Liquid helium of liquid water. Helium was first liquefied on July 10, 1908, by the Dutch physicist Heike Kamerlingh Onnes at the University of Leiden in the Netherlands. At that time, helium-3 was unknown because the mass spectrometer had not yet been invented. In more recent decades, liquid helium has been used as a cryogenic refrigerant, and liquid helium is produced commercially for use in superconducting magnets such as those used in magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR), Magnetoencephalography (MEG), and experiments in physics, such as low temperature Mössbauer spectroscopy. The temperature required to produce liquid helium is low because
Mieczysław Wolfke K. Kamerlingh-Onnes and (later) Willem Keesom studied the dielectric constant of liquid helium at various temperatures. The theoretical experiments led him to the discovery of two liquid phases of helium and solidification of helium what Mieczysław Wolfke considered as the third of his greatest achievements. In the early thirties Wolfke started to organize the separated Institute of Low Temperatures at Warsaw University of Technology, even running the first installation. In 1927 Wolfke worked on the liquid helium dielectric constant and in the next year on the association in liquid dielectrics. He also started cooperation with the Polish Army in Temporary