kiutra combines multi-stage magnetic refrigeration and closed-cycle pre-cooling to provide Kelvin to sub-Kelvin temperatures cryogen-free and continuously.
Our cooling systems offer an elegant and convenient way to generate very low temperatures verging on absolute zero (–273.15°C):
How it works
Magnetic refrigeration is based on the magneto-caloric effect: 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 can make use of two different types of magnetic refrigeration methods:
Single-shot Adiabatic Demagnetization Refrigeration (ADR)
As shown schematically in the figures above, magnetic refrigeration may be used to generate short-term cooling. Starting from an initial base temperature provided by a closed-cycle cryocooler (Step 1), a suitable cooling medium is first magnetized (Step 2). The heat of magnetization is then dissipated by the cryocooler (Step 3). Subsequently, the cooling medium is thermally decoupled by means of a so-called heat switch (Step 4) and then demagnetized afterwards (Step 5). During the demagnetization process the temperature of the cooling medium drops. If the set-point temperature is reached before the magnetic field, B, is lowered to zero the cooling power can be regulated to provide constant temperature over time, e.g. for several hours or even some days (Step 6). When the magnetic field is finally decreased to zero, the cooling process stops (Step 7) and the medium warms up to base temperature again (Step 8). The process can be restarted after some waiting time.
For some applications single-shot 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 several magnetic cooling units are interconnected and carefully balanced, as shown schematically in the figure above. 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, connected to the sample stage never runs out of magnetic field, and hence can provide Kelvin or even sub-Kelvin temperatures continuously – in principle infinitely long.
Magnetic refrigeration systems by kiutra offer both single-shot and continuous ADR in a highly modular assembly. Depending on customer-specific demands single-shot ADR systems can be upgraded to multi-stage CADR refrigerators.