Resistive and ion-focused electron beam transport in capillaries

Pinched propagation of intense, pulsed electron beams occurs in two gas pressure regimes: a high pressure resistive regime and the low pressure ion focused regime (IFR). Although in most experiments, the transport tube radius aw is large compared with the beam radius ab´ beams can be efficiently transported in either regime even when aw/ab ≲ 3. Return currents in the tube wall provide a centering force which reduces the growth of transverse instabilities such as resistive hose or ion hose while correcting for minor aiming errors. The use of pinched transport eliminates the need for guide magnets. Analytical and simulation results show that it may be possible to transport high brightness, moderate power beams with ab ≪ 1 cm in narrow tubes or capillaries over distances of tens or hundreds of centimeters.