Influence of the cathode lengths on the electron pinching characteristics of a rod-pinch diode

Summary form only given. The rod-pinch diode is a coaxial pinched-beam diode with a small-diameter anode rod extending through and beyond the cathode plane, which provides a pulsed small-area high-yield bremsstrahlung X-ray source for radiography1"2. PIC (Particle - in-Cell) simulations are performed to investigate the influence of the cathode lengths on the pinching characteristics of the diode. It is shown that increasing the cathode lengths won\´t reduce the time for the diode to achieve strong pinching, inconsistent with the general understanding3. The SCL current, proportional to the cathode length, is derived without considerations of beams emitted from the cathode\´s upstream and downstream surfaces perpendicular to the symmetry axis of the diode, while much more electrons are emitted from them than from the cylindrical surface parallel to the symmetry axis. The simulation results also show that increasing the cathode lengths will reduce the axial dimension of the X-ray spot size produced. Experiments to verify the above conclusions are being performed.