Massive quantum cold: Scientists modify ordinary lab refrigerator to cool faster with less energy

By improving a refrigerator commonly used in research and industry, researchers at the National Institute of Standards and Technology (NIST) have significantly reduced the time and energy required to cool materials to within a few degrees above absolute zero.

The scientists say they are currently working with industrial partners to commercialize their prototype device, which is expected to save 27 million watts of electricity, $30 million in global electricity consumption, and enough cooling water to fill 5,000 Olympic swimming pools per year.

From stabilizing qubits, the basic units of information in quantum computers, to maintaining the superconducting properties of materials to keeping NASA’s James Webb Space Telescope cool enough to observe the sky, ultracold refrigeration is essential for many devices and sensors operation is crucial. For decades, pulse tube cryocoolers (PTRs) have been the workhorse for achieving temperatures as cold as the vacuum of outer space.

These refrigerators cycle compress (heat) and expand (cool) high-pressure helium to achieve “big cold,” roughly similar to the way home refrigerators use Freon’s transition from liquid to vapor to remove heat. The PTR has proven its reliability for more than 40 years, but it is also very power-hungry, consuming more power than any other component of ultra-low temperature experiments.

When NIST researcher Ryan Snodgrass and his colleagues took a closer look at the refrigerator, they found that the manufacturer built the device to be energy efficient only at its final operating temperature of 4 Kelvin (K), or 4 degrees above absolute zero. The team found that these refrigerators were extremely inefficient at higher temperatures, which is a big problem because the cooling process begins at room temperature.

In a series of experiments, Snodgrass and NIST scientists Joel Ullom, Vincent Kotsubo and Scott Backhaus found that at room temperature, helium is under such high pressure that some of it is diverted through a safety valve instead of being used for cooling. By changing the mechanical connection between the compressor and the refrigerator, the team ensured that no helium was wasted, significantly increasing the refrigerator’s efficiency.

In particular, the researchers continually tweaked a series of valves to control the amount of helium flowing from the compressor to the refrigerator. The scientists found that if they allowed the valves to have wider openings at room temperature and then gradually closed them as cooling progressed, they could reduce the cooling time to between one-half and one-quarter of what it is now.

Currently, scientists must wait a day or more for new quantum circuits to cool down enough for testing. Since the progress of scientific research can be limited by the time required to reach cryogenic temperatures, the faster cooling provided by this technology could have broad implications for many areas, including quantum computing and other areas of quantum research.

Snodgrass said the technology developed by the NIST team could also allow scientists to replace large pulse-tube refrigerators with smaller pulse-tube refrigerators that require less supporting infrastructure.

As quantum computing research and its reliance on cryogenic technology continues to grow, the need for these refrigerators will increase significantly. The improved PTR will save more money, electricity and cooling water. In addition to supporting the emerging quantum economy, the device will speed up research because scientists will no longer have to wait days or weeks for qubits and other quantum components to cool.

Paper published in journal nature communications.

This story is reproduced courtesy of NIST. Read the original story here.