Transverse emittance studies of an induction accelerator of heavy ions

Experiments conducted on MBE-4, a four-beam Cs/sup +/ induction linac, are discussed. The space-charge dominated beams of MBE-4 are focused by electrostatic quadrupoles while they are accelerated from nominally 200 keV up to approximately 1 MeV by 24 accelerating gaps. Initially the beams have currents of typically 4 mA to 10 mA per beam. Early experimental results showed a growth of the normalized emittance by a factor of 2 while the beam current was amplified by up to nine times its initial value. The results of recent experiments are discussed in which a mild bunch length compression rate, more typical of that required by a fusion driver, has shown that the normalized emittance can be maintained at its injection value (0.03 mm-mr) during acceleration.<>