Superconductors
Perfect diamagnetism. The Meissner effect expelling the field entirely, a magnet hanging above a YBCO pellet in liquid nitrogen, flux pinning and the locked-in-place trick, and the maglev demonstrations built from it.
Part of Diamagnetism
13 moments in this segment.
- - The Leiden cryogenic laboratory, room E, 1900. The cryogenic laboratory at the Steenschuur in Leiden photographed in 1900, eleven years before the discovery of superconductivity. It shows the compressors and cascade plant that Kamerlingh Onnes built to chase ever lower temperatures. Small (400x560) but a real, dated interior of the actual room.
- - The apparatus that first liquefied helium, 10 July 1908. The installation with which Kamerlingh Onnes liquefied helium for the first time on 10 July 1908 at the Steenschuur laboratory in Leiden. Liquid helium is what made the 1911 superconductivity experiment possible at all. 400x589.
- - Kamerlingh Onnes's 1911 resistance-versus-temperature plot for mercury. The original 1911 graph in which the resistance of a mercury capillary falls vertically to zero just below 4.2 kelvin. This is the primary document of the discovery of superconductivity, drawn by Kamerlingh Onnes's own laboratory. Nothing else in the story is this directly evidential.
- - First Solvay Conference, Brussels, 1911. The first Solvay Conference, Brussels, 2 November 1911 - Kamerlingh Onnes is in the group, the same year he discovered superconductivity. It fixes the moment in the wider history of physics. 1920x1362.
- - Kamerlingh Onnes and Gerrit Jan Flim at the second helium liquefier, 1919. Kamerlingh Onnes standing with Gerrit Jan Flim, the chief of the cryogenic laboratory, beside the second helium liquefier in 1919. Flim was the instrument-maker who actually built and ran the plant. A rare shot of the human machinery behind the discovery.
- - Heike Kamerlingh Onnes. A portrait of Heike Kamerlingh Onnes, the Leiden physicist who liquefied helium in 1908 and then, in April 1911, found that mercury lost all electrical resistance below about 4.2 kelvin. Superconductivity turned out to be the extreme case of diamagnetism. 1200x1676.
- - Solvay Conference 1927, with Langevin presiding. The 1927 Solvay Conference photograph, the most famous group portrait in physics; Paul Langevin sits at the right-hand end of the front row, having chaired the meeting. It places the author of the theory of diamagnetism inside the founding generation of quantum mechanics - which is exactly where the diamagnetism story goes next.
- - Magnetic flux expelled from a tin cylinder at 1.6 K. A laboratory photograph of the field around a tin cylinder cooled from 4.2 K to 1.6 K in a constant 80-gauss field: as the tin goes superconducting, the flux is pushed out of it. This is the Meissner-Ochsenfeld effect recorded on the same metal Meissner used. Dated 1964, so far closer to the original era than any modern demo.
- - Walther Meissner. A portrait of Walther Meissner, who with Robert Ochsenfeld showed in 1933 that a superconductor does not merely fail to resist current but actively expels magnetic field from its interior - perfect diamagnetism. This is the result that made superconductivity a magnetic phenomenon, not just an electrical one.
- - Flux pinning / quantum locking. A superconducting disc locked at a fixed height and angle above a magnetic track by flux pinning. It shows the limit of the diamagnetic story: a type-II superconductor lets some field through in quantised vortices and is then trapped in place. 2034x1375.
- - The Meissner effect, demonstrated. Harvard’s lecture demonstration of the Meissner effect: cool a superconductor below its critical temperature and it expels the magnetic field entirely, floating the magnet above it. Meissner and Ochsenfeld first showed this with tin and lead in 1933.
- - A magnet levitating above a superconductor cooled in liquid nitrogen. A permanent magnet floating above a high-temperature superconductor in a pool of liquid nitrogen vapour. The magnet is held up by the field the superconductor refuses to let inside it - the Meissner effect, i.e. perfect diamagnetism, made visible. 4048x3036.
- - Meissner state demonstration. A close view of the Meissner state, with a magnet suspended in mid-air over a chilled superconductor. A cleaner, more diagrammatic alternative to the liquid-nitrogen photograph. 1280x960.
