Application of material budget imaging for the design of the ATLAS ITk strip detector

The technique of material budget imaging (MBI) allows to experimentally assess the material budget E = x/X0 of a material with thickness x and its radiation length X0. Here, multi-GeV electrons from a test beam facility such as the DESY-II test beam are used. This novel technique exploits the fact that the beam particles are deflected by multiple Coulomb scattering following a distribution of the deflection angle with a center at zero and a width depending on the traversed material. By reconstructing the individual kink angles from the measured particle trajectories in a high resolution beam telescope, the material budget can be extracted by applying appropriate models of multiple scattering theory, such as the Highland formula.On the one hand, various materials with known material budgets were measured to calibrate the MBI technique and study also different systematic effects such as the beam telescope's acceptance and the variation of the beam energy. On the other hand, a number of material samples planned in the design of the local support structures of the new ATLAS Inner Tracker (ITk) strip detector were investigated to extract the according radiation length values not known beforehand. This paper shows therefore the potential of the MBI technique to give an input for the design of high-energy particle detectors by providing experimentally measured numbers of the radiation length for various material compounds with not a-priori known X0 values.

Automated summary

The technique of material budget imaging (MBI) allows for experimental assessment of a material's material budget E = x/X0. The technique exploits the deflection of beam particles due to multiple Coulomb scattering to extract the material budget by reconstructing the individual kink angles from measured particle trajectories. This technique has been used to calibrate known material budgets and extract unknown radiation length values for the design of high-energy particle detectors.