Abstract :
Since the advent of Samarium-Cobalt magnets, traveling-wave tubes have entered a new phase in their development, which will secure first place for them in the power-frequency race for many years to come. The high fields which can be achieved (at reasonable cost) with rare-earth magnets permit the TWT designer to focus much higher currents through smaller helices than was possible in the past, Such dense beams can, however, impose extreme thermal loads on the fragile helix structure, when they are defocused by rf saturation and/or collector depression.
