Askaryan Radio Array (ARA) is being built at the South Pole aiming
for observing high energy cosmogenic neutrinos above 10 PeV.
The ARA detector identifies the radio emissions from the excess
charge in a particle shower induced by a neutrino interaction. Such
a radio emission was first predicted by Askaryan in 1962 and
experimentally confirmed by Saltzberg et al. using the SLAC accelerator
in 2000. We also performed a similar experiment using 40 MeV electron
beams of the Telescope Array Electron Light Source, aiming to verify
our understanding of the Askaryan emission and the detector responses
used in the ARA experiment. Clear coherent polarized radio signals were
observed with an ice target. On the other hand, clear signals were also
observed without any target due to the sudden appearance of the beam.
We performed a detailed simulation to understand our data. The final
results of the experiment will be presented in the conference.