Perpendicular laser cooling with a rotating wall potential in a Penning   trap
  We investigate the impact of a rotating wall potential on perpendicular laser cooling in a Penning ion trap. By including energy exchange with the rotating wall, we extend previous Doppler laser cooling theory and show that low perpendicular temperatures are more readily achieved with a rotating wall than without. Detailed numerical studies determine optimal operating parameters for producing low temperature, stable 2-dimensional crystals, important for quantum information processing experiments employing Penning traps. 
Steven B. Torrisi, Joseph W. Britton, Justin G. Bohnet, and John J.   Bollinger
quant-ph physics.atom-ph physics.plasm-ph