kiutra combines multi-stage magnetic refrigeration and closed-cycle precooling to provide Kelvin and sub-Kelvin temperatures cryogen-free and continuously.

Our cooling systems offer an elegant and convenient way to generate very low temperatures:

  • all-electrical, completely cryogen-free operation
  • minimal infrastructure and space requirements
  • hazard-free, convenient, and fully automatic operation
  • magnetic low-temperature control with excellent precision and stability

How it works

Magnetic refrigeration is based on the magneto-caloric effect (MCE): When a medium is magnetized its magnetic moments get aligned and the heat of magnetization is released. Vice versa, if the medium is demagnetized its temperature drops.

Cooling systems by kiutra make use of two different types of magnetic refrigeration to meet the cooling demands of each individual customer:

Pulsed Adiabatic Demagnetization Refrigeration (ADR)

As shown schematically in the figure below magnetic refrigeration may be used to generate short-term cooling. Starting from an initial temperature provided by a closed-cycle cryocooler, a suitable cooling medium is first magnetized (1→2). The heat of magnetization is dissipated by the cryocooler (2→3). Subsequently, the medium is thermally decoupled by means of a so-called heat switch and demagnetized. During the demagnetization process the temperature of the cooling medium drops (3→4). As the magnetic field is lowered to zero cooling power vanishes. Therefore, the medium finally warms up again.
Alternatively, during the last step the magnetic field may be reduced not to zero but only to an intermediate value. This allows to tune in low temperatures for up to several hours. During the hold time our magnetic temperature control (free of fault-prone heaters, valves, or capillaries) offers excellent precision and stability.

Working principle of the pulsed ADR method.

Continuous Adiabatic Demagnetization Refrigeration (CADR)

Sometimes pulsed cooling is not sufficient. For these applications kiutra offers cryogen-free magnetic heat pumps which provide permanent cooling power. These systems are based on multi-stage magnetic refrigeration, where we interconnect and carefully balance several magnetic cooling units. The trick: The heat of magnetization released in the nth cooling unit is dissipated by the (n-1)th unit, and so on… This ensures that the final cooling unit never runs out of magnetic field and hence provides Kelvin or sub-Kelvin temperatures continuously.

Continuous ADR shown schematically for a 3-stage magnetic cooling system.

Magnetic refrigeration systems by kiutra offer both Pulsed and Continuous ADR in a highly modular assembly. Depending on customer-specific demands Pulsed ADR systems can be upgraded to multi-stage CADR refrigerators.

All our cooling solutions operate fully automatically.