Los Alamos:Part 4

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Continued from Los Alamos:Part 3, see also Los Alamos:Part 1 and Los Alamos:Part 2

The new IBM punched-card machines were devoted to calculations to simulate implosion, and Metropolis and Feynman organized a race between them and the hand-computing group. "We set up a room with girls in it. Each one had a Marchant. But one was the multiplier, and another was the adder, and this one cubed, and all she did was cube this number and send it to the next one," said Feynman. For one day, the hand computers kept up: "The only difference was that the IBM machines didn't get tired and could work three shifts. But the girls got tired after a while."

Feynman worked out a technique to run several calculations in parallel on the punched-card machines that reduced the time required. "The problems consisted of a bunch of cards that had to go through a cycle. First add, then multiply, and so it went through the cycle of machines in this room - slowly - as it went around and around. So we figured a way to put a different colored set of cards through a cycle too, but out of phase. We'd do two or three problems at a time," explained Feynman. Three months were required for the first calculation, and Feynman's technique reduced it to two or three weeks.

The first implosion calculation showed that the fissile material would be strongly compressed and that a high yield would result from assembling a relatively small amount of fissile material if a spherically symmetrical implosion was produced. Although much work on explosives lenses, detonators and other components of the device was required to accomplish this, the Trinity test July 16, 1945, showed that the calculation was correct. About a dozen other calculations of implosion were done to refine it before the end of the war.

In the meantime, von Neumann brought news of computer developments elsewhere, such as Bell Laboratory's relay computer and Howard Aiken's Mark I electromechanical calculator at Harvard where Aiken was director of the Harvard Computation Laboratory. The Mark I was even used to run an unclassified version of one of the Los Alamos problems. Although it took several times as long as the Los Alamos machines, it computed to far greater precision.

Von Neumann saw that problems like those encountered at Los Alamos could be solved by electronic computers similar to the electronic numerical integrator and calculator (ENIAC) being developed at the University of Pennsylvania. In 1944 and 1945, he formulated ways to translate mathematical procedures into a language of instructions for such a machine. And he recommended to Teller, who had conceived of a thermonuclear or "super" bomb, that one of the computational problems associated with its design be used to test the ENIAC, because it would be much more demanding than the ballistic trajectories the Army had designed it to calculate. Metropolis and Frankel traveled to the University of Pennsylvania early in 1945 to discuss the problem with the developers of ENIAC, John Mauchly and J. Presper Eckert.

The calculations were run in December 1945 and January 1946. A half-million punched cards of data were transferred from Los Alamos to Philadelphia to run it, and mathematician Stan Ulam, who von Neumann had recruited to come to Los Alamos from Princeton, recalled "the spirit of exploration and of belief in the possibility of getting trustworthy answers in the future. This partly because of the existence of computing machines that could perform much more detailed analysis and modeling of physical problems."

In the postwar era, von Neumann continued to arrange for access to the ENIAC for Los Alamos scientists and also built an improved version of the electronic computer at the Institute for Advanced Study at Princeton, where Oppenheimer became director. Inspired by his example, Los Alamos had Metropolis build the mathematical analyzer, numerical integrator and computer, or MANIAC, which was completed in 1952 and was responsible for the calculations of Mike, the first hydrogen bomb. It was followed by MANIAC II, the IBM-built STRETCH supercomputer and a series of commercial super computers that have made the Laboratory the world's largest scientific computing center.

Von Neumann also helped Ulam and Metropolis develop new means of computing on such machines, including the Monte Carlo method, which has found widespread application. His influence on the development of electronic computers was far-reaching, and he continued to foster their development at Los Alamos up to the time of his death in 1957 while serving on the Atomic Energy Commission.

The wartime work of the Laboratory created a need for computing that stimulated von Neumann, Metropolis, Ulam and others to reduce previously insoluble physical problems to a form in which they could be calculated automatically. The use of these techniques not only made possible the design of nuclear and thermonuclear weapons, but also the solution of many other scientific problems, ranging from aerodynamics to molecular biology. What began with a brief visit to the Laboratory by von Neumann in September 1943, has become a revolution in science and technology.

In October 1943, the 9812th Special Engineer Detachment (SED) of the Manhattan Engineer District (MED) began to supply technical personnel to the Laboratory. Scientists who had not been recruited in the early days of the Laboratory, but who had been drafted into the Army, were now routed to New Mexico to make a different contribution to the war than any they could have anticipated.

So, even though Robert Bacher, who headed the Experimental Physics Division, and other Los Alamos scientists had refused to don a uniform, the military had scientists in uniform at Los Alamos. In fact, 42 percent of the Laboratory wore uniforms. "Although the Army had failed to get the senior scientists in uniform as it wanted to, it did succeed in getting some very young men who were students in engineering and physics - some of them with Ph.D.s."

Bernice Brode, the wife of Robert Brode who was in charge of the group that designed fusing and firing of the bomb, recalled in her "Tales of Los Alamos," "The SED boys were quite different from the regular post soldiers. They looked, in spite of the uniforms, like budding professors instead of combat troops. Shortly after they came up to the Hill, some high brass from Washington came for a formal military review in the baseball field in front of the Big House (at Fuller Lodge).

"All of us came with our children to see the show. The MPs, the post soldiers, the Women's Army Corps (WAC) and even the doctors made a fine upright showing as they marched across the field, but the newly arrived SED boys were terrible. They couldn't keep in step. Their lines were crooked. They didn't stand properly. They waved at friends and grinned. The situation was not helped by the fact that they received the loudest applause from the bleachers. The visiting brass let it be known that they were displeased, and one general even called them a disgrace to the army."

Despite their performance as GIs, these young men "worked long hours in the tech area," according to Brode, and "although they often worked late into the night to meet a deadline, they were expected to arise at dawn for inspection and drill by tough sergeants from the regulars.

"Once, when a sergeant became irritated by his yawning, half-hearted crew and shouted, If you guys think I like this job, you got another think coming,' one of the SED boys offered to lead the drill in his place. He shouted orders in imitation of the sergeant's voice: Thumbs up, thumbs down. Thumbs wiggle-waggle.' Even the sergeant broke down and dismissed them. My husband and others who used the SED boys finally got their discipline relaxed, the drill stopped, and the inspection let go so they could sleep in the morning."

By the end of 1943, nearly 475 SEDs had arrived. By 1945, the unit included 1,823 men. Most were mechanical, electrical and chemical engineers. About 29 percent of them had college degrees. Because of their special skills, exemption from drill was not the only privilege accorded them. They were all permitted to be non-commissioned officers, and two-thirds of them ranked sergeant or higher.

Since many had no basic training, the members of other military units, such as the military police, who were also assigned to Los Alamos, resented their "apparent infringement on the military prerogative." According to Lt. Edith C. Truslow, a WAC then at Los Alamos, "Even before the nature of the project was published, many enlisted men tried to obtain transfers to the SED."

The SED was the result of the shortage of scientific and technical personnel at the time the Laboratory was founded.

In May 1943, the MED had established the detachment with an initial allotment of 675 men, divided into a headquarters detachment and four separate companies. Soldiers were recruited through the Army specialized training program, at universities and colleges throughout the country, and the Roster of Scientific and Specialized Personnel. The National Defense Research Committee, founded to mobilize academic and industrial science in 1940, had compiled the roster.

The establishment of the 9812th SED at Los Alamos allowed the MED to route civilian scientists and technicians whose deferments they could not or would not arrange to the Laboratory. The MED was often reluctant to intervene with local draft boards to secure deferments because it could not reveal the nature of its work. In late 1943, however, when fathers and those with occupational deferments began to be drafted, Laboratory Director J. Robert Oppenheimer predicted disaster for the project. The MED's Selective Service Section took drastic steps to secure their deferments, and by the end of the war, more than 60,000 deferment actions, involving scientists at Los Alamos; Oak Ridge, Tenn.; Chicago; and Berkeley, Calif., among other MED installations, were processed.

Nevertheless, when in February 1944 the War Department forbade the deferment of men under 22 in the employment of the Army or its contractors, a number of the younger civilian scientists found themselves drafted and reassigned to the Laboratory as members of the SED. They thus joined those who had already been inducted and wound up far from the front.

For those who were drafted and wound up in the SED, conditions were, if superior to their uniformed companions, inferior to those of civilian scientists who had won deferments at Los Alamos. Unlike them, SED technicians and scientists could not bring their families to Los Alamos or to surrounding communities.

Their commander, Maj. Peer de Silva, who was also the Post Military Intelligence Officer, refused to allow their wives to be hired at Los Alamos so that they could be quartered on-site. This, the official Army history tells us, "severely strained the morale of many junior scientists and technicians."

As they arrived at Los Alamos, the members of the SED found themselves assigned to test sites being completed at Anchor Ranch and S-Site. As they became familiar with the work, they won support from their civilian supervisors in matters of military discipline and promotion. George Kistiakowsky, who headed the division in charge of explosives development at S-Site, took their complaints to Oppenheimer and MED Commander, Gen. Leslie Groves.

Riding back to Albuquerque with the general after one of Groves' trips to Los Alamos, Kistiakowsky insisted that the SED receive better treatment. "Of course Groves immediately told me that as a civilian I had no business to tell him anything about Army matters," Kistiakowsky recalled, "and I said that the SEDs were part of my technical staff, they had to report to me, they had to work for me and therefore I had the authority. Well, I got absolutely nowhere. I then used my ultimate weapon: I said I would resign."

Before he could resign, Maj. T.O. Palmer was appointed to replace de Silva as commander of the SED in August 1944. He developed a system under which the groups and divisions made promotion recommendations. This maintained morale, even though conflicting military and laboratory duties continued to be a problem.

In addition to the ordnance test sites, SEDs were assigned to the group of computers working under Richard Feynman using IBM punched-card calculators. Feynman objected to the Army's refusal to tell the SEDs what they were working on. "They came to work, and what they had to do was work on IBM machines-punching holes, numbers that they didn't understand. Nobody told them what it was."

Feynman convinced Oppenheimer to get special permission "so I could give a nice lecture about what we were doing, and they were all excited: We're fighting a war; we see what it is!' They knew what the numbers meant." This led to a "complete transformation" according to Feynman. "They began to invent ways of doing it better. They improved the scheme. They worked at night, they invented several of the programs that we used, and so my boys came through, and all that had to be done was to tell them what it was."

Val Fitch, who later won a Nobel Prize in Physics recalls, "A number of young men, like myself, very early in their lives and careers, were exposed to superb physicists who were remarkable in many respects, and it had a profound influence upon us." After another summer at Los Alamos in 1948, Fitch received his Ph. D. from Columbia University in 1954 and went on to win the 1980 Nobel Prize in Physics for his work in particle physics.

Many other members of the SED went on to scientific careers. Los Alamos provided all of them an opportunity to associate with some of the leading physicists, chemists and metallurgists of their time. Some, like Bill Hudgins, returned to Los Alamos to work on the MANIAC and STRETCH computers. Gerold Tenney, a long-time group leader in WX Division and others also became part of the postwar staff. Among those who had to don a uniform in World War II, the SEDs were surely among the most fortunate. Before they could muster out, however, the SEDs had to complete the biggest test of all - Trinity.

The Los Alamos Laboratory was organized in 1943 to design a nuclear weapon that the Army hoped would win World War II. In the course of the next two years, the Laboratory designed a weapon using uranium-235 assembled by firing one part of a critical mass into another, but this technique was found to be inadequate for plutonium, because isotopic impurities of plutonium-240 would cause it to predetonate.

In the second year of its existence, therefore, the Laboratory was reorganized to solve the much more difficult problems of implosion - the uniform compression of plutonium to a super-critical mass � that had been proposed by Seth Neddermeyer of the California Institute of Technology, John von Neumann of the Institute for Advanced Study at Princeton and others.

Trinity test site

Because of the uncertainties attending almost every phase of the implosion weapon, it was decided almost at the beginning of the effort that the implosion bomb would have to be tested. After various test sites were considered, a location in the Jornado del Muerto desert in central New Mexico was selected. Harvard physicist Kenneth Bainbridge planned and University of Minnesota physicist John Williams supervised the construction of the facilities to support a test there.

Los Alamos Director J. Robert Oppenheimer named the site "Trinity" after a poem by John Donne that he had been reading. To capture the plutonium that might be lost if the bomb fizzled, Manhattan Engineer District Commander Leslie Groves ordered a container, called "Jumbo," to be built at a cost of more than $12 million. Jumbo was the largest item that had ever been shipped by rail, and several trestles on the railroads from the factory that built it in Ohio to the Trinity site had to be rebuilt.

By the time Jumbo arrived, the production of plutonium at the Hanford Engineer Works had increased so that Groves was less chary of it, and Oppenheimer and his colleagues believed that there was less chance of a fizzle. Consequently, the container was relegated to the sidelines and hung not far from Ground Zero to serve as an indicator of the power of the bomb. It emerged unscathed although the tower was destroyed.

The construction of the Trinity site was rapidly accomplished in the winter and spring of 1945, and by June, Bainbridge was ready to calibrate the instruments that would be used to measure the blast, heat and radiation of the "gadget" using a 100-ton stack of high explosives tagged with fission products from the Hanford pile. The 100-ton test was the largest man-made explosion up to that time and made it possible for the Los Alamos scientists to refine their instruments before the much larger blast anticipated from the gadget.

The design of the gadget had been fixed in February 1945 when Groves ordered a design freeze so that the device could be ready by July. A conservative solid-core design by Robert Christy, a member of the Theoretical Physics (T) Division, the gadget required the development of detonators, fuses and high-explosive lenses that were not yet perfected. Given a clear goal, however, Los Alamos scientists and technicians succeeded in producing all of the components of the device successfully by July 13.

On that day, assembly of the gadget began at Trinity. A crew led by Norris Bradbury, a professor of physics at Stanford University who had come to Los Alamos by way of the Naval Reserve and Dahlgren Proving Grounds, assembled the high-explosive lenses that had been brought from V-site at Los Alamos the day before escorted by Harvard professor George Kistiakowsky, who had led the high-explosives effort at the Laboratory since November 1943. Bradbury, Kistiakowsky and five �G (gadget) engineers' began their work at 1 p.m. After the tamper and the active material were inserted into the spherical case, the final high-explosives were inserted, "as slowly as the G-engineers wished," said Kistiakowsky.

Saturday, July 14, 1945, the assembled gadget was hoisted to the top of the 100-foot tower on which it would be detonated. The firing unit was wired by late afternoon. Bradbury's schedule for Sunday, July 15, called for the staff to "look for rabbit's feet and four-leaved clovers." The detonation was scheduled for 4 a.m., Monday, July 16.

Meantime, Los Alamos scientists had conducted a test of the implosion assembly at Los Alamos that seemed to indicate that it would not work.

Kistiakowsky was roundly criticized by Groves and Oppenheimer. His peacetime boss, James Bryant Conant of Harvard University, who was the scientific head of the atomic bomb effort, subjected him to a two-hour interrogation as to the causes of the failure of that effort. Kistiakowsky, however, was sure that the assembly would work, and Theoretical Division Leader Hans Bethe got him off the hook when he reported that calculations showed that the detectors used for the Los Alamos test could not have distinguished between success and failure.

As the test approached, the weather worsened, as the meteorologist assigned to predict it had warned. A thunderstorm broke over the site late on July 15, and the test was postponed from 4 a.m. to 5:30 a.m. to avoid the possibility of a rain-out of fission products from the bomb cloud. In nearby settlements, members of the health physics team were ready to evacuate the population should the test greatly exceed expected yields. Although most scientists believed that the yields would be low, Edward Teller, group leader of the Super and General Theory Group (F-1) in F (Fermi) Division, bet that it might exceed 40 kilotons, and Enrico Fermi, head of F Division, was heard taking side-bets that the bomb would incinerate New Mexico. Groves called the governor of New Mexico to alert him that an evacuation of the state might be required.

Oppenheimer was in a state of high tension during the early morning hours, but, as predicted, the weather cleared and the countdown for the test was begun at 5:10 a.m. "As we approached the final minute," Groves recalled, "the quiet grew more intense. I was on the ground (at Base Camp) between [ Vannevar] Bush [chairman of the Office of Scientific Research and Development] and Conant. As I lay there in the final seconds, I thought only what I would do if the countdown got to zero and nothing happened." At the control point, Joe McKibben, who had been with Project Y since the beginning, threw the switch that started the precise automatic timer at minus 45 seconds. Only Donald Hornig, a physical chemist from Harvard University, on the arming party, could stop the explosion.

At 5:29:45 a.m., the gadget exploded with a force of 21,000 tons of TNT, evaporating the tower on which it stood. Groves' deputy, Gen. Thomas Farrell, wrote that the "whole country was lighted by a searing light with the intensity many times that of the midday sun. It was golden, purple, violet, gray and blue. It lighted every peak, crevasse and ridge of the nearby mountain range with a clarity and beauty that cannot be described but must be seen to be imagined. Seconds after the explosion came first the air blast pressing hard against the people, to be followed almost immediately by the strong, sustained awesome roar that warned of doomsday and made us feel we puny things were blasphemous to dare tamper with the forces heretofore reserved for the Almighty." Oppenheimer was reminded of the quotation from his favorite Sanskrit text, the Bhagavad-Gita, "I am become Death, the Destroyer of Worlds." To his brother, Frank, who had helped construct the site, he said only, "It worked."

Los Alamos had succeeded in producing a nuclear weapon only two years, three months and 16 days after it was formally opened. The implosion bomb was, however, a vast departure from the nuclear weapon first envisaged. That device, the gun-type uranium weapon, did not need to be tested. Farrell commented to Groves immediately after the Trinity test, "The war is over." "Yes," Groves replied, "just as soon as we drop one or two of these things on Japan."

Los Alamos:Part 1, Manhattan Project

References

• Adapted from the Wikipedia article, "Los Alamos National Laboratory" http://www.wikipedia.org/wiki/Los_Alamos_National_Laboratory August 11, 2003