Silicon and Silicone are completely different stuffs. One’s the element, the other one is the rubber. And I don’t remember reading anything in the patent application about them as coolants. They are both not useful here anyway. Both consisting of Si (Silicon) with an atomic number of 14, so pretty opaque to x-rays.
Lithium on the other hand melts at 180° and boils at 1342°C. With Decaborane melting at 99°C and boiling at 213°C, that makes Lithium a pretty good candidate. Also with its 3 protons, that’s pretty much invisible to x-rays – even better than the surrounding Beryllium.
