Peri-cathode processes in fluorescent lamps

Розглянуто питання щодо механізмів утворення від’ємного катодного світіння, темних «дифузійних плям» та густих непрозорих замкнених смуг на стінках колб люмінесцентних ламп (ЛЛ) у навколокатодній області, причини виникнення периферійних пульсацій світлового потоку та страт як основного фактора, який обмежує глибину регулювання світлового потоку. Доведено, що утворення від’ємного катодного світіння в навколокатодній області ЛЛ зумовлено збудженням й іонізацією (в основному) атомів ртуті, а не аргону.The article deals with the problem of the negative cathode glow formation mechanisms, dark «diffuse spots»and thick opaque closed stripes on the flask walls of fluorescent lamps (FL) in the peri-cathode space, whence of peripheral pulsations of luminous flux and strata as a major factor that limits the depth of the luminous flux regulation. It has been determined a) that peri-electrode pulsations of the luminous flux in FL are preconditioned not only by the periodic change of the electrode polarity, when the movement of Faraday dark space from one end of the lamp to another takes place, but also by the fact that dimensions of the negative cathode glow over each half-period change cophasally while the Faraday dark space change antiphasally by the instantaneous value of the current; b) the relationship between the rate of the dark «diffuse spots» formation and the thick opaque closed stripes on the flask walls in the peri-cathode space, the quality of FL and modes of its functioning in the electric circuit. Great operating and starting currents activate this process noticeably. It has been proved that: a) the formation of the negative cathode glow in the peri-cathode space of FL is caused by excitation and ionization (mostly) of mercury atoms and not those of argon; b) at smooth current decrease through the FL, as is the case in the regulation of the luminous flux of lamps, the temperature of the cathode and anode reduces so much that the cathode becomes unable to emit a sufficient enough number of electrons to maintain a discharge process. It testifies that without an additional heating of the electrode the regulation depth of the FL luminous flux cannot be high. Besides, while operating in the industrial frequency network, an increase of the pulsation depth of the luminous flux will take place. There have been clarified the reasons of the strata’s appearance in the FL luminous flux regulation in high frequency electric circuits, which made it possible to set reasonable limits of its regulation by the current decrease through the lamp in no more than 5 times of the nominal current