Trapping antimatter
Charged antiparticles such as positrons and antiprotons can be trapped easily using Penning traps, such as this one from the ATRAP experiment (top). Antihydrogen atoms, on the other hand, are neutral and therefore escape the trap and annihilate with ordinary matter. To confine anti-atoms, we need to surround the Penning trap electrodes (yellow in both figures) with additional magnetic fields, which act on the dipole moments of the atoms and cause those in certain states to seek the field minimum at the trap centre. The necessary field configuration can be obtained by adding a transverse multipole winding (quadrupole shown) and longitudinal "mirror" coils around the Penning trap (arrows denote the direction of current in the coils). The challenge is to do this without disturbing the confinement of the charged antiprotons and positrons.