Piece of the Sun : The Quest for Fusion Energy (9781468310412) Read online

  Meanwhile, the AEC had also allowed some declassification of the laser-fusion work being done in the weapons labs. Nuckolls argued strongly for the declassification of his scheme for using a bare drop of liquid D-T directly driven by lasers. Because no hohlraum is used, he argued, it wouldn’t reveal any secrets about weapon design, nor would the manufacturing details of precision fusion targets be out there because all that was required was an eye-dropper. The AEC acquiesced and this paved the way for the May 1972 International Quantum Electronics Conference in Montreal at which Nuckolls, Wood, Teller and others from Livermore presented much previously classified material. Basov led a delegation of Soviet researchers and other groups also discussed their work. The conference opened up laser fusion to a much wider scientific audience and played a similar role to that of the 1958 Geneva conference for magnetic fusion researchers. Nuckolls followed that in September with a now-famous paper in the journal Nature which gave more details of the directly-driven bare drop design and other declassified information. For many scientists around the world, this was their first detailed introduction to laser fusion.

  Livermore recruited new people for its rapidly expanding laser programme, including John Emmett from the Naval Research Laboratory who was an expert in Nd:glass lasers and would lead the programme. First, in 1973, they built the 100-J Cyclops just to gain experience in highly amplified lasers. They had to overcome many problems, including flashlamps that exploded and dust on the surfaces of glass discs of the amplifiers – the high-powered beam would heat up the dust, which would in turn damage the surface of the disc. Next, in 1974, came the 20-J Janus which, although a lower energy than Cyclops, had a much shorter pulse length (0.1 nanoseconds) to match the timing of target implosions. The first beamline was soon joined by a second to take the energy to 40 J. Funding for the project began to increase rapidly around this time, in part because of the Yom Kippur War and the Middle East oil embargo that followed. Money was poured into energy projects following that first oil crisis and, although laser fusion was never given the label of an energy project, more money was channelled into it via defence spending.

  John Emmett (left) and John Nuckolls with a laser amplifier.

  (Courtesy of Lawrence Livermore National Laboratory)

  Despite the money and resources that the government labs had at their disposal, they were not the first to observe fusion neutrons by imploding a target with a laser. That prize went to KMS Fusion. Brueckner had spent a frantic three years setting up his laboratory from scratch. He had hired eighty scientists and technical staff, contracted General Electric to make the laser to his specifications, modified the buildings Siegel provided in Ann Arbor and installed the laser. His team devised a clever way of making fusion targets. They made tiny micro-balloons with walls of extremely thin glass. To fill them with deuterium-tritium fuel they surrounded the micro-balloons with the gas mixture at high pressure of more than fifty atmospheres and heated them to 500 °C. At high temperature the glass becomes permeable and the D-T gases can diffuse inside. They then cooled the balloons and the fuel became trapped. If desired, the capsules could be chilled to extremely low temperature to condense the gases and create a thin layer of D-T ice on the inside of the glass. Meanwhile, Siegel had been working tirelessly to raise money for the research. He was wildly enthusiastic about fusion. He talked about fusion reactors small enough to fit into a garage that could provide power for a small community. To show off KMS Fusion’s technical skills his lobbyist in Washington would hand out medicine vials each containing 10 million micro-balloons. He secured $8 million from the British company Burmah Oil and he raised another $20 million by selling off more parts of KMS Industries but it proved hard to persuade other investors to pitch in until Siegel’s hyperbole was transformed into real results.

  Those results came in 1974 when they began imploding their glass targets with the new GE-built laser. As they only had one laser, Brueckner’s team reflected its light off two specially designed elliptical mirrors to produce an even distribution of light all over the target sphere. The laser pulses – delivering around 100 joules in 0.3 nanoseconds – compressed the D-T fuel to ten times its normal density as a solid and, to the delight of the team, produced lots of neutrons, often as many as 7 million from a single shot. Siegel, understandably, trumpeted the breakthrough far and wide. The press and scientists had been starting to grow weary of his frequent announcements of progress and scepticism had crept in. The neutron results served to silence those critics.

  Although KMS Fusion’s results were an unmistakable sign of fusion reactions taking place it was still a long way from a useful amount of energy. Each target would have to produce ten million times as many neutrons just to break-even with the amount of energy in the laser pulse. But it was a major proof-of-principle for laser fusion which thus far in the United States had existed mostly in computer simulations. That year the AEC slightly loosened the bounds of classification again so that researchers could talk publicly about hollow targets as well as Nuckolls’ bare drop model. As a result, Brueckner went to the American Physical Society meeting in Albuquerque, New Mexico, in October; was allowed to describe his experiments; and was duly lauded by his peers. To the frustration of researchers from Livermore, this commercial upstart seemed to be leading in what some were calling the ‘neutron derby.’ To further rub salt into their wounds, in March 1975 the Energy Research and Development Administration (ERDA), the new agency that took over the research parts of the AEC when it was wound down earlier in the year, awarded KMS Fusion a contract worth $350,000 to carry out shots on behalf of the Livermore researchers to validate their computer simulations.

  Despite these embarrassments, the Livermore team was starting to make some progress. Its Janus laser, which had two beams so that light could be directed at the target from two directions simultaneously, was beginning to produce results. Similarly, Rochester’s LLE had finished and was now operating its new laser. Called Delta, it had four beams and could produce a pulse with 1 kilojoule of energy. Now at both labs and at KMS Fusion, their years of simulating and predicting were butting up against the hard reality of experiments – and they were getting some unpleasant surprises. The first of these was plasma instabilities: when the laser beams hit the material of a micro-balloon target, the material that is kicked off the surface forms a cloud of plasma and this interacts with the beams in unpredictable ways. The plasma can scatter the incoming beams, preventing some of the laser energy from doing its job of imploding the target. The laser beams also heat up the electrons in the plasma and the superheated electrons can penetrate into the micro-balloon, heating up the fuel before the implosion gets started – high temperature fuel is much harder to compress than cool fuel.

  Teller had predicted there would be such problems. In the late 1960s he was listening to a presentation at Livermore by one of the laser fusion researchers who was describing how the beams would produce a plasma around the target. As the explanation proceeded, the scowl on Teller’s face deepened and deepened. Teller had been closely involved in the early days of magnetic confinement fusion and knew how devilish plasma could be. ‘Wait a minute. Wait a minute! Are you telling me that laser fusion involves REAL plasma physics?’ Teller asked. ‘Yes, sir, it does,’ replied the speaker. ‘Well,’ Teller said, with an air of disappointment, ‘it will never work.’

  When they encountered that real plasma physics, the teams of researchers concluded that they just needed more powerful beams to overcome the energy-dissipating effects of the plasma. More powerful beams meant new larger lasers. The lasers that they were working with – Delta, Janus and so on – were already big machines. With their master lasers, multiple amplifiers, optics to shape and condition the beams, and target chambers, each filled a large room. The next generation would require purpose-built experimental halls and cost tens of millions of dollars. At Rochester, Lubin had a vision of following Delta with a huge 24-beam Nd:glass laser called Omega but funding it would be a problem. The LLE
to date had been funded by the university, industry sponsors and New York State, but the sort of money they needed for Omega would require federal funding.

  Unlike its predecessor the AEC, the ERDA was outward looking and wanted its research to take place not just in the national laboratories but in industry and universities. Rochester saw this as an opportunity to get its foot in the door and get a slice of government funding. And, for the first time, Congress’ Joint Committee on Atomic Energy was holding a session entirely devoted to inertial confinement fusion and how to divide up ERDA’s budget for it in fiscal year 1976. Rochester University pulled strings in Washington to get Lubin a slot in front of the committee so that he could make a pitch for funding for Omega. But there would be a lot of competition for funds. Livermore had already started to work on a powerful new Nd:glass laser, the 20-beam Shiva. Other national labs were also due to make requests, as was KMS Fusion.

  At 2 p.m. on Thursday, 13th March, 1975, Senator Joseph Montoya called the session to order. He began by reminding the committee that the President’s 1976 budget request called for $212 million for fusion research, $144 million for magnetic confinement fusion and $68 million for inertial confinement, and pointed out that the US government had since the beginning of the programme in the early 1950s spent a total of around $1 billion on fusion research. He continued:

  We know that Fermi achieved criticality in the first reactor only 3 years after the discovery of the fission process. We recognize the engineering genius that put Americans on the Moon and brought them home, but we also recognize that Mother Nature has been very reluctant to give up her peaceful thermonuclear secrets. This is why the Joint Committee and the Congress have been willing to support two different approaches to fusion.

  Continued support, it seems to me, must be predicated on careful, step-by-step research programmes. Experience has shown to date that there is no quick solution to controlled nuclear fusion.

  With those cautionary words, the session began by hearing from Major General Ernest Graves, head of ERDA’s division of military applications which funded inertial confinement fusion. Graves noted that six labs had so far achieved implosion of a fuel pellet and some of those detected neutrons. The six were Livermore, Los Alamos, Rochester’s LLE and KMS Fusion, plus labs in France and Russia. He then listed a series of milestones which, with healthy levels of funding, the programme should be able to achieve. These included ‘significant thermonuclear burn’ – in other words an implosion in which several percent of the D-T fuel fuses – by 1977-78; ‘scientific break-even’ – energy output equals energy of laser pulse – between 1979 and 1981; and ‘net energy gain’ between 1981 and 1983. If these milestones were successfully met, he predicted a ‘test system’ would be operating by the mid 1980s and a ‘demonstration commercial plant’ by the mid 1990s. But the key to getting there, he said, was laser energy. ‘The pace of the overall programme depends on the rate of laser development and construction. This, in turn, depends upon the ingenuity of man and the level of funding,’ Graves told the committee.

  There followed talks by the directors of Los Alamos, describing their work on carbon dioxide gas lasers, and Livermore, discussing Shiva. The director of Sandia Laboratories spoke of their work on using beams of electrons instead of lasers to spark fusion. His laboratory was looking to build a new accelerator to test the feasibility of e-beam fusion. Then it was the turn of Moshe Lubin. He highlighted LLE’s achievements so far: implosion experiments achieving densities of thirty times that of a solid, neutrons detected, and the world’s only laser that can produce pulses with energies greater than a kilojoule and shorter than a nanosecond. All achieved without relying on federal funding.

  To move forward towards break-even, LLE wanted to build a new laser capable of 10 kilojoule pulses. Lubin estimated that this would cost $40 million over six years: $24 million from industrial sponsors for the operation of the new facility; $6 million from the State of New York for the laboratory building; and, he proposed, $10 million from ERDA for the laser itself. In contrast to the presentations from the national laboratories and their still partly classified research, Lubin painted a picture of an open user facility which researchers from all over the country could come to and use. He likened Rochester’s position in laser fusion to that of Princeton University in magnetic confinement fusion and said that in this early, fundamental phase of laser fusion research it was appropriate that ‘the probing environment and backing of significant research capabilities of a leading university should be selected as the logical place for a major open research facility.’ Lubin was taking a big risk: this was a field of research dominated by the large and influential weapons labs and supported by ERDA’s division of military applications and he was saying that one of its major research facilities should be placed in the open, academic atmosphere of a university.

  The final speaker was Kip Siegel. Siegel was in a tight corner. He had so far spent $20 million on KMS Fusion, cannibalising some forty-two divisions of the parent company KMS Industries to pay for the Ann Arbor laboratory which was by then one of the world leaders in laser fusion. But Brueckner and the KMS Fusion team had discovered, like their competitors at Livermore and Rochester, that compressing a fusion target was much more complicated than they had expected and overcoming the instabilities and laser-plasma interactions would require bigger and much more expensive lasers. Brueckner could not see how Siegel could afford it and so in autumn 1974 he had left KMS Fusion and returned to UC San Diego. Siegel was now without his key scientist and without the money to keep up with the government-funded fusion labs. He really needed to pull something out of the hat and that’s exactly what he did, although that was not what most people remember about his testimony that afternoon.

  A natural self-publicist, he surprised all assembled by stating that he was not there to talk about a laser fusion research programme. ‘What I am talking about today is a possibility of having a pilot plant in existence in 1979 and 1980 producing hydrogen or methane, utilizing a laser fusion reaction. We visualize methane going into the pipeline in 1985, starting to make up for the shortfall in natural gas that will exist at that time,’ he said. Siegel told the committee that KMS Fusion had, like all its competitors, assumed that the thing to do with all the high energy neutrons coming out of a fusion reactor was to use them to generate electricity. He said they got past this ‘mental block’ when the head of the Texas Gas Transmission Corporation came to him and asked: ‘Can’t you do something in fusion to produce gas?’ Texas Gas was facing a drop-off in natural gas reserves and was looking to find an alternative source to take advantage of all the pipelines that it already had installed. KMS Fusion did some experiments and, according to Siegel, found a way to produce hydrogen using neutrons. That hydrogen could be used to make methane at less than half the cost of other synthetic gas methods such as coal gasification.

  Siegel gave no details of his technique but it is possible that if aiming to use fusion neutrons in a chemical process rather than to generate electricity, you may not need such a high level of gain to make the process viable. This may explain Siegel’s extremely aggressive timetable for building a demonstration plant in just four or five years. He asked ERDA for funding or a loan of $60 million over three years for the plant, to be added to $15 million from KMS Industries and $40 million from Texas Gas. As he neared the end of his testimony Siegel suddenly stopped in mid-sentence. The hushed audience waited for him to continue but he uttered the word ‘stroke’ and collapsed. The session was halted as an ambulance took Siegel to the George Washington University Hospital. He died at 5 a.m. the following morning and his dream of generating fusion energy in the private sector, and of making gas using neutrons, died with him. KMS Fusion continued to work in the field but was never again a big player in laser fusion. Rochester, in contrast, won the funding it was seeking and a year later, in April 1976, a cornerstone-laying ceremony was held to mark the start of construction of the Omega laser building.

  Ther
e was another event that spring which would, in time, have a profound effect on laser fusion research: another international treaty limiting tests of nuclear weapons. Nations were already restricted to only testing weapons underground, but the Threshold Test Ban Treaty, which came into effect in March, abolished any tests of greater than 150 kilotonnes. This made it virtually impossible to design any new weapons in the megatonnes range or even to check that existing ones were working.

  One of the rationales for carrying out nuclear explosions was to test the effects of the blasts on satellites, warheads and other military hardware. The Pentagon expected that politicians would eventually agree on a total ban on nuclear tests, so at that time it was pouring millions of dollars into large facilities – including particle accelerators, nuclear reactors and electromagnetic pulse generators – that could simulate the radiation from nuclear explosions. The problem with these facilities is that each could only produce one type of radiation, such as x-rays, gamma-rays or neutrons. What they needed was something that could produce all of them at once, just like a real explosion – something like a nuclear weapon in miniature.

  A decade and a half earlier, weapons designers at Livermore had mocked Nuckolls’ ideas for laser fusion. Now they were beginning to get interested. Laser fusion’s tiny blasts really are like mini H-bombs and produce all the radiation that a full-sized bomb would. To test the radiation toughness of military hardware under reasonably realistic conditions all they had to do was open a port inside a fusion facility’s reaction chamber and attach the piece of hardware to the wall. The blasts didn’t even need to achieve high gain; all that was required was lots of neutrons and high-energy radiation. In addition, the tiny blasts could be used to study the ‘weapons physics’ at work in a bomb explosion and to provide real data to validate the computer simulations that designers used. In its last months of existence towards the end of 1974, the Atomic Energy Commission had initiated its first study of the prospects of laser fusion. Its conclusions were delivered to ERDA in March 1975 and it recommended ‘aggressive development’ of laser fusion technology and that the national research programme should be broadened out from the national laboratories into industry and universities. But the study also concluded that there were many difficulties to be overcome before laser fusion could be a viable energy source. Much more likely, the panel said, was that in the short term at least laser fusion would prove very useful in nuclear weapons simulation. From that time onwards there would always be a question mark over laser fusion research: is it an energy programme or a weapons programme?