When superfluidity meets superconductivity in the extraction of 3He isotope from liquid helium

Abstract

Abstract The world needs clean energy. One of the most promising ways of producing it in large amounts is the helium3-deuterium ( 3 $$\hbox {He-D}$$ He-D ) fusion reaction. Although there are numerous sources of 3 $$\hbox {He}$$ He on Earth, most of them are either difficult to access or unprofitable to operate. The main problem underlying the shortage of 3 $$\hbox {He}$$ He is the lack of an effective method of obtaining this isotope. Here we report the results of quantum filtration of 3 $$\hbox {He}$$ He from liquid helium in a superfluid state (below the $$\lambda$$ λ -transition), with the use of an entropy filter made of a high-temperature superconductor YBCO-123. During the operation of so-called fountain effect generated with this filter, unlike the other filters, we observed a strong increase of 3 $$\hbox {He}$$ He concentration downstream, where only pure $$^{4}\hbox {He}$$ 4 He was expected. This effect occurred due to the unique combination of two quantum phenomena—superfluidity and superconductivity, leading to the observation of a low-temperature rectification-like process. Rectification of helium isotopes does not require lowering the temperature below the $$\lambda$$ λ -transition, so the process can be more economical than filtration. Moreover, micro-superconductors could be applied also to the extraction of deuterium, thus allowing the same method to be used for both crucial components of the 3 $$\hbox {He-D}$$ He-D fusion. This method should be easy to upscale and could be used in space (with less energy input) as 3 $$\hbox {He}$$ He , the crucial isotope for future energy, is also sought beyond the Earth.