W. Namkung

Dispersion characteristics of cusptron vacuum waveguide modes

With successful demonstration of the ‘proof-of-principle’ experiment of the cusptron, the configuration of the cusptron waveguide gains importance. Although the dispersion relation for the cusptron rf circuit has been derived and experimentally verified before, the detailed properties of its dispersion characteristics are not well understood. In this paper, we will examine various aspects of the dispersion properties in conjunction with the design process of the cusptron tubes. In particular, two unique properties of the cusptron rf circuit, the mixture and the specific grouping of the azimuthal mode numbers are closely examined and demonstrated with simple physics. Special emphases are on the identification and designation of the modes, the profiles of various field components, the spectral distribution with respect to azimuthal mode numbers, and their relation to the cusptron microwave tube design

Preliminary study of cusptron amplifier

The cusptron microwave tube concept is under development at NSWC as a compact high power device using the harmonic frequency generating scheme by an axis-rotating beam and a multivane circuit. Sixth and fourth harmonic frequencies have been independently generated with electronic efficiencies of approximately 10%. With this successful oscillator mode of operation, the cusptron is now being converted to an amplifier. The input and output couplers are one-turn loops located in different vanes. A TWT operating 4.0-8.0 GHz will be used as an RF driver. In this paper, we will present theoretical and experimental studies on the cusptron amplifier with a 30-50 keV, axis-rotating electron beam and a six-vane circuit.

System for velocity ratio measurements of an axis‐rotating electron beam

A novel system to measure the ratio of transverse velocity to axial velocity (α) of a low voltage, axis‐rotating electron beam is described herein. With the system, more information about the beam can be obtained than from the usual slit/phosphor screen system. Since most of the beam is undisturbed before the phosphor screen, the beam radius and azimuthal symmetry can be quantified in combination with the beam α along various axial positions. The diagnostic is applied to a Cusptron microwave tube to measure these electron beam parameters which are important for high tube efficiency. Two magnetic field profiles are used to study various causes of low beam quality, while a third profile is used in attempt to maintain a high quality beam. By using the described system, it is shown that the third profile significantly increases beam quality. The system can easily be extended to higher energy beams with an appropriate scintillator.