DRSSTCs and Long Pulse arcs (corkscrew effect)
HV Enthusiast, Sat Jul 15 2006, 01:40AMI've recently been playing around with DRSSTCs utilizing long pulse mode of operation and exploring the so called corkscrew effect of the arcs. My present system is designed to produce output arcs up to 20ms and PRFs of 20Hz with a maximum duty cycle of 40%, although i typically limit runs to 10% for obvious reasons.
Regarding the corkscrew effect, one conclusion i have come to is that this corkscrewing effect is evident regardless of the pulsewidth. Short (50us) as well as the long pulsewidths exhibit this corkscrewing effect, and the it only becomes more evident with long pulses because the arc tends to rotate more revolutions due to the longer pulsewidth and this causes an apparent increase in brightness.
I'm not sure if anyone has come up with a reason for this effect yet, but i suspect it may be due to the magnetic field created by the arc (AC current) and its causing the arc itself to rotate. From my photography, i have determined the direction of rotation is clockwise which tends to correspond with the right hand rule.
Anyways, if anyone else has some thoughts on this, or if there is an actual explanation already for this effect, i'd love to hear it.
Here are some photos of a 20ms pulsewidth long arc striking a 36" target. Note the many loops, and "knots" in the photos as well as the primary arc channel which can be clearly seen. This is a single pulse (one arc) and although the main channel appears rather straight, i suspect the "loops" actually move through out the pulse and are simply overlaying the main channel when they occur.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Bjørn, Sat Jul 15 2006, 02:27AM
Plasma has a tendency to do that at all scales from tiny discharges to gigantic structures in the universe. My guess is that it is Birkeland currents. Just currents flowing in the plasma. The current will create an opposing magnetic field that makes corkscrews and knots in the plasma.
Bjørn, Sat Jul 15 2006, 02:27AM
Plasma has a tendency to do that at all scales from tiny discharges to gigantic structures in the universe. My guess is that it is Birkeland currents. Just currents flowing in the plasma. The current will create an opposing magnetic field that makes corkscrews and knots in the plasma.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Dr. Drone, Sat Jul 15 2006, 02:28AM
Dr. Drone, Sat Jul 15 2006, 02:28AM
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
HV Enthusiast, Sat Jul 15 2006, 03:20AM
Thanks. Looks like it just might be a contact area where the arc is hitting. If you look vertically to that, there seems to be some sort of boundary where the arcs seem to stop and this weird squiggley thing is right on it. There is a similar one down below. Thats just my guess.
HV Enthusiast, Sat Jul 15 2006, 03:20AM
Thanks. Looks like it just might be a contact area where the arc is hitting. If you look vertically to that, there seems to be some sort of boundary where the arcs seem to stop and this weird squiggley thing is right on it. There is a similar one down below. Thats just my guess.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
..., Sat Jul 15 2006, 05:04AM
You had me for a second with that first pic, until I clicked on it I thought you actually had a spark that had the red line down the center
In any case, those are some pretty awesome pics 
I almost doubt that the corkscrew is from the plasma's magnetic feild, as I remember seing a pic looking in line with the ark off a marx generator that looked alot like your sparks do (not as fat of course)
@chris
I would almost put money on that little corkscrew thing was a bug that flew past the coil, got struck, then started to corkscrew arround
..., Sat Jul 15 2006, 05:04AM
You had me for a second with that first pic, until I clicked on it I thought you actually had a spark that had the red line down the center
In any case, those are some pretty awesome pics I almost doubt that the corkscrew is from the plasma's magnetic feild, as I remember seing a pic looking in line with the ark off a marx generator that looked alot like your sparks do (not as fat of course)@chris
I would almost put money on that little corkscrew thing was a bug that flew past the coil, got struck, then started to corkscrew arround
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Steve Ward, Sat Jul 15 2006, 06:19AM
So the spark from a marx doesnt produce a b-field around it? huh...
Dan:
I think we really need some high speed camera's to see exactly what is going on with the corkscrew production. I noticed that when i got my coil up to 5' sparks like that, the effect was even more pronounced. My mental image was that it was simply corona "growing" on the base streamer, but as to why it corkscrews, i had no idea. I agree that its likely its own b-field distorting the path, but i wonder about discharges between say 2 large spheres, where the arc is almost completely straight. And also, the B-field should be oscillating back and forth at a rather high frequency, so im not sure i see why it would only rotate in one direction over the other.
It seems that VTTCs produce a much more uniform effect. But sometimes the oddness of the SSTC sparks are more interesting to look at .
Oh, and fantastic pictures btw.
Steve Ward, Sat Jul 15 2006, 06:19AM
I almost doubt that the corkscrew is from the plasma's magnetic feild, as I remember seing a pic looking in line with the ark off a marx generator that looked alot like your sparks do (not as fat of course)
So the spark from a marx doesnt produce a b-field around it? huh...
Dan:
I think we really need some high speed camera's to see exactly what is going on with the corkscrew production. I noticed that when i got my coil up to 5' sparks like that, the effect was even more pronounced. My mental image was that it was simply corona "growing" on the base streamer, but as to why it corkscrews, i had no idea. I agree that its likely its own b-field distorting the path, but i wonder about discharges between say 2 large spheres, where the arc is almost completely straight. And also, the B-field should be oscillating back and forth at a rather high frequency, so im not sure i see why it would only rotate in one direction over the other.
It seems that VTTCs produce a much more uniform effect. But sometimes the oddness of the SSTC sparks are more interesting to look at
.Oh, and fantastic pictures btw.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Bjørn, Sat Jul 15 2006, 06:26AM
Bjørn, Sat Jul 15 2006, 06:26AM
Hey, can you tell me what this is as I wonder if it is the cork thingy? It just appeared and went away?The tiny corkscrew seems to be part of something larger that did not record completely on the picture. You can see that the camera has moved during the exposure and that there is a line of missing arc segments to the left of the bar. So it is not possible to say it it is a corkscrew or not from the photograph.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Reaching, Sat Jul 15 2006, 11:33AM
if you convert a pic to negative you can notice this effect on most every pic of sstcs,drsstcs and vttcs. i think it has to do with the big E-M field of an arc induced back in the secondary coil which modulates the almost sinusodial waveform to a much more complex one which is part of this corkscrew effect.
Negative
normal
i looked at a few of my pics and noticed this effect on every of my drsstcs and sstcs independend of dutycycle,pulsewidth etc
another thought, it has to do with air flow between the hot plasma, .if you have a look at this corkscrew in detail you can see that it consists of many streamers with nearly the same distance to each other but with the same direction and corkscrew appearance. maybe the hot air is circulating between this arc which causes the plasma to rotate on the air flow, just a thought
Reaching, Sat Jul 15 2006, 11:33AM
if you convert a pic to negative you can notice this effect on most every pic of sstcs,drsstcs and vttcs. i think it has to do with the big E-M field of an arc induced back in the secondary coil which modulates the almost sinusodial waveform to a much more complex one which is part of this corkscrew effect.
Negative
normali looked at a few of my pics and noticed this effect on every of my drsstcs and sstcs independend of dutycycle,pulsewidth etc
another thought, it has to do with air flow between the hot plasma, .if you have a look at this corkscrew in detail you can see that it consists of many streamers with nearly the same distance to each other but with the same direction and corkscrew appearance. maybe the hot air is circulating between this arc which causes the plasma to rotate on the air flow, just a thought
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
..., Sat Jul 15 2006, 02:09PM
@steve ward
my logic was that the spark from a marx doesn't 'grow' like a tesla coil, which is running current through the streamer all of the times (and cuasing a magnetic feild around it) that gives it the corkscrew appearance. The marx spark spark doesn't have very much energy running through it until is is fully formed, so it couldn't have formed as a corkscrew from its own magnetic field.
..., Sat Jul 15 2006, 02:09PM
@steve ward
my logic was that the spark from a marx doesn't 'grow' like a tesla coil, which is running current through the streamer all of the times (and cuasing a magnetic feild around it) that gives it the corkscrew appearance. The marx spark spark doesn't have very much energy running through it until is is fully formed, so it couldn't have formed as a corkscrew from its own magnetic field.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
HV Enthusiast, Sat Jul 15 2006, 05:32PM
Thanks for the comments. Good information regarding the Birkeland currents. I never heard of that term before.
Steve,
I never thought about corona forming from the arc itself, but that is an interesting observation, at least visually.
Regarding high speed photography, i don't have access to a high speed video camera, but do have a Canon 50mm f/1.0L lense which is one of the fastest 35mm lenses ever made.
I may try taking some shots with this (i can probably shoot at f/1.0 and up to 1/2000 or 1/4000th) and still get a good exposure of the arc. This way, i can get a closer look to actual streamer channel and see what happens on a smaller time scale. Still even 1/1000 is stilll only 100us, quite long. Maybe a better example would be to shorten the pulsewidth and use that to control the exposure, except now arc length will be relatively short.
Any moving distribution of charges causes a magnetic field. This includes the discharge from a marx generator.
HV Enthusiast, Sat Jul 15 2006, 05:32PM
Thanks for the comments. Good information regarding the Birkeland currents. I never heard of that term before.
Steve,
I never thought about corona forming from the arc itself, but that is an interesting observation, at least visually.
Regarding high speed photography, i don't have access to a high speed video camera, but do have a Canon 50mm f/1.0L lense which is one of the fastest 35mm lenses ever made.
I may try taking some shots with this (i can probably shoot at f/1.0 and up to 1/2000 or 1/4000th) and still get a good exposure of the arc. This way, i can get a closer look to actual streamer channel and see what happens on a smaller time scale. Still even 1/1000 is stilll only 100us, quite long. Maybe a better example would be to shorten the pulsewidth and use that to control the exposure, except now arc length will be relatively short.
... wrote ...
@steve ward
my logic was that the spark from a marx doesn't 'grow' like a tesla coil, which is running current through the streamer all of the times (and cuasing a magnetic feild around it) that gives it the corkscrew appearance. The marx spark spark doesn't have very much energy running through it until is is fully formed, so it couldn't have formed as a corkscrew from its own magnetic field.
@steve ward
my logic was that the spark from a marx doesn't 'grow' like a tesla coil, which is running current through the streamer all of the times (and cuasing a magnetic feild around it) that gives it the corkscrew appearance. The marx spark spark doesn't have very much energy running through it until is is fully formed, so it couldn't have formed as a corkscrew from its own magnetic field.
Any moving distribution of charges causes a magnetic field. This includes the discharge from a marx generator.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Terry Fritz, Sat Jul 15 2006, 09:01PM
Hi Dan,
Wonderful pictures and data!!! They make cool screen backgrounds
I have tries using a super powerful magnet to fiddle with the corkscrews on a tube coil. I'll quote a post about it here:
""""""""""""""""""""""
Hi,
I tried a little test today.
I went to the local magnet deli and got a large 2.5 inch dia 1/2 inch thick
round magnet with a 3/4 inch center hole:
It is the NdFeB type and rated at 1.21T
This magnet sets happily on my tube coil:
So how does it affect the corkscrewing?
Without:
With:
It is hard to tell from the pictures, but as far as I can see first hand,
it makes no difference at all... Flipping the magnet to the other side did
not affect anything.
Maybe this will mean something to somebody...
Cheers,
Terry
""""""""""""""""""""""""
So I never saw in great effects from the magnet... I was sort of thinking the corkscrew has something to do with heat...
My little test was not real conclusive or anything but I thought I would mention it.
Cheers,
Terry
Terry Fritz, Sat Jul 15 2006, 09:01PM
Hi Dan,
Wonderful pictures and data!!! They make cool screen backgrounds
I have tries using a super powerful magnet to fiddle with the corkscrews on a tube coil. I'll quote a post about it here:
""""""""""""""""""""""
Hi,
I tried a little test today.
I went to the local magnet deli and got a large 2.5 inch dia 1/2 inch thick
round magnet with a 3/4 inch center hole:
It is the NdFeB type and rated at 1.21T
This magnet sets happily on my tube coil:
So how does it affect the corkscrewing?
Without:
With:
It is hard to tell from the pictures, but as far as I can see first hand,
it makes no difference at all... Flipping the magnet to the other side did
not affect anything.
Maybe this will mean something to somebody...
Cheers,
Terry
""""""""""""""""""""""""
So I never saw in great effects from the magnet... I was sort of thinking the corkscrew has something to do with heat...
My little test was not real conclusive or anything but I thought I would mention it.
Cheers,
Terry
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
HV Enthusiast, Sat Jul 15 2006, 11:29PM
Very interesting Terry. Do you know if anyone has done any actual research into this phenomenon and published data over the years? I know that Bjorn mentioned the Birkeland stuff, but didn't know if you knew of some actual papers on the subject.
HV Enthusiast, Sat Jul 15 2006, 11:29PM
Very interesting Terry. Do you know if anyone has done any actual research into this phenomenon and published data over the years? I know that Bjorn mentioned the Birkeland stuff, but didn't know if you knew of some actual papers on the subject.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Terry Fritz, Sun Jul 16 2006, 01:02AM
Hi Dan,
Although the effect is commonly obsserved, I don't know of any "offical" real science papers on it.
I should note that I found these pictures:
Which do show the powerful magnet deflecting the streamers. So maybe my little experiment was just not setup right to really detect anything.
Electronis traveling in a magnetic field do travel in a corscrew path if that means anything here:
Cheers,
Terry
Terry Fritz, Sun Jul 16 2006, 01:02AM
Hi Dan,
Although the effect is commonly obsserved, I don't know of any "offical" real science papers on it.
I should note that I found these pictures:
Which do show the powerful magnet deflecting the streamers. So maybe my little experiment was just not setup right to really detect anything.
Electronis traveling in a magnetic field do travel in a corscrew path if that means anything here:
Cheers,
Terry
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Bjørn, Sun Jul 16 2006, 03:24AM
Birkeland wrote a large amount of articles about plasma and how it behaves. Most of it based on experiments, even today math is not very suitable for explaining plasma behaviour. The articles are hard to find and mostly written in French.
There are many articles to find about Birkeland (field-aligned) currents in plasma but they often focus on one particular application like solar prominences. American Scientist, march-april 2000 has one such article.
Bjørn, Sun Jul 16 2006, 03:24AM
Birkeland wrote a large amount of articles about plasma and how it behaves. Most of it based on experiments, even today math is not very suitable for explaining plasma behaviour. The articles are hard to find and mostly written in French.
There are many articles to find about Birkeland (field-aligned) currents in plasma but they often focus on one particular application like solar prominences. American Scientist, march-april 2000 has one such article.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Tom540, Sun Jul 16 2006, 05:21AM
Try hanging the magnet right over it. See if the sparks bend around it or try to bend around it.
Tom540, Sun Jul 16 2006, 05:21AM
Try hanging the magnet right over it. See if the sparks bend around it or try to bend around it.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Marko, Sun Jul 16 2006, 11:44AM
If I remember correctly such magnets can be used to generate vortexes of plasma, but it worked only with DC arcs.
Magnet was put under water (smooth conductive surface) and breakout point was set rom above.
TC frequency may just be too high for any effect to be observd. (?)
Cockscrew effects may ocur in plasma's altering magnetic field but not necessaryly affected using permanent magnets (??).
And I may be just talking crap also.
Marko, Sun Jul 16 2006, 11:44AM
If I remember correctly such magnets can be used to generate vortexes of plasma, but it worked only with DC arcs.
Magnet was put under water (smooth conductive surface) and breakout point was set rom above.
TC frequency may just be too high for any effect to be observd. (?)
Cockscrew effects may ocur in plasma's altering magnetic field but not necessaryly affected using permanent magnets (??).
And I may be just talking crap also.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Coronafix, Mon Jul 17 2006, 03:30AM
There is always this picture.
Coronafix, Mon Jul 17 2006, 03:30AM
There is always this picture.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
ragnar, Mon Jul 17 2006, 04:22AM
That looks suspiciously like crappy breakout on two helical wires with a similarly crappy long exposure =P
ragnar, Mon Jul 17 2006, 04:22AM
That looks suspiciously like crappy breakout on two helical wires with a similarly crappy long exposure =P
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Coronafix, Mon Jul 17 2006, 06:52AM
You could be right. I don't know. It does say 1 min long exposure. Here is a bit of psuedoinfo on it.
Coronafix, Mon Jul 17 2006, 06:52AM
You could be right. I don't know. It does say 1 min long exposure. Here is a bit of psuedoinfo on it.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
ragnar, Mon Jul 17 2006, 07:12AM
Wow, I can't believe I just read that.
..still, the helical discharge is very pretty. I'm gonna bend some wires into that shape and make them spray corona, it looked funky. Might make a good high-res photograph (if I had a high-res camera, HA) =)
TDU, I know you've got a pic of a plasma discharge inside a tube distorted by a big speaker magnet... I've never been sure if it was because of the presence of the field, or the capacitive effect of a big metallish object against the glass?
These are interesting (and not pseudosciencey, bonus! hehe) too:
contorted plasma fun at Mike's electric stuff
ragnar, Mon Jul 17 2006, 07:12AM
Wow, I can't believe I just read that.
..still, the helical discharge is very pretty. I'm gonna bend some wires into that shape and make them spray corona, it looked funky. Might make a good high-res photograph (if I had a high-res camera, HA) =)
TDU, I know you've got a pic of a plasma discharge inside a tube distorted by a big speaker magnet... I've never been sure if it was because of the presence of the field, or the capacitive effect of a big metallish object against the glass?
These are interesting (and not pseudosciencey, bonus! hehe) too:
contorted plasma fun at Mike's electric stuff
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Nik, Mon Jul 17 2006, 08:21AM
AH! I just rememberd a photo I took of a flyback arc in a xenon flash tube, the arc spiraled around the inside of the tube from one end to the other. The reflection makes it look like a double helix but it is infact just one.
The arc stayed in that corkscrew shape until I moved or any one else came close, but the important part is there were no perminant magnets, its HF AC and its a corkscrew.
Nik, Mon Jul 17 2006, 08:21AM
AH! I just rememberd a photo I took of a flyback arc in a xenon flash tube, the arc spiraled around the inside of the tube from one end to the other. The reflection makes it look like a double helix but it is infact just one.
The arc stayed in that corkscrew shape until I moved or any one else came close, but the important part is there were no perminant magnets, its HF AC and its a corkscrew.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Avalanche, Mon Jul 17 2006, 08:57AM
I've seen that double helix photo before, but never got around to trying it. Shouldn't be that hard to validate, I would guess if it is real the helix is caused by field shaping or something. It looks very low power though, there are no streamers considering the exposure time. There's no real info to go by, like size or anything but I might give it a try.
Avalanche, Mon Jul 17 2006, 08:57AM
I've seen that double helix photo before, but never got around to trying it. Shouldn't be that hard to validate, I would guess if it is real the helix is caused by field shaping or something. It looks very low power though, there are no streamers considering the exposure time. There's no real info to go by, like size or anything but I might give it a try.
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Tesladownunder, Mon Jul 17 2006, 09:41AM
A magnet would act differently and tend to split the streamer however the action of the heated channel probably overwhelms and nullify the effect which is why we dont see it much.
Peter
Tesladownunder, Mon Jul 17 2006, 09:41AM
Terry Fritz wrote ...
.. Although the effect is commonly obsserved, I don't know of any "offical" real science papers on it. I should note that I found these pictures:
Which do show the powerful magnet deflecting the streamers. So maybe my little experiment was just not setup right to really detect anything...
This photo looks to me to simple field repulsion and nothing to do with magnetism on an AC streamer. Take the magnet and leave the foil wrapper in place and I believe it would look the same. This is the same as a corona ring effect on inhibiting adjacent sparks... Although the effect is commonly obsserved, I don't know of any "offical" real science papers on it. I should note that I found these pictures:
Which do show the powerful magnet deflecting the streamers. So maybe my little experiment was just not setup right to really detect anything...
A magnet would act differently and tend to split the streamer however the action of the heated channel probably overwhelms and nullify the effect which is why we dont see it much.
blackplasma wrote ...
Wow, I can't believe I just read that.
...TDU, I know you've got a pic of a plasma discharge inside a tube distorted by a big speaker magnet... I've never been sure if it was because of the presence of the field, or the capacitive effect of a big metallish object against the glass?....
Its a magnetic effect. The physics dept has one that makes a beam turn full circle as a demo. Thats how they bend beams for synchrotrons and linear accelerators before they get to the linear part Wow, I can't believe I just read that.
...TDU, I know you've got a pic of a plasma discharge inside a tube distorted by a big speaker magnet... I've never been sure if it was because of the presence of the field, or the capacitive effect of a big metallish object against the glass?....
Peter
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Avalanche, Mon Jul 17 2006, 10:03AM
Ok, I tried the pyramid thing to see if I could get a corkscrew / double helix type effect.
The results are pretty much inconclusive, although it does seem to make the discharge point upwards in a straight line as opposed to bushing out. Coil is my maplin coil in CW mode, with about 12 volts on the bridge, 15 second exposure.
Doesn't really prove much, as it was only a 5 minute job - uses aluminium tape, random angles, and 3 sides
Avalanche, Mon Jul 17 2006, 10:03AM
Ok, I tried the pyramid thing to see if I could get a corkscrew / double helix type effect.
The results are pretty much inconclusive, although it does seem to make the discharge point upwards in a straight line as opposed to bushing out. Coil is my maplin coil in CW mode, with about 12 volts on the bridge, 15 second exposure.
Doesn't really prove much, as it was only a 5 minute job - uses aluminium tape, random angles, and 3 sides
Re: DRSSTCs and Long Pulse arcs (corkscrew effect)
Coronafix, Mon Jul 17 2006, 11:20AM
I'd say that it would have to be the same geometry as the great pyramid. I also seem to remember that it said somewhere that the coil was in a vacuum.
Not so easy there if that is so.
But interesting to note that the "corkscrew" effect could possible be controlled to a full spiral, if of course the picture has validity.
All I know is that it has been on the net for a long time with not much info other than the keelynet article.
[Edit: Slight tweak]
Coronafix, Mon Jul 17 2006, 11:20AM
I'd say that it would have to be the same geometry as the great pyramid. I also seem to remember that it said somewhere that the coil was in a vacuum.
Not so easy there if that is so.
But interesting to note that the "corkscrew" effect could possible be controlled to a full spiral, if of course the picture has validity.
All I know is that it has been on the net for a long time with not much info other than the keelynet article.
[Edit: Slight tweak]
Print this page