Greenhouse Item (May 25), like George, tested new thermonuclear strategies, but with less complexity and a higher degree of confidence that all would work as planned. Item consisted of a spherically imploded fission bomb (not unlike the ones tested at Alamogordo and dropped on Nagasaki) with a small ball of deuterium and tritium at its center—this time the DT mixture was a gas at ordinary temperature, not a liquid. This was the booster principle first suggested by Edward Teller in 1945.[62] When the implosion compressed the fissionable material to criticality and beyond, the resulting explosion heated the DT ball at the center (as well as compressing it). Again 14-MeV neutrons were created and detected to verify the thermonuclear burning. Although the DT added only a small bit directly to the energy released, it augmented the fission yield greatly by furnishing neutrons (from DD as well as DT reactions) that entered the fissionable material and stimulated more fissions before everything could blow apart. In short, the boosting principle increased the bomb’s efficiency—that is, the fraction of its load of fissionable material that actually underwent fission. According to some estimates,{20} the 45.5-kiloton yield of Item was about twice what it would have been without the thermonuclear assistance.
Greenhouse George and Item (along with two other unrelated—but large—tests, Dog and Easy, carried out in April) had been set in motion more than a year earlier, not only before the Teller-Ulam radiation-implosion idea that changed everything, but even before the discouraging results of Ulam-Everett and Fermi-Planck were in hand. The test results, although hardly irrelevant—they provided lots of useful data and validated new designs—were not critical to deciding in what directions to go next. The equilibrium Super was on the front burner.
In the same month that the George and Item results flowed into Los Alamos and were being analyzed, I was in Albuquerque buying a camera, a small motorcycle, and goggles, in preparation for my return to Princeton.
Chapter 11
Constructing Matterhorn
When John Wheeler interrupted his stay in Paris to join the H-bomb effort at Los Alamos in early 1950, he imagined that he might need to remain at the Los Alamos lab for up to two or two-and-a-half years. There was, at the time, no clear path to success on the bomb—just the likelihood of a lot of hard work to bludgeon nature into submission.
His attitude changed after he had been in Los Alamos for half a year or so—not about the need for hard work, only about where that work should be performed. There were several reasons. First, he and Edward Teller had been notably unsuccessful in attracting other top scientists to the work. To be sure, Fermi, von Neumann, and Bethe, who were the best of the best, agreed to continue as consultants, as did the very young and very brilliant Dick Garwin. One physics professor, Lothar Nordheim, from Duke University, signed on for two years. That was it. No other fish bit, although the lures were cast far and wide to researchers at top universities. (Teller and Wheeler personally, not the lab authorities, were apparently the recruiters-in-chief, although Teller may have induced Norris Bradbury, the lab director, to sign some of the letters.) Some of those contacted didn’t see the need for a “crash program.” Others thought that their work on pure physics and with a new crop of graduate students was more important than weapons work. Others felt that they had done their bit during the recent war and were not ready to go back on what would be effectively a war footing. Neither the Soviet threat, which so alarmed Teller and Wheeler, nor the scientific challenge were enough to pry loose top physicists from their postwar pursuits. These are the themes of responses as described by John Wheeler to John Toll and me.
Wheeler began to wonder if geography was the problem. Could it be that if some piece of the work were done at a leading research university (Princeton) top physicists would join the effort? (It was, and they didn’t. Wheeler’s unsuccessful recruitment effort is something I address later in this chapter and again in Chapter 15.)
When, in the late fall of 1950, Wheeler made his pitch to the Los Alamos management for an ancillary effort to be based in Princeton, he added another argument, that important calculations could conveniently be carried out at the still-under-construction MANIAC computer at Princeton’s Institute for Advanced Study. (Again, hope and reality diverged. The MANIAC, in 1951 and 1952, was unable to deliver reliable performance, and Wheeler’s Princeton group turned to other computing resources.) Whether Wheeler attached real importance to being in the MANIAC’s backyard is doubtful. But when you are making a sales pitch, you marshal whatever arguments are available.
As important as any other consideration but no doubt missing from the official records was the attitude of Wheeler’s wife Janette. After her April 1950 arrival in Los Alamos, she tried hard to make her Bathtub Row house into a home and to fit into the life of what she perceived as a company town. She made friends with Francoise Ulam and continued her friendship with Mici Teller but remained bothered by the apparent correlation of town social life and rank in the lab. In truth, she desperately missed Princeton. In the fall, adding to her other discontents, she reached the conclusion that the Los Alamos public schools were substandard. I recall hearing Janette and John Wheeler discussing the possibility of sending their two older children (then twelve and fourteen) to a boarding school in Switzerland if John remained another year in Los Alamos. (Their youngest child, Alison, then eight, told me in 2013 that she enjoyed her year in Los Alamos but learned nothing. When she did return to Princeton, in 1951, it was to enroll in Miss Fine’s School, with its high standards matching those of her school in France.)
Driven by the various motivations, Wheeler prevailed. His first approach on paper to a Princeton official came in a letter of January 8, 1951 addressed to Allen Shenstone, his department chair (whose tenure in that position was to expire at the end of the month).{1} In his last two days in office, Shenstone made clear his opposition to the idea in communications to university president Harold Dodds and to Harry Smyth, his former Princeton colleague now in Washington as an Atomic Energy Commissioner—but to no avail.{2}{3} Within a few weeks, Smyth had expressed guarded support and the new department chair, Don Hamilton, relayed Smyth’s support and his own (with caveats concerning where and how secret work might be conducted) to President Dodds.{4} By April 1951, Project Matterhorn existed on paper (although not yet with that name), and Hamilton was communicating with Wheeler on the salary structure for the new project.{5} By June, project staff were at work in Princeton.