020, 12:30–13:10, HSZ 301

Vacuum Solutions for Dilution Refrigerators — •Stefan Lausberg — Atlas Copco - Scientific Vacuum Division, Bonner Str. 498, 50968 Köln

Dilution refrigerators are cryostats that can reach base temperatures as low as 2 mK. The refrigerant they use are mixtures of 3He and 4He that contain about 1/5 of the rare and very expensive 3He. Like in all cryogenic applications, vacuum products play an essential role for dilution refrigerators. In 2019, the world market for dilution refrigerators has increased to more than 200 systems per year driven by the emerging quantum computing market. In consequence, the dilution refrigerator is a growing application for vacuum pumps and accessories like gauges.

Here, we will discuss the requirements for vacuum products in this type of cryostat. Besides pump systems for insulation vacuum and pumps to supply the dilution refrigerator's 1-K-pot, the heart of the cryostat is the 3He pump system. This system circulates the mixture in a closed loop and requires a maximum leak rate of 1E-7 mbar*l/s to preserve the expensive 3He. In order to achieve an enhanced cooling capacity the necessary 3He gas flows require a pumping speed that can only be reached by using a two-stage pump system. We will see that the most appropriate 3He vacuum pump system would be an oil-free, dust-free pump system with an optimized pumping speed in the range of 0.01 to 1 mbar. Even though the pressure range is not within the focus applications of turbomolecular pumps we will see some advantages over roots pumps at the second stage.