A source for producing alkali ion beams for low-energy surface scattering spectroscopies

Publisher Website
Google Scholar
Abstract
We present the design and performance of an alkali ion source which is the injection stage of an ion beam system for surface scattering experiments in the range of 10 eV to 10 keV. In order to maximize emitter lifetimes, emphasis was placed on obtaining low phase space beams which minimize current losses in later stages of the optics. The source is based on a commercially available solid state β‐eucryptite emitter, uses two stages of extraction for independent control of extracted current and final beam energy, and has a modified Pierce confinement electrode to control space charge spreading inside the source. Results of computer ray tracing are included to illustrate the operation of this source. Tests with K+ ions at 500 eV have produced beams which, in the range of 600–700 nA, were space‐charge limited in transport through the remainder of the system. Beam currents measured more than 1 m downstream of the source are nearly independent of the emitter surface temperature over a range of 1023 to 1142 °C. Emitter lifetimes in excess of 200 h have been obtained. Using this source and our beamline optics, we have produced at the sample position low phase space beams ranging in energy from 10 eV to several kiloelectron volts.

This publication has 9 references indexed in Scilit: