First tests of the Varian EIMAC X2242 at 110 and 130 MHz in the JT-60 ICRH system

The Varian EIMAC X2242 utilizes pyrolytic graphite screen and control grids and a high-density mesh cathode in a new multimegawatt tetrode. It is capable of delivery 3 MW of output power. The first tests of the device performed in a modified, well-instrumented, JAERI (Japan Atomic Energy Research Institute) Tokamak-60 (JT-60) ICRH (ion cyclotron range of frequencies) amplifier, are described. The tests were run at 110 and 131 MHz at pulse widths to 10 s. Output power to 1.5 MW at 110 MHz and 1.6 MW at 131 MHz was observed. The amplifier was stable with significant reverse screen grid current. Internal examination of the tube after its return showed it to be undamaged, illustrating the high-temperature capabilities of pyrolytic graphite. Means of increasing tube power output at these frequencies are being developed