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Joined 2026-09-21 Message
Incoming links: Electron holography
Akira Tonomura 2026-10-18
A physicist who developed electron holography and investigated the Aharonov-Bohm effect.[ref]
Benjamin Franklin Medal Awarded to Akira Tonomura, Senior Chief Research Scientist at Hitachi, Ltd.. Opening paragraph: Senior Chief Research Scientist; development of holography electron microscopy
Electron biprism 2026-10-18
An electron biprism uses the electric field around a biased fine wire to overlap coherent Electron waves for interference. It provides object–reference overlap in electron holography.[ref]
Electron holography 2026-10-18
Electron holography uses Electron object and reference waves to encode their relative wave phase in a hologram.[ref]
Shielded toroidal-flux electron interference 2026-10-18
In 1986, Akira Tonomura and collaborators coated a ferromagnet shaped as a torus with superconducting niobium and copper. A cooled stage held it in a 150 kV field-emission electron microscope. An electron biprism overlapped object and reference waves; film holograms were reconstructed optically. Room-temperature leakage screening selected samples; varying copper thickness tested electron penetration.[ref]
Below the superconducting transition, through-hole and outside Electron waves differed in wave phase by zero or modulo . Warming through it changed the interference reversibly. Leakage and coherent-penetration bounds do not prove zero magnetic field.[ref]
Evidence for Aharonov-Bohm effect with magnetic field completely shielded from electron wave by Akira Tonomura and others. p. 794, Figs. 6–7: experimental limits
Why these two phases? The shield's superconducting flux quantum is , whereas the probing Electron has electric charge . Substituting givesAn odd therefore moves a carrier fringe by half its spacing; an even leaves it unchanged modulo a full spacing. The phase quantization provides an internal check on the superconducting enclosure. It does not mean that zero wave phase proves zero trapped magnetic flux.[ref]
The Aharonov-Bohm effect and its applications to electron phase microscopy by Akira Tonomura. 2006, p. 49, Confirmation experiments on the AB effect; Fig. 2 on p. 48
The readout is electron holography in the off-axis holography geometry: a known tilted reference converts an unknown relative wave phase into a spatial carrier displacement. Reconstructing a magnetic wave phase assumes stable reference phase, adequate coherence and a calibrated carrier; electrostatic charging and material traversal can also shift wave phase. Optical wave phase amplification rescales the displayed fringe displacement. The experiment's shielding and comparison tests support the magnetic inference; an interferogram by itself measures the total relative wave phase, rather than separately certifying every contribution. The ideal field-free model describes the limiting geometry, while finite leakage and penetration remain questions of experimental bounds.