Editing Magnetic mirror (section)

===DCLC===
Although 2XII was nowhere near the level needed by Dean's demands, it was nevertheless extremely successful in demonstrating that the yin-yang arrangement was workable and suppressed the major instabilities seen in earlier mirrors. But as experiments continued through 1973, the results were not improving as expected. Plans emerged to brute-force the performance through the addition of [[neutral-beam injection]] to quickly raise the temperature to reach Dean's conditions. The result was 2XIIB, the B for "beams".{{sfn|Heppenheimer|1984|p=79}}

While 2XIIB was being set up, in November 1974, Fowler received a letter from Ioffe containing a series of photographs of [[oscilloscope]] traces with no other explanation. Fowler realized they demonstrated that injecting warm plasma during the run improved confinement. This appeared to be due to a long-expected but so-far unseen instability known as "drift-cyclotron loss-cone", or DCLC.{{sfn|Heppenheimer|1984|p=80}} Ioffe's photographs demonstrated that DCLC was being seen in Soviet reactors and that warm plasma appeared to stabilize it.{{sfn|Heppenheimer|1984|p=81}}

2XIIB reactor started real experiments in 1975, and significant DCLC was immediately seen. Annoyingly, the effect grew stronger as they improved the operating conditions with better vacuum and cleaning of the interior. Fowler recognized the performance was identical to that of Ioffe's photographs, and 2XIIB was modified to inject warm plasma during the center of the run. When the results were seen, they were described as "sunlight was breaking through the clouds and there was the chance that everything would be all right."{{sfn|Heppenheimer|1984|p=82}}