CATHODE PREHEATING UNIT (CPU)
One of the basic elements of modern electric vacuum devices (EVD), such as pentodes, a traveling wave tube (TWT), klystrons, etc. is a cathode preheating unit (CPU). The CPU is traditionally the most complex unit in the electric vacuum devices, because it includes an emitter providing electron emission and a heater that provides heating of the emitter to 1200°C. In addition, the requirements imposed on modern EVD, in particular, miniaturization of devices, complicate the task of developing and manufacturing CPU even more.
Our company has experience in the development and production of oxide and impregnated CPU. Single-beam and multi-beam emitters impregnated CPU have a size of 0.9 to 200 mm, the filament heating power from a few watts to several kilowatts, and an emission current densityof 1.0-30 A/cm2.
The heating of the CPU to 800-1200°C is provided by heaters, assembled on insulators, pulverized and fused.
To improve the electron-emission stability, the emitter surface is coated with an osmium film whose thickness is less than 1 micron.
In the CPU production use is made of rolled steel, wire, refractory powder metals of the domestic production. The production technology involves high temperature hydrogen or vacuum furnaces, laser and contact spot welding, vacuum systems of ion etching, deposition and calcination of the CPU, vacuum autocrucible electric-arc melting.