Thermal Analysis of Sheet Beam Gun for the Sheet Beam Traveling Wave Tube

The sheet beam gun (SBG) is operated at high temperature, and thermal expansion could induce huge electron beam degeneration. The previous SBG design, which did not take account of thermal expansion, obtained bad transportation performance. Experimental measurement showed that the distance variation between a cathode and an anode was larger than 0.42 mm, which could hugely degenerate beam performance. A new inner support rod with grooves was employed in this paper, and the heat power was reduced from 27 to 15.5 W, while the distance variation was reduced to 0.29 mm. The new SBG with adjustment according to the thermal expansion was fabricated and tested. The transportation rate after anode tunnel was enhanced to 98%, and the total transportation rate of sheet beam traveling wave tube with a period permanent magnet focusing structure was about 90%.