ABSTRACT
I INTRODUCTION We have assembled a bench-top system for obtaining the distribution of Hg atoms in operating metal-halide high-intensity discharge (HID) lamps using the method of x-ray absorption imaging[1]. The Hg density is obtained from a two-dimensional radiograph of the x-ray transmission through the HID lamp. Cylindrical symmetry allows an Abel inversion of the projected image to retrieve the local density as a function of radial and axial location. This technique is applicable to both ceramic and fused silica lamps. The importance of the 1-Ig distribution is that it is inversely proportional to the gas temperature. Therefore, only a single temperature measurement is required to convert the density map into a gas temperature map. The absolute temperature in the core of the arc can be obtained by optical methods[2,3]. Our system is based on previously demonstrated principles[1], but utilizes more recently available technology. X-ray absorption imaging of HID lamps has also been demonstrated using synchrotron radiation[4]. Here we are seeking to extend x-ray absorption imaging using commercially-available, bench-top equipment, thereby making the technique more widely accessible. The present configuration utilizes a Ag-anode x-ray tube source, a thin phosphor for conversion of x-rays to visible radiation, and a charge-coupled device (CCD) detector for recording x-ray images projected onto the phosphor. We have specifically designed flexibility into this system with the goal of optimizing performance.
