Lithium ion beam experiments on PBFA II

Summary form only given, as follows. Experiments are underway on the applied-B ion diode in Sandia´s Particle Beam Fusion Accelerator II (PBFA II) with the goal of generating and focusing intense lithium ion beams. Several lithium ion sources, including field-enhanced solid LiF, liquid lithium nitrate, and liquid Li are under investigation. With PBFA II operating at half-energy, 9.2 TW of power and over 300 kJ of energy have been coupled into ions from the LiF source, with an 87% ion current efficiency. However, bringing an Li/sup +/ beam to focus in the diode requires attention to a number of problems. First, the B-field topology required to focus lithium is quite different from the topology required to focus protons. Second, at low energies, energy loss and small-angle scattering in the gas-cell foil and in the neutralizing gas itself significantly affect beam transport efficiency. Third, nonuniformities in the diode magnetic field and the effects of the time-dependent self-magnetic-field of the ion beam must be compensated for. In the initial experiments, these problems prevented all but about 1% of the ion beam from reaching the diode axis.<>