In 1973, only months after beginning operations, such an event burned holes through the vacuum vessel, requiring extensive repairs.
[3] After months of setup and calibration, by the summer of 1969 the measurements carried out under the supervision of Derek Robinson showed the results were even better than the Soviets had reported the previous year.
These results suggested that the tokamak was the first large-scale device that clearly beat a significant barrier to progress up to that date, Bohm diffusion.
By that time, TFR was the most powerful tokamak in the world, reaching ion temperatures of 1 keV and a Lawson criterion figure of 2.5 ⨉ 1012/cm³s.
This was one of the major problems with the basic tokamak design compared to earlier systems like Z-pinch that also strongly heated their plasmas.
To address this, TFR had planned almost from the start[12] to incorporate neutral beam injection, or NBI, which uses a small particle accelerator to fire individual atoms of fuel into the reaction chamber.
Soviet researchers had developed a new system using additional magnets and feedback control that prevented vertical movement of the plasma, which the shell had previously performed.
The system initially used a limiter made of molybdenum, whose high melting point allowed it to better absorb the heat load of the ions hitting it.
[13] By August 1981, the addition of five more NBI lines increased the ICRF heating power to 2.2 MW and produced plasmas at 2 keV at a high central electron density of 2 ⨉ 1014/cm³.
Around 1985, a new heating system, electron cyclotron resonance frequency, was installed in cooperation with the Institute for Plasma Physics Rijnhuizen (FOM).
[14] However, due to its internal arrangement, the TFR-600 had a larger 1 cubic meter useful plasma volume than other early tokamaks like the Soviet T-3.
The other major difference was the much larger power supply, which could provide up to 400,000 amps for up to a quarter of a second, or lower amperage for up to half a second.
Current was induced into the plasma using a transformer core placed between two of the toroidal magnets, its location can be seen by the large power cables running to it on the top of the assembly.
[7] The original version cost a total of 15 million francs, almost half of which was financed by Euratom's European Nuclear research and training program.