We will continue in from the previous segment of this topic, in which we introduced nuclear weapons themselves and took a look at fission bombs.
The other primary type of nuclear weapon is fusion bombs. Fusions bombs are generally referred to as thermonuclear weapons or hydrogen bombs. These bombs rely on fusion reactions between isotopes of hydrogen, deuterium and tritium. All such weapons require a significant portion and sometimes a majority of their energy from fission. This is because a fission reaction is required as a trigger for the fusion reaction, and from their fusion reaction can themselves trigger additional fission reactions.
Thermonuclear bombs work by using the energy of a fission bomb to compress and heat fusion fuel. When a fission bomb is detonated, gamma rays and e-rays emitted first compress the fusion fuel, then heat it to thermonuclear temperatures. Thus ensuring reaction creates enormous numbers of high-speed neutrons, which can then induce fission in materials that are not normally prone to it, such as depleted uranium.
Since fusion reactions do not create fission by products, thus they contribute far less to the creation of nuclear fallout than fission reactions, but because all thermonuclear weapons contain at lesson one fission stage, thermonuclear weapons can generate as least as much fallout as fission only weapons.
Boosted fission weapon
This is a fission bomb that increases its explosive yield through a small amount of fusion reactions, but it is not a fusion bomb. In a boosted bomb the neutrons produced by the fusion reaction serve primarily as a way to increase the efficiency of the fission bomb.
A neutron bomb is a thermonuclear weapon that yields a relatively small explosion but has a relatively large amount of neutron radiation, such a device could theoretically be used to cause massive casualties while leaving infrastructure mostly intact and creating a minimal amount of fallout. The detonation of any nuclear weapons is accompanied by a blast of neutron radiation.
This is a device that surrounds a nuclear weapon with suitable material such as cobalt or gold. These bombs can produce exceptionally large quantities of long-lived radioactive fallout. It has been theorised that such a device could serve as a doomsday weapon because such a large quantity of radioactive material with half-lives of decades, lifted into the stratosphere where wind currents would distribute it around the globe, would make all life on the planet extinct.