Low pressure (LP); Medium pressure (MP); High pressure (HP); Ozone (O3)
This categorization is due to the emission spectrum or power consumption or any other parameter? (Usually in literature it is mentioned that LP is 254 nm and MP is 200-600 nm. However, I found this definitions are bit unusual expressions. In case of scientific communications, is there a better categorization of expressions?)
Some literature has mentioned that the MP and HP lamps could produce Ozone (O3) when those are applied in water treatment. In that case can those O3 also act as an disinfectant?
In case of UV-LEDs, how are they defined? Are those LP, MP & HP based definitions are applicable?
The term pressure is referred to the mercury pressure present in the lamps : Low-pressure lamps operate with mercury vapor pressure ranging from about 100 to 1000 Pa; a buffer gas supplements the mercury vapor; Medium-pressure lamps operate with mercury vapor pressure of approximately 10 kPa, which enables this type of lamp to reach electrical power levels 100 times higher than low-pressure lamps, i.e. several tens of W/cm;
Low and high pressure lamps are monochromatic (254 nm) and medium pressure lamps are polychromatic.
As regards ozone, it is necessary that the lamps are not equipped with a doped quartz sleeve allowing thus to have wavelengths below 200 nm. these wavelengh (below 200 nm) enable dissociation of H2O into HO° radicals and further reaction between HO° and O2 allows production of O3.
As regards UV-LEDs, each of them are only monochromatic (see for example one of our paper : Effect of coupled UV-A and UV-C LEDs on both microbiological and chemical pollution of urban wastewaters. Science of the Total Environment, 426, 304-310, 2012).
Dear Jean-Luc Boudenne, Many thanks for your informative answer.
Then, in case of UV-LEDs comparisons with conventional LP and HP lamps, do the best way is actinometry based measurments of luminous flux emitted by each lamp and express in Watts?
Yes I think chemical actinometry (e.g. potassium ferroxialate) is the best method to compare fluence of UV-Led and UV-lamp. Indeed, most of commercially-available UV sensors are developped to measure fluence at 254 nm.
Best regards
Dear colleagues, at the present time there are very good Japanese UV power meter produced by the Hamamatsu Photonics
http://www.hamamatsu.com/us/en/product/category/5001/3037/index.html.
We use such UV power meter in our laboratory. And you forget about a new class of UV-light sources - excimer lamps (excilamps)
http://www.hcei.tsc.ru/en/cat/technologies/tech10.html
With kind regard,
Dr. S. Avdeev
Dear colleagues,
thanks for stating that interesting question and giving suitable answers. From my point of view, it is of highest importance to consider which wavelength range is the most important for the intended application. For instance, lacquer is cured with rather long wavelengths while the peak of the work function for disinfection is close to 254 nm - which is the peak of mercury lamps.
If ozone production is in focus, it should be mentioned that O3 is generated by mercury lamps not with the radiation peak at 254 nm. In fact, this wavelength destroys O3, while the secondary peak of mercury lamps radiating at around 180 nm produces O3. As correctly stated by Jean-Luc Boudenne, you need lamps that are not UVC-blind, e.g. need to be made of high purity quartz glass.
Please take a look in my dissertation, page 25, where you find a chart on wavelengths ...
Thesis Resonant Behaviour of Pulse Generators for the Efficient Dri...
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