We investigated upgrading the quartz glass quality from doped natural to doped synthetic quartz glass, to increase UV output at end of lamp life (EOLL), and the corresponding lamp efficiency. The key advantage is the higher transmission of doped synthetic quartz at 254 nm compared to natural quartz, which is affected by structural impurities in the bulk.
Over lifetime, the mechanisms of further defect formation are stronger in natural quartz (e.g. E’ formation of color centers at 215 nm with a wide effecting wavelength width), Advantageously, synthetic quartz is effected less, and it even recovers from initial, smaller E’ defects (215 nm) and non-bridging oxygen hole center formation (NBOH at 265 nm). This suggests a less intense degradation over lifetime for synthetic quartz. These improvements are accompanied by high-quality long-lifetime coatings to boost the overall result.
This results in a higher UV quantum yield for each lamp with less radiation losses in the quartz glass.
The solution is valid for the full power range of low-pressure UV lamps up to 1,000 W.