Design options for the upgrade of the CMS electromagnetic calorimeter

The CMS scintillating lead-tungstate calorimeter was designed to operate for at least ten years at the LHC, assuming an instantaneous luminosity of $10^{34}$ cm$^{-2}$ s$^{-1}$. The measurements obtained with data collected in LHC Run1 (2010-2012) show that the detector has performed according to design specifications and will survive with excellent performance through the lifetime of the LHC. However, plans for an upgrade of the LHC (the High Luminosity LHC, HL-LHC, project) aim at accumulating a much higher integrated luminosity, up to 3000 fb$^{-1}$ in ten years. This will expose the detector to a total irradiation about six times higher with respect to the design specifications. An intense campaign of activities has started to define the improvements needed to survive such an increase in irradiation levels. The activities carried out include irradiation studies, simulations, design, realisation and test of prototypes of new detectors that may substitute the present one in the endcap regions. The options currently under study and the results obtained so far on the subjects outlined above will be presented.