9. Let $f(x)$ be an odd function defined on $\mathbf{R}$. If for any real number $x$, $f(x+2)=-f(x)$, and when $x \in[0,1]$, $f(x)=2 x$, then $f(10 \sqrt{3})=$ $\qquad$ .
$$
f(x+2)=-f(x)=f(-x) \Rightarrow f(2-x)=f(x) \text { and } f(x+4)=f(x) \text {, }
$$

then $f(10 \sqrt{3})=f(10 \sqrt{3}-16)=f(18-10 \sqrt{3})=36-20 \sqrt{3}$.