Plasma propagation along the long positive column plasma: I. light signal observations

Summary form only given. The light propagation along a long positive column has been observed in a fine-tube fluorescent lamp and a general lighting fluorescent lamp, such as a cold cathode lamp (CCFL), an external electrode lamp (EEFL), and a hot cathode lamp (HCFL). The observations are conducted in the operation of DC voltage as well as AC voltage. However, these observations of light propagation along a long positive column is the first report in 70-years history of long discharge lamps such as neon-sign lamps, fluorescent lamps for general lighting, and CCFLs and EEFLs for LCD-TVs.The experimental observations are summarized as: (i) Light always propagates from the high voltage side to the ground. The propagation direction is independent of the electron drift velocity ud whose directions are varied according to the electric field with polarity of the applied voltage, (ii) The speed of light propagation is u_p~(10⁵-10⁶) m/s according to the lamp current. The light propagation velocity is u_p~10⁵ m/s at a low current _~1 mA. As the current increases at the normal glow, the propagation velocity also increases over 10⁶ m/s. (iii) The optical signals represent the type of ripple wave as 0(t)=O₀+dOsinωt. When the operation frequency is ω₀ in AC-voltage, the frequency of optical ripple wave is ω=2ω₀, 2-times of AC-operation frequency. At a low current before breakdown, the signals decay along the z-direction of positive column as O(t, z)=O₀+dOexp(-z/zD)smωt. The decay scaling is about the lamp length L as z_D~L. At the normal glow of high current, the optical signals would not decay much with a large decay scaling as z_D>L and the ripple ratio is about dO/O_0~20-30 %.