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Description
Double-Null (DN) configurations are a leading candidate for future tokamak power exhaust management, yet the precise impact of the magnetic configuration on divertor asymmetry remains a critical challenge. This work employs SOLPS-ITER simulations with full drifts to investigate the interplay between triangularity ($\delta$) and transport in TCV L-mode DN discharges, focusing on the physics of detachment. The simulations reveal distinct roles for drift mechanisms in determining divertor asymmetry: $E \times B$ drifts are found to primarily drive in-out asymmetry, while diamagnetic drifts significantly contribute to the up-down asymmetry. Crucially, these drift effects are modulated by the presence of port protection tiles, which modify the effective divertor leg lengths and closure, thereby altering the power sharing and detachment access.Regarding detachment, defined as a target electron temperature ($T_e < 5$) eV, Negative Triangularity (NT) configurations are found to be inherently more difficult to detach than Positive Triangularity (PT). Simulations show that core density ramps alone fail to cool the NT outer target below this 5 eV threshold. This resistance to detachment is attributed to a combination of higher heat flux flowing to the Low Field Side (LFS), a physically shorter outer divertor leg which limits the power dissipation volume, and a narrower power fall-off length ($\lambda_q$) accompanied by a lower spreading factor ($S$). To mitigate these geometric and transport limitations, Nitrogen ($N_2$) seeding is investigated. The simulations demonstrate that $N_2$ seeding effectively accesses a high-radiation regime, enabling detachment at the outer target without the upstream profile degradation associated with pure density ramps. Finally, to strictly disentangle the fundamental effects of shaping from topological variations, a specific controlled case with matched divertor leg lengths and closure is analyzed; this confirms that triangularity intrinsically modifies the drift-driven transport patterns even when geometric parameters are fixed. These results indicate that realizing the benefits of DN in reactor designs like DEMO requires optimizing the magnetic shape to manage the specific coupling between triangularity-induced leg length variations and drift-driven plasma transport.