  We introduce a new simplified method for computing the electron field
emission current in short carbon nanotubes using ab-initio computation in
periodic simulation cells. We computed the evolution of the wave functions
using Time-Dependent Density Functional Theory, where we have utilized the
Crank-Nicholson propagator. We found that in pristine carbon nanotubes, the
emitted charge tends to emerge mostly from electrons that are concentrated at
the nanotube tip region. The charge beam concentrates into specific channel
structures, showing the utility of carbon nanotubes in precision emission
applications.
