KNF Pumps Push the Boundaries of Low Temperature Technology

Approaching Absolute Zero

With the ability to reach and maintain temperatures as low as 4.15 °K (-269 °C; -452 °F), which is close to absolute zero – the lowest temperature that can theoretically be reached – cryotechnology has become indispensable in many fields. Their applications range from scientific research to industrial processes where precise temperature control is essential. For example, scientists rely on cryostats to delve into the realms of quantum physics, superconductivity, and the properties of matter at the molecular and atomic levels. These systems are also invaluable in cryopreservation, where they help preserve biological samples at ultra-low temperatures, driving advances in regenerative medicine and biobanking.

From Vapor to Liquid: How Helium Enables Low-Temperature Cooling

The heart of a cryostat is its continuous flow system, which utilizes the cooling capabilities of liquid helium. This process vaporizes and expands the liquefied helium, creating a powerful cooling effect. A pump then transfers the resulting gaseous helium and slightly compresses it to feed a larger compressor, which re-liquefies the helium again.
 
The temperature range achievable with a conventional liquid helium-4 (⁴He) bath can be further reduced by using the rare helium isotope helium-3 (³He), allowing cryostats to reach even lower temperatures. Unlike the common helium-4 isotope, helium-3 has a much higher vapor pressure at the same temperature, allowing the temperature range to be extended down to 0.3 Kelvin. It is mainly used for its quantum mechanical properties, which are of interest in several fields of research. For example, helium-3 can enable certain phenomena at extremely low temperatures, such as the formation of Bose-Einstein condensates. However, due to the ultra-rare nature of helium-3, it is essential to use a tightly sealed system to prevent the valuable and therefore very expensive gas from escaping into the atmosphere and to ensure optimum compressor performance and efficiency. KNF pumps with particularly low leakage rates, such as the N 630, play a key role in meeting these requirements.

As with most KNF pumps, the N 630 gas pump can therefore be customized to meet the specific needs of cryostat systems, where its primary function is to maintain a tight seal, preventing helium from escaping and air from entering. It also plays a critical role in maintaining the helium pressure and flow required for the efficient operation of both the compressor and the helium re-liquefaction process. Since continuous refrigeration relies heavily on pumps, a customized KNF gas pump is ideally suited to the demands of cryostats, ensuring reliable performance while minimizing helium losses and improving overall operational efficiency.