Editing Stellarator (section)

=== Model C ===
{{main|Model C stellarator}} 
As early as 1954, as research continued on the B-series machines, the design of the Model C device was becoming more defined. It emerged as a large racetrack-layout machine with multiple heating sources and a divertor, essentially an even larger B-66. Construction began in 1958 and was completed in 1961. It could be adjusted to allow a plasma minor axis between {{val|5|and|7.5|u=cm}} and was {{val|1,200|u=cm}} in length. The toroidal field coils normally operated at 35,000&nbsp;gauss.{{sfn|Stix|1998|p=7}}

By the time Model C began operations, information collected from previous machines was making it clear that it would not be able to produce large-scale fusion. Ion transport across the magnetic field lines was much higher than classical theory suggested. Greatly increased magnetic fields of the later machines did little to address this, and confinement times simply were not improving. Attention began to turn to a much greater emphasis on the theoretical understanding of the plasma. In 1961, [[Melvin B. Gottlieb]] took over the Matterhorn Project from Spitzer, and on 1 February the project was renamed as the [[Princeton Plasma Physics Laboratory]] (PPPL).{{sfn|Timeline}}

Continual modification and experimentation on the Model C slowly improved its operation, and the confinement times eventually increased to match that of Bohm predictions. New versions of the heating systems were used that slowly increased the temperatures. Notable among these was the 1964 addition of a small [[particle accelerator]] to accelerate fuel ions to high enough energy to cross the magnetic fields, depositing energy within the reactor when they collided with other ions already inside.{{sfn|Timeline}} This method of heating, now known as [[neutral beam injection]], has since become almost universal on [[magnetic confinement fusion]] machines.<ref>{{cite web |date=9 July 2012 |title=Neutral beam powers into the record books |url=http://www.ccfe.ac.uk/news_detail.aspx?id=166 |url-status=dead |archive-url=https://web.archive.org/web/20170324043543/http://www.ccfe.ac.uk/news_detail.aspx?id=166 |archive-date=24 March 2017 }}</ref>

Model C spent most of its history involved in studies of ion transport.{{sfn|Timeline}} Through continual tuning of the magnetic system and the addition of the new heating methods, in 1969, Model C eventually reached electron temperatures of 400&nbsp;eV.{{sfn|Johnson|1982|p=4}}