Cygnus dose symmetry

The Cygnus Dual Beam Radiographic Facility consists of two identical radiographic sources each with a dose rating of 4 Rad at 1 m, and a 1 mm diameter spot size. The development of the rod pinch diode was responsible for the ability to meet these criteria. The rod pinch diode in the Cygnus machines use a 0.75 mm diameter tungsten tapered anode rod extended through a 9 mm diameter cathode aperture. When properly configured, the electron beam born off the aperture edge can self-insulate and pinch onto the tip of the rod creating an intense, small x-ray source. The Cygnus sources are utilized as the primary diagnostic on experiments which are single-shot, high value events. In such an application there is an emphasis on reliability and reproducibility. The azimuthal quality and reproducibility of the Cygnus sources will be analyzed using lithium fluoride thermoluminescent dosimeters. Photogrammetry will be used to quantify the precision of the rod pinch diode build (i.e. the centeredness of the anode rod). One goal of these tests will be investigation of the relationship of dose symmetry to anode rod position (i.e. the correlation of off-center dose to an off-center anode rod).