I'm not sure that is the case. "Any economic unit can emit money. The serious problem is to get it accepted" Hyman Minsky
Later devices have relied on some form of explosive compression of a subcritical lump which is assumed to be a necessary technology to build miniaturised weapons.
However take this all with a grain of salt because I'm not a physicist with any real expertise in building these things, and much of the information in public literature is probably misleading. Any idiot can face a crisis - it's day to day living that wears you out.
But what do I know, I didn't even read the book, just saw Pierce Brosnan playing the Russian agent in the movie. Oye, vatos, dees English sink todos mi ships, chinga sus madres, so escuche: el fleet es ahora refloated, OK? — The War Nerd