“…Subsequent developments employed the principles of nonuniform and time-varying electric fields to trap particles using a wide variety of electrode configurations, including hyperboloidal endcaps above and below a hyperbolic ring (Wuerker et al, 1959a;Davis and Ray, 1980), spherical end electrodes inside a cylinder (Berg et al, 1970), spherical-void electrodes (Arnold and Folan, 1987), and ring-shaped electrodes in various arrangements (Berg et al, 1970;Weiss-Wrana, 1983;Davis et al, 1990;Ray et al, 1991). Of special interest to the evolution of our system is the cubic design developed initiafly by Wuerker et al (1959b) and later by Zaritskii et al (1971). Separate alternating (AC) voltages from a three-phase power supply were applied to the three pairs of opposing faces of the cell.…”