CERN Accelerating science

Article
Title	Characterization of a Tubular Hot-Cavity Surface Ionization Source
Author(s)	Liu, Yuan ; Bilheux, Hassina Z ; Kawai, Yoko
Affiliation	(ORNL, Oak Ridge, Tennessee)
Publication	2005
In:	21st IEEE Particle Accelerator Conference, Knoxville, TN, USA, 16 - 20 May 2005, pp.1581
Subject category	Accelerators and Storage Rings
Abstract	Elements with low ionization potentials can be efficiently ionized by positive surface ionization. It has been experimentally observed and theoretically shown that the ionization efficiency in a hot-cavity can be significantly higher than expected for the surface ionization mechanism. This is explained by the existence of a thermal plasma inside the cavity consisting of surface ionized ions and thermionic electrons. We have investigated the suggested ioniation mechanisms in a tubular hot-cavity surface ionization source where the area of the exit aperture is small compared with the tube inner surface. Thermal analyses of the tubular cavity and calculated mean number of wall collisions of a neutral particle in the cavity before escaping through the exit aperture are presented. Measured emittance and ionization efficiencies of various elements as a function of the cavity temperature for different cavity materials are discussed.