Not that I am aware of. The very difficulty of building a nuclear explosive device is about premature initiation. Even if there were designs which could make us

Not that I am aware of. The very difficulty of building a nuclear explosive device is about premature initiation. Even if there were designs which could make use of constant high-intensity compact neutron source (perhaps in the fusion stage?), just putting it inside the weapon would be quite dangerous. Still, compact neutron sources have their uses.