The factors that determine the ultimate vacuum in the system of oil diffusion pumps and sealed off tube are studied.
In the case of two diffusion pump system, the ultimate vacuum of 1 ×10
-10mmHg (measured value) without liquid nitrogen trap is obtained by adjusting in put power of boiler heater.
In the one diffusion pump (Hickman pump), the ultimate vacuum of 1. 5×10
-10mmHg is obtained. But input power of boiler in the first case is larger than later case. In order to produce and maintain ultra high vacuum in the sealed off tube with B A ionization gauge, heating loop and parts must be made specially and thus pressure of 1. 5×10
-10mmHg can be maintained while electrodes are heated to 2800°K.
View full abstract