Katodisks

Katodisks are disk-shaped cathodes used as electron sources in vacuum electronic devices. The term is a compact form of disk cathode and appears in some technical discussions, though in standard English the devices are more commonly described as disk cathodes.

Construction and coatings: Katodisks are typically made from refractory metals such as tungsten or rhenium. They may be coated with emissive materials to lower the work function, including oxide coatings on tungsten or more advanced materials such as lanthanum hexaboride (LaB6). The disk geometry provides a relatively large emission surface while retaining a compact form factor, and many designs incorporate a heater element to thermally stimulate emission.

Operation: In use, electrons are emitted from the disk surface when thermally excited or facilitated by the emissive coating. The emitted electrons are drawn toward a positively biased anode, creating an electron beam within the vacuum enclosure. A nearby grid or electrode can regulate the emission current and help shape or focus the beam, enabling integration into various tubes and electron-optical systems.

Applications: Disk cathodes serve as electron sources in a range of vacuum electronic devices, including X-ray tubes, older cathode-ray tubes, electron microscopes, and certain high-power microwave sources. Their simplicity and robustness make them a common choice where a steady, high-current electron source is required, particularly in devices that operate under high vacuum.

Performance and maintenance: Emission performance depends on temperature, coating integrity, and vacuum quality. Over time, coatings can degrade or become contaminated, reducing brightness and stability. Devices using katodisks generally require careful vacuum maintenance and periodic replacement of the emissive surface.

Notes: The term katodisk is uncommon in contemporary English literature; disk cathode is the more widely used designation.