I'm currently studying ion trap experiments, many papers suggest the cooling of trapped ions, and other papers say its a heating process. I know there's a difference as to what each refers but am unclear of the difference. I'll quote: http://iontrap.umd.edu/wp-content/uploads/2013/10/Thesis_2006_Deslauries.pdf Please could someone shed some light on how heating and cooling differ in this statement? What is heated, what is cooled? do both occur at the same time? Thanks for any ideas.