  Ultra-high energy neutrinos are interesting messenger particles since, if
detected, they can transmit exclusive information about ultra-high energy
processes in the Universe. These particles, with energies above
$10^{16}\mathrm{eV}$, interact very rarely. Therefore, detectors that
instrument several gigatons of matter are needed to discover them. The ARA
detector is currently being constructed at South Pole. It is designed to use
the Askaryan effect, the emission of radio waves from neutrino-induced cascades
in the South Pole ice, to detect neutrino interactions at very high energies.
With antennas distributed among 37 widely-separated stations in the ice, such
interactions can be observed in a volume of several hundred cubic kilometers.
Currently 3 deep ARA stations are deployed in the ice of which two have been
taking data since the beginning of the year 2013. In this publication, the ARA
detector "as-built" and calibrations are described. Furthermore, the data
reduction methods used to distinguish the rare radio signals from overwhelming
backgrounds of thermal and anthropogenic origin are presented. Using data from
only two stations over a short exposure time of 10 months, a neutrino flux
limit of $3 \cdot 10^{-6} \mathrm{GeV} / (\mathrm{cm^2 \ s \ sr})$ is
calculated for a particle energy of 10^{18}eV, which offers promise for the
full ARA detector.
