Radiation length measurements with high-resolution telescopes

The radiation length imaging method presented in this work can be used to conduct spatially resolved measurements of scattering angles of particles traversing a object under study. For the measurements a planar object is centred in a high-resolution telescope and the whole setup is positioned in a multi-GeV particle beam. The scattering angle distributions depend on the radiation length $X$/$X_0$ of the traversed object. Combining the radiation length information with the reconstructed intersections provides the opportunity to generate 2D images of the measurement objects material profile. Measured radiation length images of detector planes can be compared to existing detector models for validation and, when necessary, improvement of the detector simulation. In order to demonstrate the capabilities and scope of the X/X0 imaging method, several beam tests have been conducted in the last years. The imaged objects varied from a ultra thin vertex detector ladder designed for the Belle II experiment to a prototype module for the ATLAS ITk upgrade. Additionally a series of measurements were conducted to determine the radiation length constant $X_0$ of hardened conductive glues. To test systematic effects, such as energy loss due to bremsstrahlung, measurements on copper and aluminium wedges with a continuously increasing radiation length were conducted.