Preliminary Background Model for LEGEND-1000

The Large Enriched Germanium Experiment for Neutrinoless double-beta Decay (LEGEND) aims to develop a phased $^{76}Ge$-based neutrinoless double beta ($0\nu\beta\beta$) decay experimental program with a discovery potential at a half-life beyond $10^{28}$ years. The final phase of the experiment, LEGEND-1000, will house 1 ton of HPGe detectors enriched with $^{76}Ge$ to provide a total exposure of 10 ton.yr. To achieve our discovery sensitivity goal, the detectors need to be operated in a nearly background-free regime enabled by a background index of less than $1 \times 10^{-5}$ cts/keV.kg.yr near the end-point energy $Q_{\beta\beta}$ (2039 keV). Numerous background suppression techniques have been implemented. These techniques include the use of large inverted-coaxial point-contact (ICPC) detectors with excellent energy resolution and pulse-shape discrimination capability, ultra-radiopure and low-mass components to minimize nearby radioactive contaminates as the active liquid-argon veto to reject backgrounds. In this talk, I will discuss in detail each of the techniques used for modeling the backgrounds for LEGEND-1000.