Editing Princeton Plasma Physics Laboratory (section)

===Tokamak===
By the mid-1960s it was clear something was fundamentally wrong with the stellarators, as they leaked fuel at rates far beyond what theory predicted, rates that carried away energy from the plasma that was far beyond what the fusion reactions could ever produce. Spitzer became extremely skeptical that fusion energy was possible and expressed this opinion in very public fashion in 1965 at an international meeting in the UK. At the same meeting, the Soviet delegation announced results about 10 times better than any previous device, which Spitzer dismissed as a measurement error.

At the next meeting in 1968, the Soviets presented considerable data from their devices that showed even greater performance, about 100 times the [[Bohm diffusion]] limit. An enormous argument broke out between the AEC and the various labs about whether this was real. When a UK team verified the results in 1969, the AEC suggested PPPL to convert their Model&nbsp;C to a tokamak to test it, as the only lab willing to build one from scratch, [[Oak Ridge National Laboratory|Oak Ridge]], would need some time to build theirs. Seeing the possibility of being bypassed in the fusion field, PPPL eventually agreed to convert the Model&nbsp;C to what became the Symmetric Tokamak (ST), quickly verifying the approach.

Two small machines followed the ST, exploring ways to heat the plasma, and then the [[Princeton Large Torus]] (PLT) to test whether the theory that larger machines would be more stable was true. Starting in 1975, PLT verified these "scaling laws" and then went on to add [[neutral beam injection]] from Oak Ridge that resulted in a series of record-setting plasma temperatures, eventually topping out at 78&nbsp;million [[kelvin]]s<!-- the SI unit is in lower case and pluralized regularly -->, well beyond what was needed for a practical fusion power system. Its success was major news.

With this string of successes, PPPL had little trouble winning the bid to build an even larger machine, one specifically designed to reach [[fusion energy gain factor|"breakeven"]] while running on an actual fusion fuel, rather than a test gas. This produced the [[Tokamak Fusion Test Reactor]], or TFTR, which was completed in 1982. After a lengthy breaking-in period, TFTR began slowly increasing the temperature and density of the fuel, while introducing [[deuterium]] gas as the fuel. In April 1986, it demonstrated a combination of density and confinement, the so-called [[fusion triple product]], well beyond what was needed for a practical reactor. In July, it reached a temperature of 200&nbsp;million kelvins, far beyond what was needed. However, when the system was operated with both of these conditions at the same time, a high enough triple product and temperature, the system became unstable. Three years of effort failed to address these issues, and TFTR never reached its goal.<ref>{{cite journal |title=Results and Plans for the Tokamak Fusion Test Reactor |first=Dale |last=Meade |journal=Journal of Fusion Energy |volume = 7|issue=2–3 |date= September 1988 |page=107|doi = 10.1007/BF01054629|bibcode=1988JFuE....7..107M |s2cid=120135196 }}</ref> The system continued performing basic studies on these problems until being shut down in 1997.<ref name="TFTR-end">Staff (1996) "Fusion Lab Planning Big Reactor's Last Run", ''[[The Record (Bergen County)|The Record]]'', 22 December 1996, p.&nbsp;N-07.</ref> Beginning in 1993, TFTR was the first in the world to use 1:1 mixtures of [[deuterium]]–[[tritium]]. In 1994 it yielded an unprecedented 10.7&nbsp;megawatts of fusion power.<ref name="TFTR-end"/>