X-ray absorption imaging of Hg vapour in a ceramic metal-halide lamp using synchrotron radiation

Abstract

The diagnostic technique of x-ray absorption imaging of Hg vapour in high-intensity discharge lamps has been extended. X-ray absorption imaging has been used previously to determine the time-averaged absolute Hg density (Curry J J, Sakai M and Lawler J E 1998 J. Appl. Phys. 84 3066). Now, using an intensified charge-coupled device detector and synchrotron radiation, time-resolved measurements have been made. Although no significant time-dependence was seen as a function of the electrical phase for an electronically ballasted lamp, real-time observations were made of the decaying Hg density during the cool-down period. The cold-spot temperature in a 150 W ceramic lamp containing Hg and rare-earth iodides decreased with a time constant of 48.4 s following arc extinction. The primary limitation to the sensitivity of these measurements has been identified, and methods for overcoming this limitation in future work are proposed. Other aspects of the technique are also discussed.

Temperature profiles and thermal losses in 150 W high-intensity discharge lamps

“…Terms up to n = 16 were utilized, resulting in a spatial resolution of approximately 300 µm. This is much finer spatial resolution than was achieved in earlier work [6,12] and allows us to more fully resolve the steep gradients in density and temperature near the wall. (The measured column densities are also smaller than in previous work as a result of the smaller lamp size.)…”

“…In previous work [12], we used the intensifier of an intensified CCD detector to synchronously gate the acquisition of data. This allowed us to obtain time-resolved measurements in different phases of the alternating current cycle and during the cool-down period [6,15]. In the present case, we are interested in time-averaged measurements and the use of an un-intensified CCD eliminates noise generated by the intensifier.…”

“…Because the density and variety of molecules usually increases in moving from the core of the discharge to the wall, the determination of temperatures and densities in the mantle is of particular interest. Optical techniques are able to determine temperatures in the core [4], while x-ray techniques can be used to extend the temperature determination all the way to the discharge wall [5,6].…”

Quantitative x-ray absorption imaging with a broadband source: application to high-intensity discharge lamps

“…Previous work on x-ray absorption imaging of HIDs utilized both monochromatic x-rays from a synchrotron source [1,2] and broadband x-rays from commercial tube sources [3][4][5][6]. The commercial tube sources provide advantages in cost, convenience and, surprisingly, in sensitivity [7].…”

Comparison Between X-rays Absorption and Emission Spectroscopy Measurements on a Ceramic Envelop Lamp

“…X-rays diagnostic techniques have already been applied in the field of high intensity discharge lamps [4,5] to measure density distribution of mercury in 'transparent' discharge lamps. Here, we implement this technique in the case of translucent burners.…”