Spectral radiance of strong lines in positive column mercury discharges with argon carrier gas

Abstract

The spectral radiance of the 185 and 254 nm lines in two positive column mercury discharge lamps was measured over a wide range of operating conditions. The lamps had internal diameters of 5 and 23 mm. Argon was used as a carrier gas. The lamps were operated with cold spot temperatures of 20, 40 and 60 °C. At each of these temperatures, results were obtained for five currents ranging from 20 to 100 mA for the 5 mm lamp and from 200 to 1000 mA for the 23 mm lamp. For each current studied, results were determined for argon pressures ranging from 66.6 to 666 Pa (0.5 to 5.0 Torr) in the 5 mm lamp and 26.6 to 666 Pa (0.2 to 5.0 Torr) in the 23 mm lamp. An argon miniarc was used as the radiometric standard. By calibrating the spectral response of the optical system with a well-characterized mercury pencil lamp, results were obtained for 12 additional Hg lines from 289 to 579 nm. For the 23 mm lamp the electric field in the positive column was measured. For this lamp the radiated power as a percentage of input power was also determined. The results provide an experimental basis for validating computer models of Hg fluorescent lamp discharges.

Power balance in the positive column of narrow bore (T2) fluorescent lamps

“…a T12 (ID = 36 mm) has maximum 254 nm at 42 • C. As the radius is increased, there is increased trapping of radiation at the same cold spot temperature, leading to a reduction in the optimum cold spot temperature. In figure 7, the variation of 254 nm radiance with current for different cold spot temperatures is compared with similar data published by NIST [11]. In all cases, the 254 nm radiance increases as current is increased, but the rate of increase is reduced at higher currents and cold spot temperatures.…”

“…A complete list of cross sections used to calculate these reactions, together with all the reaction rates C ss jkmn and diffusion coefficients D s j included in the calculations, are provided in [16]. In the model, a complete set of coupled differential equations (11) for each atomic level is solved, with the radiation term set to zero for metastable levels. The diffusion time scale for radiative levels is several orders of magnitude slower than the radiative processes, but diffusion is included in the equations for completeness.…”

“…U s jk = 0 corresponds to the steady state Holstein-Biberman equation [29,30] (see also [31]). Note the vector notation is used to emphasize that U s jk at radius r includes contributions from all planes other than that of the one-dimensional axially symmetric model adopted for equation (11).…”

“…Narrow bore FL are also used in backlighting of LCD displays, such as computer screens and TV panels. Experimental studies have been reported in the literature for T4 (OD =14 mm) [8,9], T3 (OD =10 mm) [10], T2 (OD =7 mm) [11,12] and T1 (OD = 4 mm) [13,14]. Probe measurements of electric field and electron density in T1 FL have also been compared with results from a numerical model [13].…”

“…Discharges have been investigated for commutated dc currents from 20 to 200 mA and cold spot temperatures from 20 to 80 • C (0.16-11.8 Pa Hg vapour pressure). In addition to comparisons with results of a numerical model, results have been compared with those of similar experimental investigations [11].…”