CHATBOT: It seems like the weapon you're referring to is a "neutron bomb" or an "enhanced radiation weapon" (ERW). It is a type of nuclear weapon with a lower explosive yield, but it releases a larger amount of neutron radiation. This type of weapon is designed to cause significant damage to living organisms through radiation exposure, while creating minimal blast damage to infrastructure. The description you provided is somewhat accurate. A neutron bomb's radiation can penetrate various materials, including bunker walls. The extent to which it can penetrate depends on the thickness and composition of the material. While it may not entirely destroy the bunker or its surrounding infrastructure, the radiation can still harm or kill living organisms inside. However, it's important to note that this type of weapon isn't a "free-neutrons based weapon" but rather releases high amounts of neutron radiation on detonation.

CHATBOT: Creating a neutron gun as a handheld weapon would face significant scientific and engineering challenges. While it might be theoretically possible, it would require major advancements in our understanding of particle physics and a significant reduction in the size and weight of equipment needed to generate and control neutron radiation. There's also the issue of heavy shielding to protect the shooter from radiation exposure. In the context of a sci-fi book, you might want to consider alternatives that are more plausible but still have a similar effect. One option could be a high-energy particle beam weapon that fires focused beams of subatomic particles, like protons or electrons, at high speeds. These particles could potentially penetrate various materials and cause damage to living organisms. Another option could be a weapon that uses a highly advanced, tunable X-ray or gamma-ray laser to penetrate different types of materials and harm targets behind them. Both alternatives would still require significant advancements in technology and pose safety challenges for the user, but they offer a more conceivable basis for a futuristic weapon than a handheld neutron gun. Keep in mind that in the context of a sci-fi book, some creative liberties can be taken with the explanation and functionality for the sake of the story.