Electric field compensation and sensing with a single ion in a planar   trap
  We use a single ion as an movable electric field sensor with accuracies on the order of a few V/m. For this, we compensate undesired static electric fields in a planar RF trap and characterize the static fields over an extended region along the trap axis. We observe a strong buildup of stray charges around the loading region on the trap resulting in an electric field of up to 1.3 kV/m at the ion position. We also find that the profile of the stray field remains constant over a time span of a few months. 
Sankaranarayanan Selvarajan, Nikos Daniilidis, S\"onke M\"oller, Rob   Clark, Frank Ziesel, Kilian Singer, Ferdinand Schmidt...
physics.atom-ph physics.ins-det quant-ph