Muon tomography with a detector test facility

Cosmic muons are well suited for the calibration of gaseous detectors used for the tracking of minimum ionizing particles. The LMU cosmic ray facility in Garching, built for the calibration of Monitored Drift Tube (MDT) chambers for the ATLAS muon spectrometer, is meanwhile used to calibrate large area micropattern detectors. Two reference MDT chambers are sandwiching the detector under investigation. The track prediction of both MDT chambers is then compared to the hit position reconstructed by the detector under investigation. Using muon entrance angles between 0 ^circle and 30 ^circle allows for the detection of deviations in the detector geometry from design values in 3D. In this talk the capability of the cosmic ray facility to detect multiple scattering is used for muon tomography. Geometrical properties and positions of material between the two MDT chambers can be detected by the reconstruction of the cosmic muon track in both detectors. The intersection of both tracks, when having a relative angle close to the multiple scattering prediction, allows to reconstruct complex objects. This is demonstrated on the example of a large area Micromegas detector being under investigation between the two reference chambers.