Profile
David Keeble
My CV
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Current Job:
Professor, Head of Physics
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The most exciting thing that's happened this year in my research area:
The positron is the anti-particle of the electron, same mass, spin, magnetic moment, but opposite charge. A team in Italy reported the observation of antimatter wave interference of single positrons. A single positron passes through the experiment in 10 nanoseconds, there is approximately 10 milliseconds between each positron. The positrons pass through two simple gratings, separated by 118 millimeters, each with a repeat of about 1 micrometer, then the positron is detected on a nuclear emulsion detector and its position identified. The distribution of positions of the detected positrons clearly demonstrate that particle wave interference has occurred.
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My latest work:
One of our current projects is as part of a collaboration led by colleagues at National Institute of Advanced Industrial Science and Technology in Japan. It is an international collaboration performing positron lifetime measurements on the same series of well characterized materials that have nano-meter size open-volume (pores or voids) in a number of laboratories across the world. In the materials we are measuring some, in fact the majority, of the positrons we implant move into the nano-meter size open spaces, picking up an electron on the way, and forming what is called a positronium atoms. This is a electron bound to its anti-particle the positron. Those positronium atoms that form where the spins of the two particles are aligned would live for approximately 142 nanoseconds in a vacuum. This is a very long time to us as we typically measure lifetimes a thousand times smaller. However, these positronium atoms ‘bounce’ about inside the pore in the material and so annihilate typically after only a few nanoseconds. From the actual lifetime of the positronium we can calculate the approximate diameter of the pore. Materials scientists cannot easily measure pores/voids with nano-meter size. Our collaboration is aiming to produce standard samples and guidance on how to perform the measurements so that this method can be more widely used.