Laser cooled ions in a Penning trap can be isolated from the environment by placing them
in vacuum and only interacting with them through optical and RF fields. The number
of trapped particles can be varied from a single ion up to thousands. Confinement is
provided by a static homogeneous magnetic field and a quadrupole electric potential. In
the natural frame of the ions, this appears as a 3D simple harmonic potential. Therefore
three dimensional structures can be formed in the absence of any additional RF field which
may lead to heating as is the case with RF traps. There are 3N different motional modes
for N particles. I present an analysis of the motion of a single particle showing that the
energy levels for all three modes are equally spaced. I also describe the interaction between
a trapped two level atom and an optical field.
During my time in the lab the laser and computer control of the experiment has been
significantly improved. In addition, an existing trap was modified to provide greater optical
access and fluorescence collection. This allowed the vibrational levels superimposed on
the internal states of a single 40Ca+ ion to be resolved via a narrow linewidth, electric
quadrupole transition. This is the first observation of magnetron and modified cyclotron
sidebands on an optical transition.
When more than one calcium ion is laser cooled, and their temperature reduced below
5mK, they form a Coulomb crystal. The locations of the ions minimise the total potential
energy which is comprised of the Coulomb repulsion and trap potential. The fluorescence
collection optics have been arranged to resolve individual ions in these crystals. Information about the motion of the ions is deduced by comparing photos from the experiment to
numerical simulations. Previously, only two ions have ever been aligned along the magnetic field in a Penning trap. I present strings of up to 29 particles and suggest the only
limitation, apart from the electrode structure, is the overlap of the laser beams with the
ions.