Kylmäkatodit

Kylmäkatodit, also known as cold cathodes, are electrodes in a gas discharge tube that operate at or near room temperature. Unlike hot cathodes, which require significant heating to emit electrons, cold cathodes rely on other mechanisms to initiate and sustain a gas discharge.

One common type of cold cathode is the field emission cathode. In this setup, a very strong electric field is applied to a sharp point or edge, causing electrons to tunnel out of the material and into the surrounding gas. Another type is the secondary emission cathode, where the cathode is bombarded by ions from the gas plasma. This bombardment knocks electrons off the cathode surface, which can then ionize more gas molecules, creating a self-sustaining discharge.

Cold cathodes are often used in applications where a long lifespan, low power consumption, or resistance to high temperatures is desired. Examples include neon signs, cold cathode fluorescent lamps (CCFLs), and some types of vacuum tubes. Their ability to start a discharge at relatively low voltages makes them suitable for specialized lighting and display technologies. The term "kylmäkatodi" specifically refers to this type of electron emission without significant pre-heating.