Efficient injection of electron beams into magnetic guide fields

Propagation of pulsed electron beams in grad B channels has been studied extensively theoretically and experimentally as a method for guiding such beams at high energy densities onto a converter target to generate intense bremsstrahlung radiation. A key problem in making this approach practical is the efficient injection of the beam from the diode into the drift tube. A method for achieving nearly 100% injection from the diode into the drift channel was developed at Kharkiv State University (KhSU) for 50 kA beams. This method uses an injection of the beam from a ring diode into the grad B drift tube with an appropriate transition of the magnetic field from the diode into the drift tube. Scaling experiments have been performed at up to 100 kA level at KhSU and are being extended to >500 kA level on Gamble II generator at the Naval Research Laboratory.