ICRH Thomson tetrodes: from long pulses to CW

Thomson Tubes Electroniques tetrodes of the 2 MW class, the TH 525 and the TH 526, have now entered the industrial production line, and their amplifiers are fully operational. They have already made it possible to reach outstanding results on plasmas. At JET (Joint European Torus), 16 amplifiers (25-27 MHz) are fitted with TH 525 tetrodes, which each deliver 2 MW of RF power in 20 s pulses to a plasma load (voltage standing wave ratio up to 1.5:1). The JET teams have tested these tubes up to 2.7 MW peak. A record peak of 22.5 MW of ICRH (ion cyclotron resonance heating) power has been coupled to the plasma (26.3 MW at the amplifier output). Two TH 525 tetrodes have also delivered their RF power to the TEXTOR plasma for more than two years. Six generators with TH 526 tetrodes are also delivering 2 MW each during 30 s, between 35 and 80 MHz, at TORE SUPRA. They have also been tested with the same pulse length at 1.4 MW/120 MHz, and are operational at 1 MW at this frequency, with high figures of gain, bandwidth, and efficiency. The next generation of Thomson tetrodes will make it possible to reach the same levels of power at these frequencies in CW (continuous wave) operation, with an even higher efficiency