Sketch of the SKP instrument. Left side: view inside the chamber. The miniaturized and shielded pre-amplifier ensure a high signal-to-noise ratio. The cooling plate below the sample stage enables temperature-controlled measurements of potential changes during superficial and/or interfacial melting of solids (not shown here). The X-ray beam enters and exits the chamber through metalized Kapton windows. Right side: side view of the SKP instrument. Two separate XY motor stages allow translation with respect to the fixed X-ray beam for both the needle and sample independently.