Luxemozione

After a long period I would start to publish some 'technical articles that I care about are enough and that apparently led to a moderate interest.
Today I would like to continue a discussion started a few months ago on the fluorescent lighting, introduced, always talking about the gas discharge lamps, the operating principle of the so-called "cold cathode" with particular attention to the spectral emission of noble gas filling.

To facilitate the reading divide this subject in a couple of episodes ... away with the part before then! good reading.

We saw in the last article as in fluorescent lamps "hot cathode" electrodes that are at the end of the glass tube, usually made from a tungsten filament, incandescent are taken (about 900 ° C) from the current flow, with consequent emission of electrons that triggers the download nell'Argon mixed with mercury (Penning mixture).

The process that defines the emission of electrons with these features is called " thermionic emission "which slowly consumes the filament-cathode limiting the average life of approximately 15 thousand ore.Diverso source is what happens inside the" cold cathodes "those that until recently were only intended for decorative insignia colored area of premises, but is now beginning to find a decent application in architecture, as a substitute just the most common fluorescent within the" luminous grooves "that increasingly are used to illuminate public spaces in hotels, theaters, restaurants, etc..

The cold cathodes are characterized by a cathode / anode consisting of a metal cylinder ° (and not a filament) that works up to about 200 ° C, from which the extraction of electrons ( secondary electrons ) takes place directly on the impact of positive ions metal cylinder.

This process is achieved through the use of operating voltage much higher than those normally used in hot cathode.

Thanks to its constituent characteristics of cold cathode, the average life guaranteed for this type of lamp is around 50,000 hours.

The cold cathodes are usually made of a glass tube variable area (10 to 15-20mm) at whose ends are welded electrodes and in which is inserted a single noble gas or mixture.
The noble gases normally used are 5 (of 6): Helium, Neon, Argon, Krypton, Xenon. When the gas inside the discharge tube is invested by the emission of electrons, they undergo a process of ionization and excitation with subsequent emission spectra specific for each gas mixture.
The emission spectrum is defined by its process of excitement when the electron "excited" jumps of orbital temporarily and then return to its initial state, during this process energy is released in the form of photons, for example.

As we shall see in the next episode the five gases (and mixtures thereof) once excited are characterized by an emission spectral characteristic, such as the Neon (the best known noble gas) is characterized by a red light intense enough.

Then a final consideration on cold cathodes, compared with traditional fluorescent emerge immediately say some negative aspects that would tip the balance in favor of the latter, such as high operating voltages, the costs are higher than average a traditional fluorescent lamp. However, most average life (greater than 50,000 hours), the smallest size installed, the customization of the system (glass tubes can be shaped as desired) and dimming without specific auxiliary sources make these extremely interesting.

the next episode

Hello everyone

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