What is swan device (nuclear primary)

 The "Swan device" in the context of nuclear weapons refers to a specific design of a nuclear primary, which is the first stage of a thermonuclear (hydrogen) bomb.¹ Here's a breakdown of what that means:

• Nuclear Primary: In a thermonuclear weapon, the primary stage is a smaller fission bomb.² When detonated, it produces the intense heat and radiation needed to compress and ignite the secondary stage, which contains thermonuclear fuel (like lithium deuteride).³ The primary essentially acts as the trigger for the much larger fusion explosion in the secondary.⁴
• Swan Design: The Swan was a boosted fission design developed in the United States.⁵ "Boosted" means that a small amount of deuterium-tritium gas is introduced into the core of the fission primary. When the fission reaction begins, the fusion of this gas releases a burst of high-energy neutrons, which significantly increases the efficiency of the fission reaction, leading to a higher yield for a given amount of fissile material.
• Key Characteristics of the Swan Primary:
  • It had an oblate spheroidal (rugby ball-like) shape.
  • It was relatively small and lightweight compared to earlier primaries. For example, one version had a diameter of about 22.4 inches and a length of 46.6 inches, weighing around 1225 lbs.⁶ The primary component itself was even smaller and lighter.
  • It was a highly successful and widely used design, serving as the primary for various US thermonuclear warheads.
  • The Dakota test in 1956 was an experiment of the Swan device as a nuclear primary.⁷ It was also used as the primary in the Redwing Mohawk shot later that year, which involved a thermonuclear device.⁸

In summary, the Swan device was a compact and efficient boosted fission primary design that was crucial for the development of more powerful and smaller thermonuclear weapons in the United States.⁹

It's important to note that the term "Swan device" in this context does not refer to a nuclear reactor or any safety mechanism within a nuclear facility. It is specifically related to the design of the primary stage of a nuclear weapon.