A Digital Feedback System for Advanced Ion Manipulation Techniques in Penning Traps

Abstract: The possibility to apply active feedback to a single ion in a Penning trap using a fully digital system is demonstrated. Previously realized feedback systems rely on analog circuits that are susceptible to environmental fluctuations and long term drifts, as well as being limited to the specific task they were designed for. The presented system is implemented using an FPGA-based platform (STEMlab), offering greater flexibility, higher temporal stability and the possibility for highly dynamic variation of feedback parameters. The system's capabilities were demonstrated by applying feedback to the ion detection system primarily consisting of a resonant circuit. This allowed shifts in its resonance frequency of up to several kHz and free modification of its quality factor within two orders of magnitude, which reduces the temperature of a single ion by a factor of 6. Furthermore, a phase-sensitive detection technique for the axial ion oscillation was implemented, which reduces the current measurement time by two orders of magnitude while simultaneously eliminating model-related systematic uncertainties. The use of FPGA technology allowed the implementation of a fully-featured data acquisition system, making it possible to realize feedback techniques that require constant monitoring of the ion signal. This was successfully used to implement a single-ion self-excited oscillator.