Deuterium arc lamp
A deuterium arc lamp (or simply deuterium lamp) is a low-pressure
Plasma "arc" or discharge lamps using hydrogen are notable for their high output in the ultraviolet, with comparatively little output in the visible and infrared. This is similar to the situation in a hydrogen flame. Arc lamps made with ordinary light-hydrogen (
Principle of operation
A deuterium lamp uses a
The arc created excites the molecular
The spectral line structure of deuterium does not differ noticeably from that of light hydrogen, but deuterium has a slightly stronger molecular bond (439.5 vs. 432 kJ/mol) and is less-well ionized at the temperature of the arc. This causes a larger population of molecules and a greater emissivity (light output) of UV in the molecular part of the spectrum that is farthest into the ultraviolet.[2]
Because the lamp operates at high temperatures, normal glass housings cannot be used for a casing. They would also block UV radiation. Instead, a fused quartz, UV glass, or magnesium fluoride envelope is used depending on the specific function of the lamp.[3]
The typical lifetime of a deuterium lamp is approximately 2000 hours (Most manufacturers guarantee 2000 hours, but newer lamps are consistently performing well at 5000 hours and more). [citation needed]
Deuterium lamp spectra
The deuterium lamp emits radiation extending from 112 nm to 900 nm, although its continuous spectrum is only from 180 nm to 370 nm. The spectrum intensity does not actually decrease from 250 nm to 200 nm as shown in the spectrum plot above. The decrease in the plot is due to decreased efficiency at low wavelengths of the photo detector used to measure the lamp intensity. The deuterium lamp's continuous spectrum is useful as both a reference in UV radiometric work and to generate a signal in various photometric devices.
Safety
Due to the high intensity of UV radiation emitted by the bulb, eye protection is suggested when using a deuterium bulb. Care must also be taken to avoid touching the bulb directly to avoid burns due to high operating temperatures. Touching the bulb directly even when cool could deposit impurities onto the casing that strongly absorb the short wavelength UV and therefore reduce output intensity.
References
- ^ "Deuterium Lamps" (PDF). Photron Pty Ltd. 2011-10-20. Archived from the original (PDF) on 2016-03-04. Retrieved 2011-10-20.
- ^ Paper on UV analysis which describes deuterium lamp advantage Accessed Sept 25, 2014.
- ^ "Deuterium Lamps". Photron Pty Ltd. 2011-10-20. Archived from the original on 2011-10-03. Retrieved 2011-10-20.