Ion pulse propagation through a previously unfilled electrostatic aperture lens accelerating column

Heavy ion fusion experiments require very high current beams with excellent beam quality during a short pulse. Scaled experiments planned at LBL require very short pulses (μsec) compared to what one expects in an HIF driver (20-30 μs). A 1 MV acceleration column composed of aperture lenses has been constructed at LBL in order to study the propagation effects on such ion pulses. The column is initially empty of space charge but with the full acceleration potential applied. A short current pulse is then injected into the column with a planar diode “current valve”. Effects on the pulse propagation due to rise time, pulse duration, and beam size have been studied. Experiments on transported beam current and emittance have been conducted using a carbon arc plasma source (2" and 5" diameter) and a 1" diameter potassium alumino-silicate ion source. Computer simulations using a 2.5D time dependent code are compared with the experimental data