Electron plasma wave propagation in external-electrode fluorescent lamps

Abstract

The optical propagation observed along the positive column of external electrode fluorescent lamps is shown to be an electron plasma wave propagating with the electron thermal speed of (kTe∕m)1∕2. When the luminance of the lamp is 10000–20000cd∕m2, the electron plasma temperature and the plasma density in the positive column are determined to be kTe∼1.26–2.12eV and no∼(1.28–1.69)×1017m−3, respectively.

Plasma Wave Propagation with Light Emission in a Long Positive Column Discharge

“…For the presentation of wave decay along the tube, we have the characteristic decay length, which should be above the scale of lamp length, about 1 m or 10 m according to the lamp current. In the previous reports [8][9], the fatal results of their analysis are that the waves are dependent of the electron drift velocity u d whose direction is changed with the voltage polarity. Therefore, they do not explain the direction of propagation observed in the experiments where the waves always propagate from high voltage side to the ground without decay or with a small decay.…”

“…As the display area becomes larger in LCD TVs, the tube diameter is 3~4 mm and the lamp length is up to 1~2 m. However, the mechanism for radiation of light along such a long positive column is not well understood. The characteristics of light emission in the EEFLs have been reported, specifically the propagation of a light-emitting along a tube driven by high voltage AC [8][9]. In the long positive column lamp, the light emits first from the side of high voltage propagates to the ground side with the propagation time of ~ s and the propagation velocity of 10 5~1 0 6 m/s.…”

“…In Ref. [9], the propagation velocity has been explained as the electron plasma wave propagation having an electron thermal speed u p~ue . However, the electron plasma wave has not been described completely whether the wave can propagate a long distance of about 100~1,000 mm and a long time of a few s since the damping time of an electron plasma wave is very short, about 10 -9 s. In those respects, the propagation of optical emission could be neither the electron drift nor the electron plasma wave of electron thermal speed.…”

“…In Ref. [8], the propagation speed u p was explained as the electron drift velocity, u p~ud . However, typical electron drift velocities driven by an electric field are u d ≤10 +4 m/s in a typical glow discharge plasma.…”

“…The fine-tube cold cathode fluorescent lamp (CCFL) [1][2] and external electrode fluorescent lamp (EEFL) [3][4][5][6][7][8][9], have been widely used as a backlight source in liquid crystal display (LCD) modules. In a notebook PC, the glass tube diameter of the lamp is a small as 1 mm.…”