Periodic Reporting for period 1 - FunClocks (Testing Fundamental Physics with Highly Charged Ion Clocks)
Reporting period: 2022-01-01 to 2023-06-30
In parallel, preparations for isotope shift spectroscopy of the stable even Ca14+ isotopes started. A clock laser system was setup and stabilized to a stable reference cavity, transfer-locked to a Si-cavity stabilized laser at PTB. An extension of the electron beam ion trap was designed, built and commissioned to allow ablation loading of metal targets such as Calcium. Precision spectroscopy of 40, 42, 44, 46 and 48-Ca14+ at a level of 1e-16 (corresponding to <100 mHz resolution) was performed against the Yb+ octupole clock at PTB and the corresponding isotope shifts were extracted and combined with existing data on singly charged Calcium. Together with several other experimental and theory groups the quality of the previously existing data is currently being improved and an analysis in terms of exclusion of possible 5th force candidates is under way.
In preparation for the next HCI clock species, several search strategies for finding mHz narrow transitions within a frequency range of THz have been investigated and benchmarked. Of the investigated techniques based on Rabi spectroscopy, oscillating dipole forces and rapid adiabatic passage, the latter is by far the most efficient if a logic transition is available. A publication of the experimental results and theoretical modelling is in preparation.