Radiation Levels and Saturation Effects in the Electromagnetic Calorimeter of Future Linear Colliders

For the design of the electromagnetic calorimeter (ECal) of a future linear collider the required dynamic range for the possible readout options and the expected radiation doses have to be known. High energy electromagnetic showers are simulated to estimate the required dynamic range for a scintillator-pad based ECal read out with silicon photo-multipliers. For 1.5\,TeV photons energy deposits corresponding to $10^4$ and more minimum ionising particles in pads of 10\,mm × 10\,mm and 20\,mm × 20\,mm are found. From simulations of the main beam-induced backgrounds a maximal total ionising dose of a few Gray per year and 1-MeV-neutron equivalent fluxes around $10^{10}$ per square centimetre and year are found in the ECal of the 3 TeV CLIC and 1 TeV ILC experiments.