This generated significant skepticism among other researchers and it was some time before the PPPL was convinced to convert their Model C stellarator to the tokamak configuration.

The next step in developing the system would be to build a larger machine to test whether the confinement time of the plasma scaled as expected.

Around the time that PLT was being built, Oak Ridge National Laboratory had successfully introduced the neutral beam injection heating concept, or NBI.

PLT's success led the way for plans to build an even larger machine capable of reaching breakeven, a long-sought goal in fusion power.

When the physics of nuclear fusion was first put on a firm footing during the early 1950s, a string of proposed devices to harness that energy was quickly created.

There was some early doubt on this point; the only direct experience with plasmas, from the Manhattan Project, suggested the leakage rate was linear with the magnetic field.

[4] At a similar meeting in 1965 at the recently opened Culham Centre for Fusion Energy in the UK, the Soviet team introduced preliminary results on a device they called the tokamak.

Physically, it was very similar to the z-pinch concept, which had been extensively developed by the UK in the ZETA device and proved to be no more useful than other early systems, beset with instabilities.

In contrast, the Soviets were claiming that their seemingly minor variation on ZETA was producing dramatically better results, about 10 times the Bohm limit.

The directors of the fusion program within the Atomic Energy Commission (AEC) were interested in at least confirming or denying the Soviet results, but found the labs uninterested in such work.

In particular, the AEC felt it would be easy to convert Princeton's Model C stellarator to a tokamak, but the lab's director, Harold Furth, refused to even consider it, dismissing the Soviet claims out of hand.

[12] Only Oak Ridge National Laboratory showed any interest; they had no other large-scale devices in planning and were open to giving the tokamak a try.

The two returned from lunch to describe how to convert the Model C.[9] The conversion started in September 1969 and was completed eight months later as the rechristened the Symmetrical Tokamak.

[15] Finally, some system would be needed to extract impurities from the plasma, both from the initial non-pure fuel as well as removing "fusion ash", the results of successful reactions (typically helium).

Initially, this was the main goal of the Princeton Large Torus, but allowances were made that new forms of heating could be added to the machine without serious disruption.

This turned out to be an excellent way to heat the plasma as well, and Oak Ridge continued work on these lines using mirror reactors through the 1960s.

Their early calculations were not promising, but a visit by Bas Pease from the UK Culham fusion laboratory urged them to continue with this approach.

Worried about being redundant, the Oak Ridge team decided to adapt the ORMAK's transformer cage as the basis for a much larger tokamak and add NBI immediately.

[19] It was around this time that two Soviet theorists published a paper describing a worrying new problem in the tokamak concept, the trapped-particle instability.

John M. Deutch was placed in control of the DOE's Office of Energy Research, and immediately began plans to cut $100 million from its budget.

Published in June 1978, the "Final Report of the Ad Hoc Experts Group of Fusion" stated that "the momentum should be maintained", code for keeping the budget as is.

This was a milestone in the fusion program; PLT demonstrated that one could make a tokamak that could confine its plasma long enough to heat it to the temperatures needed in a practical reactor.

[29] Kinter was on holiday with his family at the time, and when they returned to their hotel in Stowe the next day the desk clerk told them there was a series of urgent messages waiting from Gottlieb.

[30] As was the case for both ZETA and the original tokamaks, the news was too good to keep bottled up, and the story began appearing at the other fusion labs within days.

On 31 July, Energy News ran a short front-page story talking about "persistent reports of a major breakthrough", prompting the DOE to plan for a 15 August press release instead of waiting until Innsbruck.

This was a serious mistake; Levitt's magazine was convinced there was a conspiracy to kill fusion research, and the denial from the DOE served to prove his suspicions.

The night before, vice president Walter Mondale had written to Schlesinger demanding he prepare a memo on the events, adding to everyone's tension.

Deutch did not let anyone else from the DOE talk, and told the press that it was a routine result that had long been expected and that lots of other energy programs were also making great progress.

News of an entirely different type is also being reported these days... Scientists at Princeton University have achieved a major success in the area of thermonuclear fusion.

[37] Work with the NBI beams continued, and eventually reached 2.5 MW to produce 75 million degrees, an event that was concluded with its own t-shirts.