Kylmäkatodia

Kylmäkatodia refers to a type of electrical discharge that occurs at relatively low temperatures and pressures. In this phenomenon, a vacuum or a gas-filled chamber contains two electrodes, a cathode and an anode. When a sufficient voltage is applied between these electrodes, electrons are emitted from the cathode. This emission is not due to the heating of the cathode to incandescence, as in hot cathode discharges, but rather through other mechanisms such as field emission or secondary emission caused by ion bombardment.

The emitted electrons then travel towards the anode, colliding with gas atoms or molecules present in the chamber. These collisions can ionize the gas, creating more ions and electrons, which sustains the discharge. The term "kylmäkatodi" specifically emphasizes the fact that the cathode itself does not need to be heated to a high temperature to initiate and maintain the electrical discharge.

Kylmäkatodi discharges have various applications. They are fundamental to the operation of devices like neon signs, fluorescent lamps, and some types of vacuum tubes. In these applications, the discharge is used to produce light, either directly through the excitation of gases or indirectly by causing phosphors to glow. They are also employed in some types of gas lasers and in vacuum measurement devices. The low operating temperature of the cathode in these discharges offers advantages in terms of energy efficiency and lifespan compared to hot cathode devices in certain scenarios.