  In the Collider Run II, the Tevatron operates with 36 high intensity bunches
of 980 GeV protons and antiprotons. Particles not captured by the Tevatron RF
system pose a threat to quench the superconducting magnet during acceleration
or at beam abort. We describe the main mechanisms for the origination of this
uncaptured beam, and present measurements of its main parameters by means of a
newly developed diagnostics system. The Tevatron Electron Lens is effectively
used in the Collider Run II operation to remove uncaptured beam and keep its
intensity in the abort gaps at a safe level.
