Development of the laser evaporation ion source for lithium beam generation on the Particle Beam Fusion Accelerator (PBFA-II)

The Laser Evaporation Ion Source (LEVIS) active lithium ion source has been developed for use on the focusing ion diode operated on the 10 TW Particle Beam Fusion Accelerator-II (PBFA-II) [J. P. VanDevender and D. L. Cook, Sc ience 232, 831 (1986)] at Sandia National Laboratories. The source configur ation consists of two laser pulses impinging on a heated (200 degrees C) th in-film LiAg layer on the anode surface. A short-pulse Nd:YAG laser creates a high-density vapor, which is then ionized by a long-pulse dye laser usin g the LIBORS (laser ionization based on resonant saturation) ionization met hod. Small-scale experiments determined that this dual laser-based approach can produce a source plasma of adequate density and confinement for accele ration and transport. Hardware modifications were undertaken to correct pro blems of premature impedance collapse and lack of beam lithium seen on prev ious PBFA-II experiments. As much as 85 kJ of Li is measured at the beam fo cus, but the source may not have been operating in a fully active (i.e., pr eformed) manner. Focusing performance appears superior to a passive LiF ion source operated on PBFA-II with the same magnetic field topology. (C) 1999 American Institute of Physics. [S1070-664X(99)02409-X].