A cusp field, hollow cathode, carbon cluster ion source

An all carbon hallow cathode ion source with a specially designed cusp magn etic field B-z(r, theta) is described. Velocity spectra from this source ha s shown that carbon cluster synthesis is taking place as a function of the source design, discharge parameters and the state of sooting. The cusp magn etic field seems to establish two distinct discharge regions within the sou rce. The first is a narrow annular ring that is 2 mm thick and 15-20 mm lon g with restricted axial and radial extent of the cusp field. Here the sourc e gas ionizes. The carbon atoms sputter off the cathode walls and subsequen tly get ionized. The other one is a cylindrical plasma region with the enti re axial range of B-z(r, theta). In this region the dynamics of the soot fo rmation from the plasma constituent on the cathode walls seems to be relate d to the carbon clustering processes. (C) 1999 Elsevier Science B.V. All ri ghts reserved.