  In this paper, we study isometric actions on finite-dimensional CAT(0) spaces
for the Higman-Thompson groups $T_n$, which are generalizations of Thompson's
group $T$. It is known that every semi-simple action of $T$ on a complete
CAT(0) space of finite covering dimension has a global fixed point. After this
result, we show that every semi-simple action of $T_n$ on a complete CAT(0)
space of finite covering dimension has a global fixed point. In the proof, we
regard $T_n$ as ring groups of homeomorphisms of $S^1$ introduced by Kim,
Koberda and Lodha, and use general facts on these groups.
