Laser cooling of externally produced Mg ions in a Penning trap for sympathetic cooling of highly charged ions - Andelkovic, Z; Cazan, R; Noertershaeuser, W; Bharadia, S; Segal, DM; Thompson, RC; Joehren, R; Vollbrecht, J; Hannen, V; Vogel, M (PHYSICAL REVIEW A, 2013)