Pulse modulated high-pressure caesium discharge lamp

Abstract

The high-pressure caesium discharge has a favourable spectraldistribution consisting of a smooth recombination continuum in the visiblerange. When operated on a continuous power source, the spectrum in thevisible region is close to blackbody radiation; however, the lamp efficacyis restrained by the self-reversed resonance lines occurring at 825 nm and894 nm. Pulse modulation significantly increases the core plasmatemperature, suppresses the near-infrared segment of the spectrum, stronglyenhances the continuous radiation in the visible region, and successfullyavoids overloading (<40 W cm-2) the arc tubes. Thespectrum in the visible appears to have the same shape as blackbodyradiation when the lamp is operated on a multiple pulse modulated powersource.The arc tube geometry, caesium/mercury compositions, and power supplywaveforms were optimized for photometric performance through a series ofcomparison tests. The lamp efficacy increased with narrower diameter arctubes, higher lamp currents, as well as higher current crest factors (ratioof current pulse peak to RMS current). The highest efficacy achieved forthe lamp operated on the pulse modulated power supply was 46 lpw. The lampexhibits excellent dimming characteristics and has a colour rendering index(CRI) very close to a thermal source such as a tungsten halogen lamp.This study provides a framework for the design of a new lamp/ballast systemwhich features excellent dimming characteristics, a near-perfect CRI, anefficacy above 40 lpw, and long life. The application for this light sourcecould be a replacement for a high-end tungsten halogen or a whitehigh-pressure sodium lamp.