  Cold atom fountain clocks provide exceptional long term stability as they
increase interrogation time at the expense of a larger size. We present a
compact cold atom fountain using a grating magneto-optical trap (GMOT) to laser
cool and launch the atoms in a simplified optical setup. The fountain is
evaluated using coherent population trapping and demonstrates improved
single-shot stability from the launch. Ramsey times up to 100 ms were measured
with a corresponding fringe linewidth of 5 Hz. This technique could improve
both short- and long-term stability of cold atom clocks whilst remaining
compact for portable applications.
