  The electron cyclotron heating system including four gyrotrons is under
developed in the Institute of Plasma Physics, Chinese Academy of Sciences. The
filament is an important part of the gyrotron, which is used to heat the
cathode. Each gyrotron has a filament power supply to adjust the filament
power. The filament power control and measurement system was developed to
control the beam current and the output power of the gyrotrons. The control
program was developed in Labview. The filament characteristics were tested
using the power control system. The test results show that the filament current
can be fitted with the e-exponential function of the filament voltage. It can
be seen that as the voltage increases, the filament resistance gradually
increases. The 'burst' function was developed to prevent the beam current from
dropping too fast. The filament control system can work stably for the
gyrotrons.
