Supersymmetric scale-separated AdS$_3$ orientifold vacua of type IIB

I construct supersymmetric AdS$_3$ vacua of type IIB string theory that exhibit parametric scale separation in the controlled regime. These solutions arise from compactifications on seven-dimensional manifolds equipped with co-closed $G_2$-structures, in the presence of orientifold planes preserving minimal supersymmetry. I focus on $\mathbb{Z}_2^3$ orbifolds of a specific solvmanifold and all seven-dimensional nilmanifolds, each requiring distinct configurations of intersecting O5-planes, which are treated in the smeared approximation. Weak string coupling and large volumes can be achieved for classical backgrounds on both nilmanifolds and solvmanifolds by tuning unbounded fluxes to large values. This achieves scale separation in the nilmanifold case, but the same cannot be concluded for the solvmanifolds. Furthermore, for some solutions, the holographic field theory operators dual to the lightest scalar fields have integer conformal dimensions at tree level, as in other scale-separated type IIA orientifold backgrounds.