Antihydrogen Synthesis & Trapping

2. Trapping of Antihydrogen

Antihydrogen is electrically neutral, so it cannot be confined with the combination of electric and magnetic fields that confine the charged positrons and antiprotons. Antihydrogen does however have a magnetic "dipole moment", which means that it can be confined using an arrangement of magnetic fields. The dipole moment is a very small quantity, so strong magnetic fields are required.

Cold antihydrogen is a prerequisite for trapping it. However, as no efficient way exists to cool antihydrogen after formation, the antihydrogen must actually not only be formed cold, but also be formed in the trap. So to trap it, the process below takes place in a magnetic trap for antihydrogen. The magnetic trap is formed by two axially separated co-axial coils and a transverse octupole magnet. All are superconducting to allow for fields up to about 2 Tesla. The atom can be trapped in this configuration due to its small magnetic moment, mostly stemming from the positron magnetic moment (positrons act like tiny bar magnets). The combination of the above magnets allow a three dimensional minimum in magnetic field strength to be formed that can trap (anti-)atoms. The video shows the trapping magnets and a 2D illustration of the 3D magnetic potential that the atom “sees”.