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

Abstract

Intense-heavy-ion-beam transport through an insulator beam guide for heavy ion fusion AIP Conf.The Laser Evaporation Ion Source ͑LEVIS͒ 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-II͒ ͓J. P. VanDevender and D. L. Cook, Science 232, 831 ͑1986͔͒ at Sandia National Laboratories. The source configuration consists of two laser pulses impinging on a heated ͑200°C͒ thin-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 using the LIBORS ͑laser ionization based on resonant saturation͒ ionization method. Small-scale experiments determined that this dual laser-based approach can produce a source plasma of adequate density and confinement for acceleration and transport. Hardware modifications were undertaken to correct problems of premature impedance collapse and lack of beam lithium seen on previous PBFA-II experiments. As much as 85 kJ of Li is measured at the beam focus, but the source may not have been operating in a fully active ͑i.e., preformed͒ manner. Focusing performance appears superior to a passive LiF ion source operated on PBFA-II with the same magnetic field topology.

Use of radial self-field geometry for intense pulsed ion beam generation above 6 MeV on Hermes III.

“…Total load currents reached 170 kA, with typical Rogowski levels indicating 30 kA of ion current. The configuration with 6 cm and 12 cm for anode and cathode diameters, respectively(6)(7)(8)(9)(10)(11)(12), produced the highest inferred voltage, compared to the 8-14 configuration. This is consistent with Eq.…”

“…Pulsed intense ion beams have been in development since the 1970s for a number of applications, among them materials processing [1][2][3], and beams as drivers for light ion fusion [4]. In the latter case, beam energies of 10 MeV and above were desired for maximizing energy delivered to an eventual fusion target [5,6]. For materials processing, energies < 1 MeV are typically used.…”

New lithium gas sorbent

“…Previously, Ag-Li films have already been used as a reservoir for Li atoms in laser sources of lithium ions for accelerators [20][21][22][23]. The focus of these studies was on the diagnostics of lithium plasma but not on the evaporation kinetics and the changes in the film, which accompany evaporation.…”

Development and testing of a lithium ion source and injector

“…Very high current has been demonstrated with vapor Li þ sources ionized by high-power lasers [4], generally at low repetition rate.…”