"It's sort of a mini-hydrogen bomb," says Weapons Analyst Samuel T. Cohen of the so-called neutron bomb. Cohen should know. In the late 1950s, as a Rand Corp. consultant to the Air Force, he was the first to draw the military's attention to the possibility of making a new type of nuclear weapon. It would do the bulk of its damage not by heat or concussive force, but by a flood of high-energy subatomic particles called neutrons. Cohen, who has no academic credentials beyond a bachelor's degree from U.C.L.A., wanted to create a relatively "clean weapon" that produced a minimum of radioactive fallout, blast and heat.
In retrospect, it is easy to see why Cohen and his colleagues were fascinated by such a device. At the time, there was a growing revulsion against contamination by radioactive debris from extremely "dirty" nuclear tests in the atmosphere. Also, a low-yield bomb fitted in neatly with the limited-war concepts that were then being explored by the Eisenhower Administration. Some Pentagon strategists wanted to include in their nuclear arsenal a relatively small weapon that could be used tactically by troops in the field against a potential aggressor without causing incalculable havoc among civilian populations.
All nuclear weapons, of course, kill by heat, concussive force and radiation. But when their yield is reduced, as in the neutron bomb, the balance changes. In the words of Herbert Scoville Jr., a former weapons specialist for the Pentagon and CIA: "The instantaneous nuclear radiation, first gamma rays, then neutrons, become predominant, and the blast thermal effects become less and less important." As a result, if a typical bomb of this sort is exploded 500 ft. above the target, the blast and heat effects extend only about 400 yds. from ground zero, but the high-energy neutrons, hurtling in all directions and penetrating even the thick armor of tanks and other vehicles, can kill at distances of up to a mile. Victims of radiation sickness suffer from vomiting, fever, hemorrhaging and convulsions. Yet proponents of the bomb argue that because the radiation is short-lived and there is little lingering fallout, much of the battle zone remains fit for habitation and even people who live relatively close by should be safe if they have taken cover.
The construction details of the "neut" remain a guarded secret, but the principles are well known to physicists. Neutron bombs are essentially small thermonuclear devices, or H-bombs, the explosive equivalent of about 1,000 tons of TNT. Unlike the earliest A-bombs, which involved the fission—or splitting—of such radioactive materials as uranium and plutonium, H-bombs work by fusing isotopes of the simplest and lightest element, hydrogen, into slightly heavier atoms of helium, although they still require a small fission "trigger" to reach the sunlike temperatures (tens of millions of degrees) required for fusion.