Charge-to-mass separation in a current coaxial lens

Abstract

We present results demonstrating the charge state separation of an ion beam in a purely cylindrical geometry using the azimuthal magnetic field of a straight conductor. This geometry, called a current coaxial lens, has advantages for the analysis of intense ion beams where it is important to minimize space charge blow-up of the beam due to loss of space charge neutralization. A metal vapor vacuum arc ion source was used to produce an annular, low energy, aluminum ion beam of total beam current several tens of milliamperes and with charge state components Q=1+, 2+, and 3+ at energies of 20, 40, and 60 keV, respectively. Separation of the three different charge state fractions of the beam was measured. The method has been shown to be effective for the case when the beam pulse is long compared to all ion transit times involved and the beam current is high in terms of the need for space charge neutralization.