Sub-Kelvin Refrigerator

Sub-K refrigerator (registered trademark: Ucryo^®) include two types of split continuous sub-K refrigerator and integrated sub-K refrigerator, which are widely used in the fields of condensed matter physics, electromagnetic transport, high-energy physics, astrophysics, superconducting materials, and quantum science and technology. 

The cold source of the split continuous sub-K refrigerator (model: Ucryo-100) comes from a helium cycle cryogenic system (Qcryo^®). The sub-K cryostat and the 4K cold head are separate (split design), and the cryogenic helium produced by the Qcryo^® is transferred via flexible super-adiabatic piping to the sub-K cryostat, where it is used for the condensation of another way of circulating helium gas from the externally integrated vacuum pump unit. This split design is characterized by the fact that the vibrations of the cold head and compressor are completely isolated from the sub-K cryostat, making it particularly suitable for vibration-sensitive experiments.

The 4K cold head of the integrated sub-K refrigerator is integrated into the sub-K refrigerator, from the working mode can be divided into integrated continuous sub-K refrigerator (model: Ucryo-200) and integrated single-shot sub-K refrigerator (model: Ucryo-300) two types. Among them, the integrated continuous sub-K refrigerator is equipped with an external circulating gas circuit and vacuum pump unit. On the other hand, the integrated single-shot sub-K refrigerator has a helium reservoir on the top, an integrated He-4 pot, a cryosuction pump and sealed piping inside. The helium gas inside the helium reservoir flows into the He-4 pot after condensing through the 4K cold head, and then the built-in cryosuction pump reducers the He-4 pot to the lowest temperature.

1.Split Continuous Sub-K Refrigerator

Model: Ucryo-100

The split continuous sub-K refrigerator is a split design consisting of a helium cycle cryogenic system (Qcryo^®) and a sub-K cryostat. This split design completely isolates the vibration of the 4K refrigerator cold head and compressor from the sub-K cryostat, making it particularly suitable for vibration-sensitive cryogenic experiments (e.g., STM, SEM, AFM, microscopy, single-quantum-dot, single-photon detection, etc.). 

The cryogenic helium produced by Qcryo^® is transferred via a flexible super-adiabatic line to the sub-K cryostat, where it is used to condense the circulating helium gas from another external integrated vacuum pump unit. The split continuous sub-K refrigerator has an external vacuum pump unit and a gas recirculation processing gas circuit, allowing continuous operation for long periods at<850 mK. Higher pumping speeds and thicker pumping lines are available as an option for temperatures down to <800mK.  

Split Continuous sub-K Refrigerator Example

Typical Cooling Curves for Ucryo-100 Split Continuous sub-K Refrigerator

Ucryo-100 Split Continuous Sub-K Refrigerator Minimum Temperature vs. Time

The Split Continuous sub-K refrigerator offers a wide range of options such as ultra-high vacuum compatibility, superconducting magnets with compact tail-matched room-temperature bore, top/side optical windows, built-in nanopositioning stage and objective lenses, RF semi-steel cables and optical fibers, etc.

Ucryo-100 Split Continuous Sub-K Refrigerator with Four Side Windows and One Top Window

Ucryo-100 Split Continuous Sub-K Refrigerator with Tail (Matching Room Temperature Bore Superconducting Magnet)

2.Integrated Continuous Sub-K Refrigerator 

Model: Ucryo-200

The integrated continuous sub-K refrigerator (model: Ucryo-200) uses a 4K PT or GM cryocooler as the cold source, and efficiently pre-cools and condenses the helium gas through multi-stage heat exchange and flow resistance, combined with an external sealed recirculation gas circuit to ensure that the integrated continuous sub-K refrigerator can operate continuously for a long period of time at the lowest temperature (<860mK), and the high-performance thermal switch shortens the initial cooling time. Optional vibration damping technology such as valve body separated PT cryocooler and cold head suspension vibration damping technology, vibration level is less than 100nm. Optional higher pumping speed circulating pump unit and thicker pumping line, the lowest temperature <800mK.

Example of an Integrated Continuous Sub-K Refrigerator

3.Integrated Single-Shot Sub-K Refrigerator

Ucryo-300

The integrated single-shot sub-K refrigerator adopts PT cryocooler or GM cryocooler as the cold source, with a reservoir integrated on the top, and He-4 pot, cryosuction pump and sealing piping integrated inside the cryostat of the refrigerator. The He-4 in the helium reservoir is condensed and flowed into the He-4 pot, and the built-in cryosuction pump can reduce the He-4 pot to 780 mK or below, and it can keep the lowest temperature for more than 100 hrs. The integrated single-shot sub-K refrigerator is characterized by simple design, low cost and low maintenance cost.

Integrated one-shot sub-K refrigerator （Ucryo-300）

Typical cooling curve of integrated single-shot sub-K refrigerator (Ucryo-300)