Assessment of the rod-pinch as a 1-2 MV radiography source on the NRL Gamble II generator

Summary form only given. A cylindrical pinched beam diode operating in the 1-2 MV, 30-60 kA, 25-50 ns (FWHM) range, was fielded on the Gamble II generator in order to assess the suitability of the resulting pinch as an X-ray source for high resolution radiography. The diode incorporated a 3.2 mm-long, 11 mm-diameter graphite cathode and a 1 mm-diameter tungsten anode that extended 1.6 cm beyond the cathode and was tapered to a point over 1 cm. Electrons emitted from the cathode are bent by their self magnetic field and subsequently pinch onto the tip of the anode producing a small, intense bremsstrahlung source. The generator (a 2-Ohm machine) was configured with parallel loads that carried the bulk of the available current during the pulse. Radiation from the parallel-load diodes was attenuated with lead shielding. In addition, specially designed resolution targets and two test objects were radiographed and their projected images analyzed to validate the source quality. The source size inferred from these images is consistent with the 1 mm spot size deduced from the more traditional and historic rolled-edge technique.