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Registered Member #1034
Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154
I have produced a peculiar pink light emission form a quarts tube filled with low pressure gas excited by a coil of wire wrapped around the tube. The coil of wire is hooked up like the primary of a disruptive discharge Tesla coil using a .01 uf capacitor. To get this to work I have to use as good of a vacuum as my 2 stage mechanical pump will pull. I don't have any way to measure it but I would say it is probably around 10 microns. If I let the pressure go up a little the discharge turns white and if it goes up a little more the discharge goes away. The type of gas in the tube doesn't seem to matter.
It doesn't surprise me that I can get the gas in the tube to light up this way but why would it be pink?
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Roger -
Gary Lau obtained a very similar pink plasma discharge by simply boiling a little water in a jar, then tightly securing the lid while the jar was filled with steam. As the steam cooled and the water vapor condensed, the pressure in the jar dropped significantly, and the jar was left containing nitrogen, water vapor and a little oxygen at a low pressure.
Gary then subjected the jar to the output from his Mini TC, and generated brilliant pink plasma within.
See Gary's writeup, about 75% of the way down the page:
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Years ago, I wound a few dozen turns round a striplight, and then tuned that up with a 10W HF transmitter, and can remember the glow around the coil.
As to why your particlular discharge is pink, at a specified pressure, gaseous composition, and exciting frequency, you'd need a better plasma theorist than me! All I can say is that it is not ususual.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Uzzors wrote ...
That reminds me of lightning sprites. This guy has done something similar.
I can't explain the color either, ask a chemist.
The Aurora Borealias, or Nordlys, change colour according to their height in the atmosphere. Most often they are a pale lime green, but when they descend to a lower height, they can appear to be salmon pink, purple, or even red - all of which I have seen in February and March in Svalbard. At such low heights, when they are red, they are said to be accompanied at times by a hissing sound on quiet nights in the circum-polar North, though I haven't heard this myself.
Still, you can be sure it has to do with the energy spectrum of molecular excitation, (think: the colour temperature of light) but I'll leave it to wiser heads than mine to give a fuller explanation.
Registered Member #1034
Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154
Ok , I see that this color is not too unusual. Before I used the coil of wire I had electrodes at each end of the tube and I have excited the gas by running an electric current through it. When I do that the color is usually purplish or white or blue or some combination of those colors. That's why I was a little surprised to get pink.
When I use the coil with the Tesla circuit, I am producing very intense but brief pulses of excitation but when I run an electric current though the tube though the electrodes it is a gentile but continuous excitation. That might be why I get such a different color.
Unfortunately I haven't seen the northern lights here in central Ohio. Thanks all of you for your comments and help.
Registered Member #1389
Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346
One of my very first projects was an (oversized) CW multiplier made from flash circuits: 300VAC, 22nF 400V caps, 22 stages. I initially ran it short circuit into sparks (i know now how dumb that idea was >.>) and eventually with two large 250k 2W resistors in a plastic tube under oil. With short cirucit I got the characteristic white flash of xenon flash tubes. At lower currents and continuous DC, I got a blue or blue-white glow instead of a flash. Then, one of my resistors failed (the element broke from an arc over) and the discharge turned into many wispy green 'sparks', which I assume were made when small amounts of energy in the CW manage to bridge the gap. Thus, the color seems to be affected by pulse repetition, pulse energy, and pulse length (all the way up to DC).
I plan to reproduce the results with a string of 100Meg resistors connected to my new 36kV MOT multiplier.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Roger, if you follow up my lead to Geissler (pronounced: GUY-slur ) Tubes, (perhaps on Wikipedia to start with) which were a popular scientific 'parlour amusement' of late Victorian times, you'll see that every manner of colour effect was produced to the delight of after-dinner spectators.
It certainly has to do with the energy state of the excited gas molecules, but why 'pink' in particular is quite beyond me, I'm afraid, beyond saying that 'pink' is clearly a combination of light frequencies, or mixed photon energy states. Yours is a good question. Real science.
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Pink light emission from low pressure gas lamp
All I can say is that it is not ususual.
