  Air-shower measurements in the primary energy range beyond 10 TeV can be used
to address important questions of astroparticle and particle physics. The most
prominent among these questions are the search for the origin of charged
Galactic cosmic rays and the so-far little understood transition from Galactic
to extra-galactic cosmic rays. A very promising avenue towards answering these
fundamental questions is the construction of an air-shower detector with
sufficient sensitivity for gamma-rays to identify the accelerators and large
exposure to achieve accurate spectroscopy of local cosmic rays. With the new
ground-based large-area (up to 100 square-km) wide-angle (Omega ~ 0.6-0.85 sr)
air-shower detector concept HiSCORE (Hundred*i Square-km Cosmic ORigin
Explorer), we aim at exploring the cosmic ray and gamma-ray sky
(accelerator-sky) in the energy range from few 10s of TeV to 1 EeV using the
non-imaging air-Cherenkov detection technique. The full detector simulation is
presented here. The resulting sensitivity of a HiSCORE-type detector to
gamma-rays will extend the energy range so far accessed by other experiments
beyond energies of 50 - 100 TeV, thereby opening up the ultra high energy
gamma-ray (UHE gamma-rays, E > 10 TeV) observation window.
