Biography: Dr. TONOMURA Akira

Akira TONOMURA joined the Central Research Laboratory of Hitachi, Ltd. in 1965, and since then has been engaged in research and development of electron beam physics and its application to electron microscopy.

In 1968, he obtained electron holograms for the first time in the world and reconstructed images using an electron microscope equipped with a thermal electron gun. However, since the reconstructed images were not as clear as those obtained with a conventional electron microscope, he discontinued his research into electron holography temporarily. Dr. Tonomura then turned his attention to R&D of scanning electron microscopes, with particular emphasis on the development of field emission guns to provide high beam brightness. This resulted in a field emission gun with a brightness two or three orders of magnitude higher than that of a thermal emission gun. This field-emission technology played an essential role in the realization of an holography electron microscope.

From 1973-74, Dr. Tonomura studied electron interferometry under Professor G. Mollenstedt at the University of Tubingen in Germany. On returning to the Central Research Laboratory, Tonomura restarted his research on holography electron microscopy in 1976, and two years later succeeded in making a high-coherence electron microscope, utilizing a high-performance field-emission gun developed by him and his colleagues. The resulting coherence was more than two orders of magnitude higher than that of a conventional microscope. This brought holography electron microscopy into the practical realm, making it possible to observe phase information contained in the electron beam transmitted by specimens at a much higher resolution. Use of this phase information enabled measurement of minute magnetic fields that cannot be directly observed. For this achievement, Dr. Tonomura received the Optics Paper Award from the Optical Society of Japan and the Sedo Prize from the Japanese Society of Electron Microscopy, both in 1980, and was commended as Persons of Scientific and Technological Research Merit by the Minister of State for Science and Technology (Science and Technology Agency, Japan) in 1984.

Dr. Tonomura and his colleagues then went on to use electron holography to experimentally verify the Aharonov-Bohm effect, thus ending a long-standing dispute on the existence of vector potential, i.e. the existence of a gauge field. For this achievement, Dr. Tonomura was awarded the Nishina Memorial Prize in 1982, the Asahi Prize in 1987, and the Japan Academy Prize and Imperial Prize in 1991.

In 1992, Dr. Tonomura and his colleagues developed a method to observe a magnetic flux line (vortex) inside superconductors. Pinning down vortices inside superconductors is necessary in order to obtain practical superconducting magnets. To do this, it was necessary to understand how vortices behave, and how they are affected by changes in current, magnetic field, and temperature. Using a 350kV holography electron microscope, the researchers succeeded in achieving the first dynamic observations of vortex motion in superconductors. For these achievements, Dr. Tonomura was awarded the Benjamin Franklin Medal in Physics in 1999.

In 2000, Dr. Tonomura and his colleagues developed a 1 million volt holography electron microscope. This had a beam brightness of 2x10¹⁰Acm^-2str^-1and lattice resolution of 49.5 pm, both world records. This latest microscope is also now being put to use for the direct observation of unconventional behavior of vortices in high-temperature superconductors.

Dr. Tonomura received the Cultural Merit award from the Ministry of Education, Culture, Sports, Science and Technology, Japan, in November 2002, and was elected as a Foreign Associate of the National Academy of Sciences in the United States of America in May 2000, a Foreign Associate of the Royal Society of Sciences at Uppsala in June 2003, and conferred with a Laurea Honoris Causa from the University of Camerino in July 2005. In December 2007, Dr. Tonomura was elected as a member of the Japan Academy.

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