Abstract: Electron gun. The electron gun includes a circular cathode. The circular cathode comprises a spherical surface. The electron gun further includes a focus electrode. The focus electrode has four quadrants. The focus electrode is disposed about the circular cathode. The focus electrode includes four primary focus angle points. At least two of the four, adjacent, primary focus angle points have different angle values. Each of the four primary focus angle points is in a different quadrant. Focus angles on the focus electrode between any two primary focus angle points vary from one primary focus angle point to another primary focus angle point.