|
|
Lamp coupling experiment
|
Here's a little experiment I did a while ago and which consisted in illuminating a running HPI-T 400W with the intense light from a 100 W UHP lamp. Since the latter is built with a parabolic reflector, its radiation is focused. I aligned the two lamps so that point of focus coincides with the center of the HPI arc, resulting in the most effective energy transfer possible from the UHP lamp to the HPI burner. This way, the latter is heated (approximately) as if it was operating in an enclosed reflector luminaire, thus ensuring that indium and thallium iodides are fully evaporated, as intended for a HPI lamp. No all of the UHP radiation is absorbed by the burner and its plasma though, but the (faint) absorption lines of sodium, thallium, and indium (i.e., HPI's additives) can be observed in the continuous spectrum of the UHP lamp.
|
|
Forum
Gallery Home
Login
Off-Topic
Album list
Last uploads
Last comments
Most viewed
Top rated
My Favorites
Search
Tuopeek - I remember those light absorption experiments we did in high school back then. It involved a source of white light, a Bunsen burner and some sodium solution. This would work perfectly with a hot SOX lamp just after discharge extinction too. The issue, however, is that although those are the best ways to observe atomic absorption lines, they give access to resonant transitions only (transitions involving the ground state of atoms), which in most elements lie in the UV.
The idea of the experiment shown above is to get access to non-resonant transitions as atoms are excited in the plasma, thus enabling optical transitions in the visible domain from excited states. However, there is a clear problem of poor measurement/observation contrast here because of the HPI plasma's own optical emission, so that's why I resorted to using the brightest light source I could find so as to get a spectral background brighter than the spectral intensity of the HPI plasma. That's not easy to achieve, even with a UHP lamp, and that's why this kind of experiments are usually done with tunable lasers instead, but I don't have that at home... one way to improve the present experiment would be to do a phased-resolved spectral measurement. The contrast of the absorption spectrum is bound to increase when the HPI plasma is in its extinction phase as the discharge current nears the zero crossing of its AC waveshape.