4. Advanced Sources of Highly Charged Ions

Abstract

This chapter discusses that most of the matter in the universe exists in high-temperature plasma environments that contain highly ionized ions. Collisional and radiative processes, involving highly ionized ions, play important roles in astrophysical environments and in laboratory plasmas for fusion-energy and X-ray laser research. It presents a “map of the universe,” indicating the relationship between electron density and temperature for different kinds of plasmas, both naturally occurring and manmade. To produce highly ionized ions in the laboratory, a significant investment of energy to remove the bound atomic electrons is required. It is evident that special measures must be taken to produce highly ionized ions for research. One method that has been employed for decades is to accelerate ions of modest charge to energies in the mega-electron volt range or higher, and then to pass them through a thin foil or gas target to collisionally strip them of their electrons. Another method involves directing such an energetic ion beam through a gas target in which slow, highly charged recoil ions are produced by multiple ionization in energetic collisions with these fast “hammer” ions. The slow recoil ions of the gas target species are accelerated and formed into a low-energy beam for use in experiments that do not require high ion intensities. The production of intense, highly charged ion beams at low kinetic energies requires a special ion source. The chapter discusses the operating principles and performances of several types of advanced highly charged ion sources that are currently employed in experimental physics research.