Modern third-generation synchrotron radiation facilities provide micro-focus beams of very high brilliance, with cross sections in the sub-micrometer range, beams of almost complete circular or linear polarisation, and beams with a signiﬁcant degree of coherence.
TESLA Technical Design Report Part I: Executive Summary
Usually the trapping potential is such that the ions are held in a linear array (Fig. 3.2), spaced apart by several micrometers due to the ion-ion Coulomb repulsion.
Experimental Quantum Computation with Nuclear Spins in Liquid Solution