Performance Evaluation of Klystron Beam Focusing System with Anisotropic Ferrite Magnet

TL;DR

This paper evaluates a klystron beam focusing system using anisotropic ferrite permanent magnets, demonstrating comparable power output and improved efficiency potential over electromagnet systems, with reduced complexity and cost.

Contribution

It introduces a novel permanent magnet focusing system with anisotropic ferrite magnets for high-power klystrons, showing feasibility and identifying key factors affecting efficiency.

Findings

Achieved 798 kW peak output with the prototype system.

Permanent magnet system consumes less power than electromagnet systems.

Efficiency can be improved by reducing transverse multipole magnetic fields.

Abstract

A klystron beam focusing system using permanent magnets, which increases reliability in comparison with electromagnet focusing system, is reported. A prototype model has been designed and fabricated for a 1.3 GHz, 800 kW klystron for evaluation of the feasibility of the focusing system with permanent magnets. In order to decrease the production cost and to mitigate complex tuning processes of the magnetic field, anisotropic ferrite magnet is adopted as the magnetic material. As the result of a power test, 798 kW peak output power was successfully achieved with the prototype focusing system. Considering a power consumption of the electromagnet focusing system, the required wall-plug power to produce nominal 800 kW output power with the permanent magnet system is less than that with electromagnet. However, the power conversion efficiency of the klystron with the permanent magnet system was found to be limited by transverse multipole magnetic fields. By decreasing transverse multipole magnetic field components, especially the dipole and the quadrupole, the power conversion efficiency would approach to that with electromagnets.