Atomic physics techniques offer extraordinary control over both motion and internal degrees of freedom of individual quantum systems. This control has enabled the most accurate measurements e.g. in atomic clocks. At the same time, precision measurements allow to test fundamental and SM physics at a level corresponding to energy scales accessible only by the largest colliders. Two experimental efforts in this context will be presented in this talk.
The first experiment---within the HUNTER collaboration---is the search for keV-range sterile neutrinos, which present an interesting extension to the SM and could also be dark-matter constituents. We will start with the first-ever magneto-optical trap for cesium-131 which undergoes electron capture. The total reconstruction of the energies and momenta of the "visible" particles in a decay will be achieved with very high-resolution electrostatic ion and electron spectrometers, respectively, and state-of-the-art pixellated X-ray detectors. This reconstruction will allow to deduce the mass of the undetected neutrinos and keV-range (sterile) neutrino events will appear as a well-separated signal from ordinary neutrino events.
The second experimental effort is the search for the nuclear isomeric transition in thorium-229. Due to its exceptionally low energy, this transition is in the laser-accessible energy range around 150nm. Its unique properties make it the prime candidate for precision nuclear and fundamental physics tests as well as future optical clocks. Three experiments to narrow down the knowledge of the transition energy will be presented, all of which are currently conducted in parallel and exploit physically fundamentally different effects.