W66 (nuclear warhead)
The W66 thermonuclear warhead was used on the Sprint anti-ballistic missile system, designed to be a short-range interceptor to shoot down incoming ICBM warheads.
The W66 had a yield of 2 kilotonnes of TNT (8.4 TJ) and was an enhanced radiation ("neutron") weapon. The W66 was 18 inches (46 cm) in diameter and 35 inches (89 cm) long, with a weight of approximately 150 pounds (68 kg). The weapon was a two-stage design.
The W66 was based on the Arrow warhead design and by December 1966 had undergone six nuclear tests.