William J. Heward

Distribution of chlorine in quartz determined by neutron beam focusing prompt gamma activation analysis and micro-x-ray fluorescence

This paper describes two spatially resolved analytical techniques for chlorine distribution analysis in high-purity quartz glass. The first, prompt gamma activation analysis (PGAA), to which most of this paper is devoted,is emphasized because a new neutron focusing technique has made this study feasible. Despite the low concentration of chlorine, the neutron absorption cross section for Cl is about 200 times greater than for Si, making Cl in Si an ideal system for PGAA. The second technique described is micro-x-ray fluorescence using a laboratory-based spectrometer. The results from each technique and their ability to quantify low levels of chlorine (400-1800 μg Cl/g SiO 2 ) are described.

Phosphor Systems for Illumination Quality Solid State Lighting Products

The objective of this program is to develop phosphor systems that will enable LED lamps with 96 lm/W efficacy at correlated color temperatures, (CCTs) ~3000 K, and color rendering indices (CRIs) >80 and 71 lm/W efficacy at CCT<3100 K and CRI~95 using phosphor downconversion of LEDs. This primarily involves the invention and development of new phosphor materials that have improved efficiency and better match the eye sensitivity curves.