Large-output radio frequency power source

Demands for large-output radio frequency power sources (RF-PS's) have increasingly been expanding for various industrial uses as well as for accelerators and nuclear fusion. Studies have been focused on automatic synchronization; automatic load matching; use of an external computer for management of operation, control and data transmission; and linkage to other external equipment. For industrial radio frequency power sources, in particular, great importance is attached to reduction in size, energy consumption, costs and maintenance. As an example, an MW-class RF-PS for ICRF (ion cyclotron range of frequency) which was developed by the authors to be used with a nuclear fusion experiment system is described. Its major characteristics are: 1) frequency 20 - 47 MHz, 2) radio frequency output up to 1.5 MW, 3) pulse width up to 100 msec, and 4) load 50 Ω. Requirements to be considered in designing a final-stage amplifier are listed. Improvements are made to achieve matching between the load and the impedance of the final-stage tube over a wide frequency range. Improvements are also made in the anode blocking capacitors. Preventive measures are taken against parastic oscillation and other abnormal oscillations. (Nogami, K.)