The vacuum system is a necessary system to ensure the normal operation of the accelerator. It provides sufficient vacuum for the normal work of the accelerator, so that the electron beam can be accelerated and transmitted normally.The principle of the vacuum system is to use the vacuum exhaust system (vacuum pump) to exhaust the accelerating tube and so on, so as to achieve the vacuum degree needed for the accelerator to run normally.
A schematic diagram of the vacuum system of the accelerator(10Mev) is shown below,The position of the titanium pump in the diagram is a titanium sputtering ion pump, which is the main exhaust pump of the vacuum system. After the accelerator is completed, the ion pump has been working at all times and can not stop at any time.In addition to the main exhaust pump, a molecular pump unit is needed as the front pump because the ion pump cannot be started directly from the atmosphere.The molecular pump is designed to reduce the vacuum of a vacuum system from one atmosphere to about 1.3×10-1Pa（1×10-3torr）. Then the ion pump can be started. When starting the ion pump, it is necessary to observe the voltage and current of the ion pump until the vacuum gradually improves.
Diagram of the vacuum system of the accelerator(10MeV).
The technical performance of the vacuum system:
The vacuum system consists of a molecular pump unit, four ion pumps (including the power supply of the ion pump) and connecting pipes.
The molecular pump unit is a 550L/s air cooling unit with a pumping speed of 550L/s.
The ion pumps are 15L/s, 100L/s (2) and 50L/s respectively. The part of the electron gun is 15L/s ion pump (according to the needs of the electron gun), 100L/s ion pump at the inlet and outlet of the acceleration tube, 50L/s ion pump in the scanning box, and 25L/s ion pump in the waveguide tube.The auxiliary power supply of the ion pump is Shanghai sanjing company, and the high voltage output is 4 and 6kV. The ion pump uses 6kV high voltage.
