Maintenance of high vacuum level in a compact and lightweight sealed hard-tube magnetically insulated line oscillator system

• The outgassing characteristics of MILO in static and 440kV states were measured.
• We use the NEG pumping model to estimate the high vacuum life in static state.
• The simulation model is universal for vacuum tubes which are maintained by NEG.
• Two single-activated NEGs maintain MILO vacuum for more than 250 days at 25°C.
• One single-activated NEG maintains for 8 pulses under a voltage of 440 kV, 80 ns.

Magnetically insulated line oscillator (MILO) is compact and lightweight high power microwave tube. To maintain the MILO below 10−2 Pa, we used built-in non evaporable-getter (NEG). In comparison with other pumping technology, the NEG pump operates without power is lightweight and compact. To estimate the vacuum life in static state, we carried out experimental analysis to investigate the outgassing characteristics of the main materials of the MILO in static state. Considering the expected pumping characteristics of NEG pumps in combination with the experimental data, the conclusion is that at room temperature two NEG pumps will maintain high vacuum level in the MILO more than 250 days. Moreover, the pulse desorption characteristics of MILO under high voltage pulse operation (peak voltage 440 kV, pulse width 80 ns) were also measured. At room temperature, the evaluation shows that one NEG pump can maintain the MILO tube in high vacuum level for nearly 8 pulses.