We have investigated motional heating of laser-cooled 9Be+ ions held in
radio-frequency (Paul) traps. We have measured heating rates in a variety of
traps with different geometries, electrode materials, and characteristic sizes.
The results show that heating is due to electric-field noise from the trap
electrodes which exerts a stochastic fluctuating force on the ion. The scaling
of the heating rate with trap size is much stronger than that expected from a
spatially uniform noise source on the electrodes (such as Johnson noise from
external circuits), indicating that a microscopic uncorrelated noise source on
the electrodes (such as fluctuating patch-potential fields) is a more likely
candidate for the source of heating.Comment: With minor changes. 24 pages, including 7 figures. Submitted by Phys.
Rev.
