Electron beam characterization via quantum coherent electric field imaging

We demonstrate an all-optical, minimally invasive electron beam ( e − beam ) characterization using Rydberg electrometry. An e -beam passes through a localized detector volume containing thermal Rb atoms that are optically excited in a quantum superposition of ground and Rydberg states. The e -beam's electric field perturbs atomic coherence and modifies resonance fluorescence in a narrow spectral region near the two-photon optical transition. Imaging Rb fluorescence provides a map of the electric field from the e -beam via Rydberg state Stark shifts and allows us to reconstruct the e -beam width, centroid position, and current. For an e -beam of 20 keV and electron currents of 20–40 µ A , we measured the centroid position with an accuracy of ≤ 8 µ m and width to within 100 µ m , limited by the experimental sensitivity of electric field reconstruction of ∼ 0.02 V/cm. This method is suitable for a wide range of electron energies and currents, and can be adopted for nuclear and high-energy experiments for minimally invasive real-time diagnostics and profiling of charged particle beams.