Sealing design requirements for vacuum electrodes

    ① The vacuum seal of the electrode lead device mostly uses rubber sealing rings, so water cooling should be added to the high current and high temperature to prevent the temperature from being too high and damaging the vacuum rubber ring, which affects the vacuum degree of the vacuum chamber;

    ② The vacuum seal should be reliable. Conductive copper rods should be required to have higher precision and smaller surface roughness, and should be coated with vacuum grease during assembly;

    ③ The diameter of the transmission line should be appropriate, and the current density should not be too large to prevent the transmission line from overheating;

    ④ Since there is a certain voltage on the transmission line, it must be insulated from the connection, especially for high-voltage transmission lines, this cannot be ignored. The selection of insulating materials should be based on factors such as voltage and temperature. Consider the material resistivity, surface resistivity, breakdown voltage and other issues;

    Commonly used insulating materials include vacuum rubber, glass, ceramics, glass cloth plates, glass cloth rods, yellow wax cloth, polytetrafluoroethylene and so on.

    ⑤ The influence of temperature should be considered. For transmission lines that need to be baked, they should be able to withstand a high temperature of 500°C. It is necessary to distinguish between the temperature that the lead is subjected to during baking and when there is no current, and the two conditions of heating during operation. If the transmission line is heated, avoid using any materials that cannot withstand the temperature in the structure.

    ⑥ The influence of frequency should be considered. At low frequencies, frequency has little effect on vacuum sealing, but at high frequencies, transmission lines and insulating materials should be determined according to special requirements. For example, when the frequency reaches 108Hz/s or more, it is used for power transmission. The resistivity of some materials of the wire may exceed the allowable value. For example, when Kovar alloy is used for high frequency, the sealing of the high frequency loss insulator will be heated to an impermissible degree. Therefore, the resistivity of the transmission line must be reduced or other materials must be used.

    ⑦ For the domestic JB type high voltage lead wire, because it is welded by vacuum ceramics, Kovar alloy, and stainless steel flanges, it has undergone strict vacuum leak detection, and the air leakage rate, insulation withstand voltage, current, temperature parameters, and baking temperature can reach performance It is required to have reliable sealing performance and good high-voltage insulation performance.

    ⑧ The connecting flange of the electrode flange of the electrode introduction part and the vacuum chamber should be designed according to the national vacuum flange standard, and participate in the design of the national standard vacuum standard to achieve the versatility and interchangeability of the electrode flange. If air leakage occurs at the lead-in part of the electrode during use, vacuum grease cannot be applied to stop the leakage, and the seal should be replaced.

(huiputech)