Princeton Large Torus


The Princeton Large Torus, was an early tokamak built at the Princeton Plasma Physics Laboratory. It was one of the first large scale tokamak machines, and among the most powerful in terms of current and magnetic fields. A key feature was the use of external heating systems to raise the temperature of the plasma fuel, a requirement of any practical fusion power device.
The tokamak became a topic of serious discussion in 1968, and the PPPL was convinced to convert their Model C stellarator to the tokamak configuration. It immediately validated the Soviet results. These early machines had no effective way to heat the plasma, so PPPL built the Adiabatic Toroidal Compressor to test one method of heating, adiabatic compression, while the PLT was designed to test another, neutral beam injection.
The PLT was extremely successful. It was the first tokamak with a plasma current over 1 MA. In 1978 it heated its plasma to 60 million degrees C, just above the critical threshold for a "burning plasma" that is seen as key to practical devices. These results led to the effort to build a machine capable of reaching breakeven, the Tokamak Fusion Test Reactor.

History

The PPPL website says:

Device details

says "Largely a copy of the Russian T-10, but with addition of NBI and LH systems. Demonstrated current drive from breakdown by LH, but that LH only effective in low density plasmas. Variable minor radius by adjusting limiter position. The first machine to achieve a plasma current of 1MA. Metal limiters replaced by carbon limiters... about 1978."