  The ArDM project aims at operating a large noble liquid detector to search
for direct evidence of Weakly Interacting Massive Particles (WIMP) as Dark
Matter in the universe. Background sources relevant to ton-scale liquid and
gaseous argon detectors, such as neutrons from detector components,
muon-induced neutrons and neutrons caused by radioactivity of rock, as well as
the internal $^{39}Ar$ background, are studied with simulations. These
background radiations are addressed with the design of an appropriate shielding
as well as with different background rejection potentialities. Among them the
project relies on event topology recognition, event localization, density
ionization discrimination and pulse shape discrimination. Background rates,
energy spectra, characteristics of the background-induced nuclear recoils in
liquid argon, as well as the shielding performance and rejection performance of
the detector are described.
