  Monte Carlo simulations show that the pulse profile of Cherenkov photons
measured near the core of an extensive air shower is sensitive to the secondary
muon/electron ratio of the cascade. Cherenkov pulses can easily be measured
with a single large area mirror viewed by a photomultiplier tube subtending a
small field of view (~1 degree). Even for such a simple experiment, exposed to
EAS from a range of core locations and arrival directions, strong statistical
differences are shown to exist between the pulse parameter distributions of
primary protons and those of heavier primary particles. A range of primary
energies can be investigated by varying the zenith angle of observations. In
this paper, results from simulations of primaries in the energy range 20TeV to
400TeV are presented, although in principle the technique could be extended to
include the knee of the spectrum. At the lower end of this energy range results
can be compared to direct measurements of the composition, while measurements
at the upper end can augment results from existing ground based experiments.
