In the last NEWS (Vacuum Electrode Introduction) , we briefly introduced the vacuum electrode. In order to further understand the vacuum electrode, so let’s learn the design requirements of the vacuum electrode.
1. The vacuum seal of the electrode lead device because of the use of rubber sealing ring, so the high current, high temperature should be added water cooling to prevent the temperature is too high and destroy the vacuum rubber ring, affecting the vacuum chamber;
2. The vacuum seal should be reliable. The conductive purple copper rod 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 power line should be appropriate, should not make the current density is too large, to prevent the power line overheating;
4. Because there is a certain voltage on the power line, it must be insulated with the connection, especially for high-voltage power lines, but can not ignore this point. The selection of insulating materials should be based on the size of the voltage, the influence of temperature and other factors. Consider the material resistivity, surface resistivity, breakdown voltage and other problems;
Commonly used insulating materials are vacuum rubber, glass, ceramics, glass cloth plate, glass cloth rod, yellow wax cloth, polytetrafluoroethylene and so on.
5. The effect of temperature should be considered. For power lines that need to be baked, they should be able to withstand high temperatures of 500 ° C. It is necessary to distinguish between the temperature of the lead during baking and when there is no current, and the two conditions of heating during work. If a power line is heated, avoid using any material in the structure that cannot withstand the temperature.
6. Should consider the influence of frequency, frequency at low frequency has little effect on vacuum seal, but at high frequency, power lines with insulation materials should be determined according to special requirements, for example, when the frequency reaches 108Hz/s or more, the resistivity of some materials used as power lines may exceed the allowable value, such as high frequency can be used as alloy, The seal of the high frequency loss insulator will be heated to an impermissible degree. It is therefore necessary to reduce the resistivity of power lines or to use other materials.
7. For the Chinese domestic JB type high voltage lead because it is made of vacuum ceramic, kovar alloy, stainless steel flange welding, after strict vacuum leak detection, leakage rate, insulation pressure, current, temperature parameters, baking temperature to meet the performance requirements, with reliable sealing performance and good high voltage insulation performance.
8.The electrode flange of the electrode introduction part and the connection flange of the vacuum chamber should be designed according to the national vacuum flange standard, and participate in the national vacuum standard design to achieve the universality and interchangeability of the electrode flange. If there is gas leakage in the electrode lead-in part during use, the vacuum grease can not be applied to plug the leak, and the seal should be replaced.
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