IHEP (Protvino) 3×3 m<sup>2</sup> cosmic ray muon tomograph

Muon tomography, based on the measurement of multiple scattering of cosmic ray muons traversing a volume to be investigated, is an attractive technique for detecting hidden high-Z materials. A cosmic ray muon tomograph with sensitive volume of 3m × 3m × 2.5m has been constructed at IHEP (Protvino) and is under producing first data and results. The description and characteristics of the setup are presented. The tomograph is built of 30 mm drift tubes operating in trigger-less mode. Tubes are filled with an Ar-CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> mixture and can operate for about one year without refreshing of the gas-mixture. Specialized track reconstruction, tomographic reconstruction and visualization tools were developed. Image reconstruction examples are presented.