SATELLITE TECHNICAL AREAS

Places > LOS ALAMOS: THE LABORATORY

As the research and development effort at the Los Alamos gradually shifted from theory and laboratory experimentation to engineering, fabrication, and field testing, the work increasingly spread from the Main Technical Area (TA-1) to the various satellite testing and technical areas set up in remote areas of the site. A total of 25 satellite areas eventually were built away from the main area and town site, primarily for safety reasons, and, by June 1945, 40 percent of the laboratory buildings were at these outlying sites. Among the most significant satellite technical areas were:

Omega Site (TA-2), located in Los Alamos Canyon below the Main Technical Area about a half mile down canyon, housed the Water Boiler Reactor. Completed in April 1944, the reactor ran on liquid enriched uranium fuel within a stainless-steel sphere one foot in diameter, and due to its very low power output was also known LOPO (low-power). The reactor was used to check theoretical critical mass calculations and the effects of tamper materials. The LOPO reactor was redesigned in mid-1944 and rebuilt for higher power operation as the HYPO reactor. At the same time, critical assembly experiments for the implosion device began at the site. These continued at the Omega Site until August 21, 1945, when Harry Daghlian accidentally received a lethal radiation dose from a brief supercritical arrangement of his critical assembly experiment. As a result of this accident, critical assembly work was transferred to Pajarito Site.

Two Mile Mesa Site (TA-6), located several miles to the south and west of the main area, was used to conduct research on detonators and engineering tests of high explosives assemblies. The site also was used to develop methods for recovering active plutonium in the event that the field-test of the implosion device failed. Still existing at the site is the large 200-foot-diameter concrete bowl used for recovery experiments.

Trinity device assembly building, V Site, Los Alamos

Anchor Ranch Site, located to the south and west of the Two Mile Mesa Site, consisted of the Anchor West Site (TA-8) used for gun testing, with a large flat area for gun emplacements immediately adjacent to a small canyon that gave natural protection to the control building during test shots, and the Anchor East Site (TA-9) used to cast the high explosives for the earliest implosion studies, with a small casting building in operation from October 1943 until early 1945 when it was superseded by the large-scale casting operations at the newly completed S Site high explosives facilities. Still existing at the gun site is the control building.

Bayo Canyon Site (TA-10), located to the east in the second canyon north of the main area, housed the RaLa firing program that studied implosions using radiation from a radiolanthanum (RaLa) source. Initially, when the program began in September 1944, doubts existed concerning the amount of contamination expected from an imploded source equal to hundreds of grams of radium, and precautions included using sealed M-4 army tanks to view the tests. The actual tests were less of a problem than expected, and more permanent facilities were constructed by November. Laboratory and support buildings included a chemistry building, assembly and inspection buildings, a personnel building, control buildings, and firing pads.

Sawmill Site or S Site (TA-16), located south of the Anchor Ranch Site, was the principal site that developed, tested, and manufactured high explosives castings and lenses for the implosion design. The largest of the satellite sites, with eventually over 80 buildings, magazines, and even its own dining hall, the S Site initially included an office building, a steam plant, a casting house, storage magazines, and high explosives preparation buildings. Due to construction delays and difficulty procuring equipment, the site operated only on a limited basis until May 1944 and did not begin steady operation until August. A major problem was that there were no existing methods for high explosives casting given that the military's standards for explosives performance were well below what was needed to develop a symmetrical implosion. The S Site facilities produced about 20,000 usable castings over an 18-month period—over 100,000 pounds of high explosives were used per month during S Site's peak operation. Several types of explosive materials were used in the casting process: Composition B, Torpex, Pentolite, Baronal, and Baratol.

Pajarito Laboratory (TA-18), located about ten miles south and east of the main area and containing usable buildings associated with a failed dude ranch—the Pajarito Club—abandoned in 1916, was used for several different projects. Beginning in mid-1943, the Radioactivity Group used ionization chambers and amplifiers to study samples of plutonium and to determine counting rates from spontaneous fission at this remote site because of the need to work away from the high-radiation background levels being produced at the Main Technical Area. This work led to the abandonment of the plutonium gun bomb design in July 1944. Later in 1944, Pajarito Canyon became a proving ground for the magnetic method of studying implosions. "Battleship Buildings" (earth-covered bunkers) were used to conduct the implosion tests. Full-scale tests of high explosives assemblies were also conducted.

Pajarito Laboratory became the main site for critical assembly work in April 1946. Critical assemblies were still operated by hand until Louis Slotin's death in May 1946. Like Daghlian at the Omega Site the prior year, Slotin received a lethal radiation exposure from a critical assembly experiment. The building where the accident occurred still exists at the site. V Site (TA-25), located near the S Site, was used to test mockups of both the implosion and gun devices. A functional mock-up of the plane and bomb-suspension was set up for handling, loading, shaking, and cold tests. The site also was used to assemble the high explosives components of the Trinity device. The building used for assembly still exists at the site.

Sources and notes for this page

The text for this page is original to the Department of Energy's Office of History and Heritage Resources. Portions were adapted or taken directly from Ellen D. McGehee, et al., Sentinels of the Atomic Dawn: A Multiple-Property Evaluation of the Remaining Manhattan Project Properties at Los Alamos (1942–1946) (Los Alamos National Laboratory, LA-UR-03-0726, March 28, 2003), 22-23, 25-30, 35-37, 42-43; Vincent C. Jones, Manhattan: The Army and the Atomic Bomb, United States Army in World War II (Washington: Center of Military History, United States Army, 1988), 507; David Hawkins, Manhattan District History: Project Y, The Los Alamos Project, Volume I, Inception Until August 1945 (Los Alamos Scientific Laboratory, LAMS-2352 [Vol. I], 1961), 81, 106, 116-20, 129-30, 141-42, 146, 207, 229-35, 244-47, 251; Edith C. Truslow, with Kasha V. Thayer, ed., Manhattan District History: Nonscientific Aspects of Los Alamos Project Y, 1942 through 1946 (Los Alamos Scientific Laboratory, LAMS-5200, March 1973), 24; Lillian Hoddeson, et al., Critical Assembly: A Technical History of Los Alamos during the Oppenheimer Years, 1943-1945 (Cambridge: Cambridge University Press, 1993), 100, 116-19, 148-54, 166-67, 199-203, 234-38, 268-74, 327.