NEXT: NEW backgrounds and extrapolation to NEXT-100

The NEXT experiment aims at the sensitive search of the neutrino-less double beta decay of 136 ^{136} Xe at the LSC. A large-scale prototype of a high-pressure gas-Xenon electroluminescent TPC (NEW) is being operated since 2016, proving both the excellent energy resolution and the topological capabilities for background rejection. NEW is currently measuring the backgrounds for the ββ \beta\beta search. The internal 222 ^{222} Rn activity has being measured, yielding (37.5±2.3 (stat.)±5.9 (syst.)) (37.5\pm 2.3~\mathrm{(stat.)}\pm 5.9~\mathrm{(syst.)}) ~mBq/m3 ^3 . The Rn-induced electron background has been characterized allowing for the validation of the MC expectations. The corresponding extrapolation to the NEXT-100 detector demonstrates that Rn will not be a dominant background source. For an expected total background below 4×10−4 4\times10^{-4} ~counts~keV−1 ^{-1} ~kg−1 ^{-1} ~yr−1 ^{-1} , NEXT-100 will reach a sensitivity to the ββ0ν \beta\beta0\nu half-life of 6×1025 6\times10^{25} y after 3 years of data taking.