The Past

From 1943 to today

Scientists and support personnel from around the world began their work at Los Alamos National Laboratory—then dubbed Project Y—in 1943.

With the development of high-energy explosives came the need for detonators—small devices used to set off explosives. These detonators had two critical functions: to initiate an explosion and to do so at the right time. An ill-timed detonator could have dire consequences.

The Past

With the development of high-energy explosives came the need for detonators—small devices used to set off explosives. These detonators had two critical functions: to initiate an explosion and to do so at the right time. An ill-timed detonator could have dire consequences.

Scientists and support personnel from around the world began their work at Los Alamos National Laboratory—then dubbed Project Y—in 1943. While some Laboratory scientists developed a plutonium core for the first atomic bomb, others designed a new kind of detonator to ensure the bomb would actually explode. The plutonium core, or pit, required the charges surrounding it to detonate almost instantaneously. Because any delay could cause failure, the Lab’s South Mesa Detonator Group designed and experimented with device variations until they developed the world’s first exploding bridgewire (EBW) detonator—the safest, highest performing, and most reliable detonator yet.

Existing detonation technology relied on electricity to heat a bridgewire, like the filament in a light bulb, until it ignited. However, that was too slow for a nuclear weapon—nearly 10,000 times slower than the EBW that the Detonator Group created. Physicists Luis Alvarez and Lawrence Johnston found that with the right material and size of bridgewire, they could deliver a rapid jolt of high voltage that forced a reaction. The jolt vaporized the wire, created an arc, and then initiated a phase change from solid to plasma that created a shockwave—all in a tenth of a microsecond.

With the skill of an artist and the eye of a scientist, South Mesa Detonator Group personnel brought these EBWs to life, one by one. From the outside, the EBW looked like a metal cylinder, about half the size of a soda can, with two horns that protruded horizontally. Inside each horn, Laboratory workers had placed a gold bridgewire the diameter of a single strand of hair. Cables supplying the heavy current of electricity were fitted to each horn. This detonator design was critical to the safety of the bomb because an EBW requires a specific energy source to set it off, reducing the possibility of an accidental explosion and making it much safer than any detonator in the world. Because the bridgewires were so thin, detonator assembly required great attention to detail and the use of small, dexterous hands. Often, it was women who assembled these EBWs.

The South Mesa Detonator Group manufactured all the EBWs that would be used in the Gadget, the first nuclear test. Thirty-two of these detonators would eventually be placed in Fat Man, one of the Laboratory-developed atomic bombs that helped end World War II.

As the Atomic Era continued into the 1950s with emerging global challenges, the U.S. sought to improve and modernize its nuclear arsenal. EBWs became the industry standard for detonators—even those outside weapon production, such as for mining and construction operations—and are now used around the world for their safety and reliability. The innovation that produced this new detonator standard still drives detonator design and assembly at Los Alamos today.

The team that comprised the South Mesa Detonator Group evolved into today’s Detonator Production division and has continually maintained an important part of the Lab’s national security mission.