  We present the results of experimental studies on the transverse and
longitudinal dynamics of a single electron in the IOTA storage ring. IOTA is a
flexible machine dedicated to beam physics experiments with electrons and
protons. A method was developed to reliably inject and circulate a controlled
number of electrons in the ring. A key beam diagnostic system is the set of
sensitive high-resolution digital cameras for the detection of synchrotron
light emitted by the electrons. With 60-130 electrons in the machine, we
measured beam lifetime and derived an absolute calibration of the optical
system. At exposure times of 0.5 s, the cameras were sensitive to individual
electrons. Camera images were used to reconstruct the time evolution of
oscillation amplitudes of a single electron in all 3 degrees of freedom. The
evolution of amplitudes directly showed the interplay between
synchrotron-radiation damping, quantum excitations, and scattering with the
residual gas. From the distribution of measured single-electron oscillation
amplitudes, we deduced transverse emittances, momentum spread, damping times,
and beam energy. Estimates of residual-gas density and composition were
calculated from the measured distributions of vertical scattering angles.
Combining scattering and lifetime data, we also provide an estimate of the
aperture of the ring. To our knowledge, this is the first time that the
dynamics of a single electron are tracked in all three dimensions with digital
cameras in a storage ring.
