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Image: Nuclear clock concept

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Description: A Thorium-229 nucleus is irradiated with stabilized laser light (Laser 1). A second Laser (Laser 2) is used to probe the atomic shell's hyperfinestructure in order to determine via the change of the nuclear spin state if the nucleus was successfully excited. A photomultiplier tube (PMT) is used to probe if Laser 2 is on resonance. Based on the PMT signal Laser 1 is actively stabilized to the nuclear transition via a feedbackloop. In this way the frequency of Laser 1 will exactly match the frequency of the nuclear excitation. The frequency of Laser 1 can be accurately measured with the help of a frequency comb and therefore used as a time and frequency standard.
Author: LarsvdW
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