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Millions in funding for clock project


PTB’s researchers, together with international colleagues, have secured a prestigious Synergy Grant from the European Research Council (ERC) for the development of an entirely new atomic clock – the thorium nuclear clock. A thorium nuclear clock could be significantly more accurate than all the previous caesium clocks and – also – than all the previous optical atomic clocks.

Stylized representation of a nuclear clock based on a transition in the atomic nucleus of heavy thorium-229. The principle of this clock consists in exciting the nucleus with laser light. In the background: Section of the table of nuclides around thorium-229. (Source of picture: Christoph Düllmann, JGU Mainz)

In atomic clocks as we have known them, it is the atomic shell that “ticks”, whereas this is done by the atomic nucleus in thorium clocks. As inside the atomic nucleus, the protons and neutrons are packed together much more tightly and are more strongly bonded than the electrons in the outer shell, a clock based on the atomic nucleus is much more promising in terms of accuracy than previous atomic clocks. That entails advantages for high-precision time and frequency measurement applications and for fundamental physics research. Now that the international research consortium has already shown in several publications that such a clock is, in principle, feasible, the European Research Council has demonstrated its confidence in the project by providing it with funds amounting to a total of 13.8 million euros. In addition to researchers from the PTB, scientists from Vienna, Munich, Delaware (USA), Heidelberg and Aachen are participating in the interdisciplinary and international “Thorium Nuclear Clock” project.