kylmäkatodipurkaus

Kylmäkatodipurkaus, often translated as cold cathode discharge, is a type of electrical discharge that occurs between two electrodes at relatively low gas pressures. Unlike hot cathode discharges, which require a heated filament to emit electrons, cold cathode discharges rely on other mechanisms to initiate and sustain the flow of current. These mechanisms typically involve the emission of electrons from the cathode due to high electric fields or ion bombardment.

The process begins when a sufficient voltage is applied across the electrodes in a low-pressure gas. This voltage accelerates any free electrons present in the gas, causing them to collide with gas atoms. These collisions can ionize the gas atoms, creating more free electrons and positive ions. The electric field then accelerates these newly created electrons and ions towards the respective electrodes. When positive ions strike the cathode with enough energy, they can dislodge electrons from its surface. This electron emission, known as secondary emission, is crucial for sustaining the discharge without a heated cathode.

Common examples of devices utilizing cold cathode discharge include neon signs, fluorescent lamps (though often with a starter that initiates a glow discharge), and some types of gas-filled surge protectors. The spectral output of the light emitted depends on the type of gas used within the discharge tube. For instance, neon gas produces a characteristic red-orange light, while other gases can produce different colors or invisible ultraviolet radiation, which then excites a phosphor coating to produce visible light as in fluorescent lamps. The operating pressure, electrode material, and gas composition all influence the characteristics of a cold cathode discharge, such as its voltage-current relationship and light output.