Charged particle multiplicities in inelastic pp interactions with ATLAS and the ATLAS Minimum Bias Tune 1

Measurements of the charged particle multiplicity produced in proton-proton collisions at the LHC at centre-of-mass energies $sqrt{s}=0.9$~TeV and $7$~TeV recorded with the ATLAS detector are presented. Distributions are measured for events with at least one charged particle $n_{ch}geq1$ in the kinematic range $|eta|<2.5$ and $p_T>500$~MeV. The measurement is also constrained to a diffraction-limited phasespace $n_{ch} geq 6$ and used for the production of the first py6 tune to LHC data, the ATLAS Minimum Bias Tune~1 (AMBT1).