Encyclopedia
The
"Trinity" test was the first
test of a nuclear weapon, conducted by the
United States on July 16, 1945 at , thirty miles southeast of Socorro on what is now
White Sands Missile Range, headquartered near
Alamogordo,
New Mexico. It was a test of an
implosion-design plutonium bomb, the same type of weapon later dropped on
Nagasaki,
Japan. The detonation was equivalent to the explosion of around 20 kilotons of
TNT, and is usually credited as the beginning of the Atomic Age.
History
The creation of nuclear weapons arose out of political and scientific developments of the late 1930s. The rise of
fascist governments in
Europe and new discoveries about the nature of atoms converged in the plans of the
United States and the
United Kingdom to develop powerful weapons using
nuclear fission as their primary source of energy. The
Manhattan Project, as the Allied effort was called, culminated in the test of a nuclear weapon at what is now called
Trinity site in July 1945, and the
atomic bombings of Hiroshima and Nagasaki a few weeks later.
Development
While U.S. and British efforts to investigate the feasibility of nuclear weapons began as early as 1939, the effort at development only began in earnest in 1942 when it was transferred under the authority of the
U.S. Army and became the
Manhattan Project. The project focused on the development of fissile material to power the
nuclear chain reactions which took place inside the weapons, and the design of the weapons themselves at the top-secret
Los Alamos Laboratory in
New Mexico.
Hans Bethe ,
The Road from Los Alamos. American Institute of Physics ISBN 0-671-74012-1
From January 1944 to July 1945, the large-scale production plants were set in operation, and the fissile material thus produced was used to determine the features of the weapons. Multipronged research was undertaken to follow several angles of attack against the problem of bomb design. Early decisions about weapon design had been based on minute quantities of
uranium-235 and
plutonium created in pilot plants and laboratory
cyclotrons. From these results it was thought that the creation of a bomb was as simple as shooting one piece of fissile material into another to form a
critical mass.
The production of uranium-235 proved to be quite difficult with existing technology, but the production of plutonium was comparatively easier, as it was a by-product of specially constructed
nuclear reactors, the first of which was developed by
Enrico Fermi only in 1942. Reactor-grade plutonium, however, was considerably less pure than cyclotron-produced plutonium, and the presence of another isotope of plutonium in the resulting product meant that the simple "gun type" model of bomb design would not work: the presence of extra
neutrons meant that the weapon would pre-detonate with a greatly reduced yield. This problem, when discovered in 1942, led to a redesign of the plutonium bomb towards the idea of "implosion", by which a spherical core of plutonium would be compressed using conventional explosives, which would increase its density and thus create a critical mass.
The problem was then to construct a weapon which would precisely compress the plutonium sphere on all sides exactly equally—any error would result in a "fizzle" which would simply eject the valuable plutonium and not result in a large explosion. Because of the difficulties in creating the
explosive lenses for perfect compression using the existing technology, it was decided by Manhattan Project military leader General
Leslie Groves and scientific director
J. Robert Oppenheimer that a test of the concept would have to be undertaken before a weapon could be confidently used in war conditions.
Test planning
Planning for the test itself was assigned to
Kenneth Bainbridge, a professor of physics at
Harvard University, working under explosives expert
George Kistiakowsky. A proper site had to be located that would guarantee secrecy of the project's goals even as it planned to detonate a nuclear weapon of unknown strength, proper scientific equipment had to be assembled for retrieving data from the test itself, and safety guidelines had to be developed to protect project personnel from the results of an unknown and highly dangerous experiment. Official test photographer
Berlyn Brixner set up dozens of cameras to capture the event on film.
Test site
The site was part of the Alamogordo Bombing Range, now the
White Sands Missile Range. The test site is at the northern end of the range, between the towns of
Carrizozo and
Socorro, New Mexico, in the
Jornada del Muerto in the southwestern
United States .
Name
The exact origin of the name is unknown, but it is often attributed to laboratory leader
J. Robert Oppenheimer as a reference to the poetry of
John Donne. Oppenheimer had been exposed to Donne primarily through his former girlfriend Jean Tatlock, who had committed suicide in July 1944. In 1962, General
Leslie Groves wrote to Oppenheimer on the origin of the name, asking if he had chosen it on the basis that it was a name common to rivers and peaks in the West and would not attract attention. "I did suggest it, but not on [that] ground... Why I chose the name is not clear, but I know what thoughts were in my mind. There is a poem of John Donne, written just before his death, which I know and love. From it a quotation: 'As West and East / In all flatt Maps—and I am one—are on, / So death doth touch the Resurrection.'" . Oppenheimer continued, "That still does not make a Trinity, but in another, better known devotional poem Donne opens, 'Batter my heart, three person'd God;—.' Beyond this, I have no clues whatever." . Richard Rhodes,
The Making of the Atomic Bomb . Quotes regarding the naming of the test from p. 571-572.
Test predictions
Betting pools were set up among the observers for the results of the test. Some predictions ranged from zero, a dud, to 18 kilotons of TNT , to destruction of the state of
New Mexico, to ignition of the atmosphere and incineration of the planet . As it turned out, Rabi won the bet.James Hershberg ,
James B. Conant: Harvard to Hiroshima and the Making of the Nuclear Age. 948 pp. ISBN 0-394-57966-6 p. 233
Test preparation
There was a pretest explosion of 108 tons of
TNT on May 7 to calibrate the instrumentation. For the actual test, the plutonium-core
nuclear weapon, nicknamed
the gadget, was hoisted on the top of a 20-meter steel tower for
detonation — the height would give a better indication of what the weapon would be like when dropped from an airplane, as detonation in the air would maximize the amount of energy applied directly to the target , and would kick up the least
nuclear fallout.
The "
gadget" was assembled at the nearby
McDonald Ranch House, the components arriving on July 12. It was assembled on the 13th and precariously winched up the tower the following day. In case of failure, a huge steel canister code-named "Jumbo" was prepared to recover the valuable plutonium at the order of General Groves. Weighing 240 tons, "Jumbo" was meant to contain the explosion from the 5 tons of conventional explosives used to compress the plutonium in case the chain reaction failed. At great expense, "Jumbo" was constructed in
Pittsburgh, Pennsylvania, and brought out to the test site by rail, but by the time it arrived the confidence of the scientists was high enough that they decided not to use it. It was instead hoisted up in a steel tower 800 yards from the "gadget", as a rough measure of how powerful it would be. In the end, "Jumbo" survived, though its tower did not.
The detonation was initially planned for 4:00 a.m. but was postponed due to rain and lightning from early that morning. Under conditions of rain it was feared that the danger from radiation and fallout would be greatly increased, and the lightning put the scientists on edge about the possibility of an accidental detonation.
The explosion
At 4:45 a.m. a crucial weather report came in favorably, and at 5:10 a.m. the twenty-minute countdown began. Most of the top-level scientists and military officers were observing from a base camp, ten miles southwest of the test tower. Many other observers were around twenty miles away, and some others were scattered at different distances, some in more informal situations . The final countdown was read by physicist
Samuel K. Allison.
At 05:29:45 local time , the device exploded with an energy equivalent to around 19 kilotons of TNT . It left a
crater of radioactive glass in the desert 3 meters deep and 330 meters wide. At the time of detonation, the surrounding mountains were illuminated brighter than daytime for one to two seconds, and the heat was reported as being as hot as an oven at the base camp. The observed colors of the illumination ranged from purple, to green, and eventually to white. The roar of the
shock wave took 40 seconds to reach the observers. The shock wave was felt over 160 km away, and the
mushroom cloud reached 12 km . As
Los Alamos director J. Robert Oppenheimer watched the demonstration, he later said that a line from the Hindu scripture the
Bhagavad Gita came to mind:
I am become Death, the destroyer of worlds.Test director
Kenneth Bainbridge replied to Oppenheimer, "Now we are all sons of bitches." According to Oppenheimer's brother, Frank, at the time of the test Robert simply said, "It worked."
News reports quoted a forest ranger 150 miles west of the site as saying he saw "a flash of fire followed by an explosion and black smoke." A New Mexican 150 miles north said, "The explosion lighted up the sky like the sun." Other reports remarked that windows were rattled up to 200 miles away and the sound of the explosion could be heard at just as great a distance.
In the crater the desert sand, which is largely made of silica, melted and became glass of a light green color and mildly radioactive; this was named
Trinitite. The crater was filled in soon after the test.
A recent paper reports the levels of long lived radioisotopes in the trinitite. The trinitite was formed from
feldspar and
quartz which were melted by the heat. Two samples of trinitite were used; the first was taken from between 40 and 65
meters of ground zero while the other sample was taken from farther away from the
ground zero point.
The
152Eu and 154Eu was mainly formed by the neutron activation of the europium in the soil, it is clear that the level of radioactivity for these isotopes is highest where the neutron dose to the soil was larger. Some of the 60Co is generated by activation of the cobalt in the soil, but some was also generated by the activation of the cobalt in the steel tower. This 60Co from the tower would have been scattered over the site reducing the difference in the soil levels.
The 133Ba and 241Am are due to the neutron activation of barium and plutonium inside the bomb. The barium was present in the form of the nitrate in the chemical explosives used while the plutonium was the fissile fuel used.
It is interesting to note that the 137Cs level is higher in the sample which was farther away from the ground zero point, this is thought to be because the precursors to the 137Cs and the cesium to a lesser degree are volatile. The natural radioisotopes in the glass are about the same in both locations.
The Alamagordo Air Base issued a 50-word press release noting "an explosion of a remotely located ammunitions dump, in which no one had been killed or injured." The actual cause was not publicly acknowledged until after the August 6 attack on Hiroshima.
The Manhattan Project's official journalist, William L. Laurence, had previously put multiple press releases on file with his office at the New York Times is a newspaper [i] published in New York City [i] by Arthur Ochs Sulzberger Jr. [i] ...
to be released in case of an emergency, ranging from a successful test to more macabre scenarios explaining why all of the scientists had perished in a single freak accident.
Around 260 personnel were present, none closer than 9 km. At the next test series, Operation Crossroads in 1946, over 40,000 people were present.
Test results
The results of the test were conveyed to President Harry S. Truman and were used by him as leverage in his negotiations with the Soviet Union at the Potsdam Conference. Truman was, however, somewhat shocked by Joseph Stalin's lack of response when he told him in private about the weapon; Stalin was already well aware of the American endeavor — through espionage.
Following the success of the Trinity test, two bombs were prepared for use against Japan. The first, dropped on Hiroshima, Japan, on August 6, was code-named "Little Boy", and used uranium-235 as its fission source. It was an untested model, but seemed very likely to work and was considerably more simplistic in design than the implosion model; in any event, it could not be tested as there was only enough uranium-235 for one bomb. The second bomb, dropped on Nagasaki, Japan, on August 9, was code-named "Fat Man", and was a plutonium bomb of the type tested at the Trinity test. The atomic bombings of Hiroshima and Nagasaki killed at least 120,000 people outright and many more over time, but were alleged by many internationally credible sources to have saved many more lives in the long run.
The information about the Trinity test was made public shortly after the bombing of Hiroshima. The Smyth Report, released on August 12, 1945, gave some information on the blast, and the hardbound edition released by Princeton University Press a few weeks later contained the famous "bulbous" pictures of the Trinity fireball.
Oppenheimer and Groves posed for reporters near the remains of the mangled test tower shortly after the war. In the years after the test, the pictures have become a potent symbol of the beginning of the so-called "atomic age", and the test has often been featured in popular culture.
The site today
In 1952 the site of the explosion was bull-dozed and the remaining trinitite was disposed of. On December 21, 1965, Trinity Site was declared a National Historic Landmark district, and was administratively listed on the National Register of Historic Places on October 15, 1966.
More than fifty years after the test, there is still a little residual radiation at the site, about ten times higher than normal.Brian Greene , Nova: The Elegant Universe: Einstein's Dream. Regarding residual radiation. Officials maintain that the amount of exposure received during a one-hour visit is far less than that received from eating food and being exposed to the sun. The Trinity monument, a rough-sided, lava rock obelisk around 12 ft high, marks the explosion's hypocenter, and "Jumbo" is still kept nearby, along with a model of the "Fat Man" bomb dropped on Nagasaki.
The site is still a reasonably popular destination for those interested in atomic tourism, though it is only open to the public twice a year, on the first Saturdays of April and October. On July 16, 2005, a special tour of the site was conducted to mark the 60th anniversary of the Trinity test and hundreds of visitors arrived to commemorate the occasion.
See also
References
External links
