A new, large‐area, high‐uniformity, flash x‐ray source that efficiently couples electrical energy to photon energy has been successfully constructed and tested on the 1‐MV, 2‐MA electron accelerator SPEED (short pulse experimental electron device). The source employs 18 individual blade diodes arranged in the configuration of a frustum. Each blade was magnetically isolated on the real‐cathode side of an anode foil, but not on the virtual‐cathode side. The operation of the diode was heavily diagnosed using 24 Rogowski coils, a vacuum voltage monitor, p‐i‐n diode detectors, an 80‐element TLD array, and a fast‐framing x‐ray pinhole carnera. The individual blade diodes were found to exhibit line pinching, end‐to‐end pinching, and minimal electron reflexing through the Ta anode foil, with a radiation yield that agreed with Monte Carlo simulations. The end‐to‐end pinch location could be controlled by tapering the anode–cathode gap. The impedance depended on only the smallest spacing, and was independent of pinch location.