Neptune-C pulsed electron beam

The Ion Physics Corporation Neptune-C Low Impedance Pulsed Electron Beam Generator, capable of several hundred kiloampere currents with mean energies from 100 to 500 keV in a power pulsewidth of approximately 70 nanoseconds, is described. Beam energies as high as 5 kilojoules in the anode plane and 2.3 kilojoules at the end of a solid guide cone in a drift chamber are possible. The pulse generator and diode characteristics for electron beam generation are discussed. Beam uniformity over 5 and 18 cm2 target areas were measured with a high resolution graphite calorimeter; measurements show the beam fluence is uniform over the central 0.8 inches of a 1.0 inch diameter beam. Maximum fluences delivered to a target at the end of a solid guide cone are 30 cal/cm2 over 18 cm2, 90 cal/cm2 over 5 cm2, and 150 cal/cm2 over 2.85 cm2. Shot-to-shot reproducibility at beam fluences from 26 to 68 cal/cm2 is better than +-7 percent. The energy deposition in a graphite target has been measured in a transmitted fluence experiment; the measured depth-dose profile agrees well with the calculated profile