Introduction  The 3.7 GHz high-power TH2103A klystrons are widely used in the tokamak experimental device. To simplify the HV power supply system (removing the vacuum tetrode in the anode modulation), a power supply mode based on voltage division mode is introduced into the TH2103A klystron of the HL-2A device. To operate the klystron safely in this power supply mode, a system for measuring and protecting the anode current of TH2103A klystron is developed.

  Method  According to the analysis of the characteristics of the anode current in this power supply mode, the anode current showed the condition of normal, forward overcurrent, or reverse overcurrent. In the case of forward overcurrent or reverse overcurrent, it meant that many electrons were bombarding or flowing out of the anode. They were very dangerous to the klystron, which usually may cause overcurrent of the klystron titanium pump, or even damage the klystron. Therefore it was important to accurately measure the anode current and cut off the high voltage to protect the klystron in case of overcurrent. The principle and power supply mode and the principle and implementation plan of the anode protection system were described in this paper.

  Result   In this paper, the effectiveness and reliability of the anode current measurement and protection system were confirmed.

  Conclusion  The power supply mode and the anode current measurement and protection system of this paper are of important reference significance for the operation and maintenance of TH2103A klystron.