Dry dilution refrigerator with anti-vibration system for mK scanning probe microscopy

NPL is seeking a solution for a new dry dilution refrigerator (“the system”) in which scanning probe microscopy experiments will be carried out at mK temperatures on live superconducting quantum circuits. NPL wishes to use the system for atomic scale scanning tunnelling microscopy and atomic force microscopy. As such, the system must provide a low vibration and high coherence environment (light tight mixing chamber volume). Significant emphasis will be placed on the lowest possible vibration levels that can be achieved. It is anticipated that a solution provides both a mK vibration isolation system and various vibration mitigation measures at room temperature.
The scope includes the dilution refrigerator having a low-vibration experimental platform at mK temperature, the experimental wiring tree to the mK experimental platform, and any room-temperature or low-temperature vibration reducing measures, any gas handling system, vacuum pumps or electronics required to operate the system. The system does not include the scanning probe microscopy unit itself, this will be provided and integrated by NPL.
In the below we denote “the mixing chamber plate” as the standard plate of the dilution refrigerator that reaches the specified temperature and cryogenic performance. We further specify an “experimental plate” which may be the same as the “mixing chamber plate” in some implementations, but it may for some vibration isolating solutions be a separate plate on which the experimental scanning probe system and apparatus is mounted. It is in that case assumed that the experimental plate is thermally anchored to the mixing chamber plate and reaches the same base temperature, and sits within the enclosed mixing chamber shielded volume.
Description
• A “dry” pulse tube cooled dilution refrigerator that does not use liquid nitrogen or liquid helium to achieve cooling to 4 Kelvin.
• The dilution refrigerator shall reach a base temperature of 20 mK or less at the vibration-isolated...