page_title: Ivy Mike
section_title: Device design and preparations
hierarchical_section_title: Ivy Mike / Device design and preparations
caption_attribution_description: Outside the Mike shot cab
context_page_description: Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion.
  Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in Enewetak Atoll, in the now independent island nation of the Marshall Islands, as part of Operation Ivy. It was the first full test of the Teller–Ulam design, a staged fusion device.
  Due to its physical size and fusion fuel type, the "Mike" device was not suitable for use as a deliverable weapon. It was intended as a "technically conservative" proof of concept experiment to validate the concepts used for multi-megaton detonations.
  As a result of the collection of samples from the explosion by U.S. Air force pilots, scientists found traces of the isotopes plutonium-246 and plutonium-244, and confirmed the existence of the predicted but undiscovered elements einsteinium and fermium.
context_section_description: The 82 short tons (74 metric tons)  "Mike" device was essentially a building that resembled a factory rather than a weapon. It has been reported that Soviet engineers derisively referred to "Mike" as a "thermonuclear installation".
  The device was designed by Richard Garwin, a student of Enrico Fermi, on the suggestion of Edward Teller. It had been decided that nothing other than a full-scale test would validate the idea of the Teller-Ulam design. Garwin was instructed to use very conservative estimates when designing the test, and told that it need not be small and light enough to be deployed by air.
  Liquid deuterium was chosen as the fuel for the fusion reaction because its use simplified the experiment from a physicist's point of view, and made the results easier to analyze. From an engineering point of view, its use necessitated the development of previously-unknown technologies to handle the difficult material, which had to be stored at extremely low temperatures, near absolute zero. A large cryogenics plant was built to produce liquid hydrogen (used for cooling the device) and deuterium (fuel for the test).  A 3,000-kilowatt power plant was also constructed for the cryogenics facility.
  The device that was developed for testing the Teller-Ulam design became known as a "Sausage" design: 
  At its center was a cylindrical insulated steel Dewar (vacuum flask) or cryostat. This tank, almost 7 ft (2.1 m) across and more than 20 ft (6.1 m) high, had walls almost 30 cm (0.98 ft) thick. It weighed approximately 54 short tons (49 metric tons). It was capable of holding 1,000 L (260 U.S. gal) of liquid deuterium, cooled to near-absolute zero. The cryogenic deuterium provided the fuel for the "secondary" (fusion) stage of the explosion.
  At one end of the cylindrical Dewar flask was a TX-5 regular fission bomb (not boosted). The TX-5 bomb was used to create the conditions needed to initiate the fusion reaction. This "primary" fission stage was nested inside the radiation case at the upper section of the device, and was not in physical contact with the "secondary" fusion stage. The TX-5 did not require refrigeration.
  Running down the center of the Dewar flask within the secondary was a cylindrical rod of plutonium within a chamber of tritium gas. This "fission sparkplug" was imploded by x-rays from the primary detonation. That provided a source of outward-moving pressure inside the deuterium and increased conditions for the fusion reaction.
  Surrounding the assembly was a 5 short tons (4.5 metric tons) natural uranium "tamper". The exterior of the tamper was lined with sheets of lead and polyethylene, forming a radiation channel to conduct X-rays from the "primary" to the "secondary" stage. As laid out in the Teller-Ulam design, the function of the X-rays was to compress the "secondary" with tamper/pusher ablation, foam plasma pressure and radiation pressure. This process increases the density and temperature of the deuterium to the level needed to sustain a thermonuclear reaction, and compress the "sparkplug" to a supercritical mass - inducing the "sparkplug" to undergo nuclear fission and to thereby start a fusion reaction in the surrounding deuterium fuel.
  The entire "Mike" device (including cryogenic equipment) weighed 82 short tons (74 metric tons). It was housed in a large corrugated-aluminium building, called the shot cab, which was 88 ft (27 m) long,
  46 ft (14 m) wide, and 
  61 ft (19 m) high, with a 
  300 ft (91 m) signal tower.  Television and radio signals were used to communicate with a control room on the USS Estes where the firing party was located.
  It was set up on the Pacific island of Elugelab, part of the Enewetak atoll.  Elugelab was connected to the islands of Dridrilbwij (Teiteir), Bokaidrikdrik (Bogairikk), and Boken (Bogon) by a 9,000 ft (2.7 km)
  artificial causeway. Atop the causeway was an aluminium-sheathed plywood tube filled with helium ballonets, referred to as a Krause-Ogle box. 
  This allowed gamma and neutron radiation to pass uninhibited to instruments in an unmanned detection station, Station 202, on B
caption: The Ivy Mike shot cab and signal tower
exif: {}