Internal alignment and position resolution of the silicon tracker of DAMPE determined with orbit data

The DArk Matter Particle Explorer (DAMPE) is a space-borne particle detector designed to probe electrons and gamma-rays in the energy range from few GeV to 10 TeV, as well as proton and nuclei components of cosmic rays in the energy range from 10 GeV to 100 TeV. The Silicon-Tungsten tracKer-converter (STK) is a crucial component of DAMPE. It allows to estimate the direction of incoming photons converting into electron-positron pairs and identify the trajectories and the charge (Z) of cosmic ray particles. The STK consists of 768 silicon microstrip sensors assembled in 6 double layers with a total active area of 6.6 $mathrm{m}^2$. Silicon planes are interleaved with three layers of tungsten plates, resulting in about one radiation length of material in the tracker. The internal alignment parameters of the tracker have been determined on orbit, with non-showering protons and helium ions. We describe the alignment procedure and present the results for the position resolution and alignment stability. The position resolution after applying the alignment procedure is better than 50 $mathrm{mu m}$ for all the particle incidence angles.