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Description
The radiation hardness of 3D pixel sensors with small pixel sizes of 50x50 and 25x100 µm² produced by CNM Barcelona is tested up to HL-LHC fluences. Since a readout chip with the desired pixel size is still under development by the RD53 collaboration, first prototype small-pitch pixel sensors were designed to be matched to the existing ATLAS IBL FE-I4 readout chip for testing. Irradiation campaigns with such pixel devices have been carried out at KIT with a uniform irradiation of 23 MeV protons to a fluence of 5$\times10^{15}\,n_{eq}$/cm$^2$, as well as at CERN-PS with a non-uniform irradiation of 23 GeV protons to a peak fluence of 1.4$\times10^{16}\,n_{eq}$/cm$^2$. The hit efficiency has been measured in several beam tests at the CERN-SPS in 2016. The benchmark efficiency of 97% has been reached at remarkably low bias voltages of 40 V at 5$\times10^{15}\,n_{eq}$/cm$^2$ or 100 V at 1.4$\times10^{16}\,n_{eq}$/cm$^2$. Thanks to the low operation voltage, the power dissipation can be kept at low levels of 1.5 mW/cm² at 5$\times10^{15}\,n_{eq}$/cm$^2$ and 13 mW/cm² at 1.4$\times10^{16}\,n_{eq}$/cm$^2$ for -25$^{\circ}$C.
