Antihydrogen, the bound state of a positron and an antiproton, is the simplest pure
anti-atomic system and an excellent candidate to test the symmetry between matter
and antimatter. This thesis focuses on the magnetic confinement of antihydrogen and
the first ever resonant interaction with trapped antihydrogen, as performed by the
The ALPHA apparatus and the techniques that have been developed to form,
trap, probe, and detect antihydrogen atoms will be described in detail. The first
successful demonstration of trapped antihydrogen will then be described. In the initial
demonstrations, 38 trapped antihydrogen atoms were detected after being confined
for at least 172 ms. Since then, over 400 antihydrogen atoms have been trapped and
confinement times of 1000 s (over 15 minutes) have been demonstrated.
Spectroscopy of these trapped antihydrogen atoms is the next major step forward.
As an initial proof-of-principle demonstration, ALPHA induced and observed
resonant positron spin flip (PSR) transitions between the ground states of antihydrogen.
Because of the strong magnetic field dependence of these transition frequencies, the
success of this experiment relied heavily on the ability to measure the magnetic field
seen by the antihydrogen atoms. A novel method to measure the magnetic field in situ
by detecting the cyclotron resonance of a trapped electron plasma is presented. This
method allowed ALPHA to measure the magnetic field strength at the minimum of
the magnetic antihydrogen trap to within 1.4 parts in 1000. Hardware improvements
and further study should allow this resolution to be improved by several orders of
magnitude. The cyclotron resonance measurements can also be applied as a rough
diagnostic of a microwave field within the ALPHA apparatus. This allowed for
important diagnostics of the microwave field used to excite the PSR transitions.
Finally, the experimental results demonstrating resonant PSR transitions in antihydrogen
are presented. This experiment is the first ever spectroscopic measurement of
antihydrogen and an important step towards future precision spectroscopy.