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
Leiden if there's a Sunday involved) and includes parades, a hutspot feast, historical reenactments, a funfair and other events. The city has recently started to host the Leiden International Film Festival, the fastest growing festival of its type in the Netherlands. Leiden has important functions as a shopping and trade centre for communities around the city. The University of Leiden is famous for its many discoveries including Snells law (by Willebrord Snellius), the famous Leyden jar, a capacitor made from a glass jar, invented in Leiden by Pieter van Musschenbroek in 1746. Another development was in cryogenics: Heike Kamerlingh Onnes (1913