Editing Tokamak (section)

=== 1980s: great hope, great disappointment ===
[[File:The JET magnetic fusion experiment in 1991.jpg|thumb|upright=1.5|[[Joint European Torus]] (JET), in operation from 1983 to 2023]]

By the late-1970s, tokamaks had reached all the conditions needed for a practical fusion reactor; in 1978 PLT had demonstrated ignition temperatures, the next year the Soviet T-7 successfully used [[superconducting]] magnets for the first time,{{sfn|Smirnov|2009|p=5}} Doublet proved to be a success and led to almost all future designs adopting this "shaped plasma" approach. It appeared all that was needed to build a power-producing reactor was to put all of these design concepts into a single machine, one that would be capable of running with the radioactive [[tritium]] in its fuel mix.{{sfn|Bromberg|1982|p=10}}

During the 1970s, four major second-generation proposals were funded worldwide. The Soviets continued their development lineage with the T-15,{{sfn|Smirnov|2009|p=5}} while a pan-European effort was developing the [[Joint European Torus]] (JET) and Japan began the [[JT-60]] effort (originally known as the "Breakeven Plasma Test Facility"). In the US, Hirsch began formulating plans for a similar design, skipping over proposals for another stepping-stone design directly to a tritium-burning one. This emerged as the [[Tokamak Fusion Test Reactor]] (TFTR), run directly from Washington and not linked to any specific lab.{{sfn|Bromberg|1982|p=10}} Originally favouring Oak Ridge as the host, Hirsch moved it to PPPL after others convinced him they would work the hardest on it because they had the most to lose.{{sfn|Bromberg|1982|p=215}}

The excitement was so widespread that several commercial ventures to produce commercial tokamaks began around this time. Best known among these, in 1978, [[Bob Guccione]], publisher of [[Penthouse Magazine]], met [[Robert Bussard]] and became the world's biggest and most committed private investor in fusion technology, ultimately putting $20 million of his own money into Bussard's Compact Tokamak. Funding by the [[Riggs Bank]] led to this effort being known as the [[Riggatron]].<ref>{{cite web |first=Robert |last=Arnoux |url=https://www.iter.org/newsline/151/468 |title=Penthouse founder had invested his fortune in fusion |website=ITER |date=25 October 2010}}</ref>

TFTR won the construction race and began operation in 1982, followed shortly by JET in 1983 and JT-60 in 1985. JET quickly took the lead in critical experiments, moving from test gases to deuterium and increasingly powerful "shots". But it soon became clear that none of the new systems were working as expected. A host of new instabilities appeared, along with a number of more practical problems that continued to interfere with their performance. On top of this, dangerous "excursions" of the plasma hitting with the walls of the reactor were evident in both TFTR and JET. Even when working perfectly, plasma confinement at fusion temperatures, the so-called "[[fusion triple product]]", continued to be far below what would be needed for a practical reactor design.

Through the mid-1980s the reasons for many of these problems became clear, and various solutions were offered. However, these would significantly increase the size and complexity of the machines. A follow-on design incorporating these changes would be both enormous and vastly more expensive than either JET or TFTR. A new period of pessimism descended on the fusion field.