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Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843
I wonder, can anyone get or has anyone seen the following paper? I'm very curious about this and I'd like to find out the details.
UV LED Triggered Spark Gap Chung, M. Plasma Science, 2007. ICOPS 2007. IEEE 34th International Conference on Volume , Issue , 17-22 June 2007 Page(s):344 - 344 Digital Object Identifier 10.1109/PPPS.2007.4345650 Summary:Summary form only given. Spark gap is used extensively in all kinds of pulse generators, traditional Trigatron type spark gap relies on a pulsed high voltage (usually around 30 % of hold off voltage) to trigger the main gap breakdown. The statistical delay is inversely proportional to pressure and related to streamer propagation time. On the other hand, laser triggered spark gap require high cost YAG laser to provide very strong intensity (~109 W/cm2, tens of mJ energy) to ionize SF6 or air to initiate breakdown. UV flash lamp has also been used to trigger Thyratron in Back Light Thyratron (BLT). The emergence of high power (1-3 W) U V LED presents a new opportunity in triggering a spark gap. LED is compact, low cost, low voltage, and with very low jitter. One or several UV LEDs are positioned in the center of a Trigatron type spark gap to initiate the main discharge. Preliminary results of breakdown waveform and delay are discussed.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Yes, I remember that paper attracted quite a bit of interest when it first came out, and I think I made a post about it here at the time.
So far as I recall, the UV LED used was of quite high power and shorter wavelength, than the little LEDs sold as "UV" which are really on the cusp of long wave UV and violet.
At the time, I remember looking at the data sheet of the UV LED, which coincidentally (!) appeared on the market at the same time as this paper, and noticing that it cost some hundreds of dollars.
This is from memory, so if it is very important to you, I should still advise you to verify it elsewhere.
But the point is this: you can smell ozone strongly around short UV sources, and nothing around the little near violet LEDs - what does that tell you?
You'd have much better results, in my view, with a DIY N2 laser (X = 337.1 nm) such as that constructed by 4HV member Plazmatron.
Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843
Unfortunately the "paper" doesn't provide much information, so the details are still lacking.
I don't know what wavelength was used in the study, but I suspect it would need to be shorter than 370 nm to ionize anything or to cause photoemission from the electrode surfaces.
As Harry said, it seems the shorter wavelength UV LEDs are very expensive...so I think this approach might not be practical right now, unfortunately.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
I can't see this working until they have LEDs that are short enough wavelength to be absorbed by air. That's about 190nm or so. roughly another octave to go. How long did it take to get from red LEDs to blue ones?
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
When those 370nm UV LEDs came out, I did some sums, and they will eject electrons from sodium electrodes. Unfortunately all more practical electrode materials need more punch per photon.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
hmm. there are now 270nm LEDs but are stupidly expensive.
IIRC a standard quartz window UV LED *might* be feasible to supercool and pulse at an amp or so, you might be lucky and run into a "Freak" which emits short wave pulses, like the early GaN blue did.
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UV LED Triggered Spark gap
