Two point charges $-Q$ and $+Q / \sqrt{3}$ are placed in the $x y$-plane at the origin $(0,0)$ and a point $(2,0)$, respectively, as shown in the figure. This results in an equipotential circle of radius R and potential $\mathrm{V}=0$ in the xy -plane with its center at $(\mathrm{b}, 0)$. All lengths are measured in meters.

The value of B is ___ meter