The coaxial crossed field tube

In the coaxial crossed field tube**the magnetic field is not uniform but created by a large current flowing in a cylindrical rod; the delay line and the sole are also coaxial cylinders. Two possibilities exist: the delay line may be the inner or the outer conductor; in the ‘L’ band and at higher frequencies the size of an inner delay structure would involve too large a current; this solution would be interesting only for lower frequencies. The tube which will be described here is an experimental pulsed forward wave amplifier operating in the ‘L’ band; it is designed to give an output power of 0,6 MW; the beam impedance is very low, the cathode current being 53 A for a cathode vol tage of 28 kV; it results from this, that the delay ratio is unusually high for this peak power: it is 13 in the middle of the band. The copper stub in which the current flows constitutes also the sole the diameter of which is 14 mm. The line diameter is 32 mm and its length is 64 cm or 39 delayed wavelengths.