Cooling by spontaneous decay of highly excited antihydrogen atoms in magnetic traps

An efficient cooling mechanism of magnetically trapped, highly excited antihydrogen ((H) over bar) atoms is presented. This cooling, in addition to the expected evaporative cooling, results in trapping of a large number of (H) over bar atoms in the ground state. It is found that the final fraction of trapped atoms is insensitive to the initial distribution of (H) over bar magnetic quantum numbers. Expressions are derived for the cooling efficiency, demonstrating that magnetic quadrupole (cusp) traps provide stronger cooling than higher order magnetic multipoles. The final temperature of (H) over bar confined in a cusp trap is shown to depend as similar to 2.2T(n0)n(0)(-2/3) on the initial Rydberg level n(0) and temperature T-n0.