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New Scientist article on ball-like floating plasmoids -ning

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Dr. Slack

Thu Jan 11 2007, 08:28AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

"Comic Cuts" (11th January 2007) might be a bit closer to something sensible this time. A group in Brazil have got floating glowing balls to last 8 seconds, by vapourising a silicon wafer in an arc, after an idea that that's what can occur when lightning hits the silicon rich ground.

ragnar

Thu Jan 11 2007, 11:34AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

/me buys pretty-looking dud silicon wafers from electronics goldmine, NOW =P

Marko

Thu Jan 11 2007, 12:49PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

THe idea is actually cool, but I think it would be good idea to remove 'ball lightning' from the title since ''real'' ball lightning behaves intelligently and creates crop circles..

About the silicon, it may burn, even brilliantly, but I think sparkles/balls/whatever are going to just fall on the flor rather than floating around.

Conundrum

Fri Jan 12 2007, 12:20PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Note- only works in Windows Media Player, in IE.

There are similar reports of an anti-missile countermeasure that show up as glowing balls in the infrared (iirc its iron oxide nanoparticles coated inside aerogel which then oxidise quickly)

Anyone know how to make thin films of silicon? :)

If this is simple to optimise I can see this being a very amusing science fair demo..

-A

Steve Conner

Fri Jan 12 2007, 01:41PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Can't someone just get some old ICs, crack the plastic off to expose the silicon die, and blast them with a cap bank? That seems like the sort of thing 4hv members would enjoy

Maybe Tesladownunder should blast some pieces of silicon in his vortex spark chamber thingy. Or maybe I should nuke a whole bunch of IGBTs... no wait, I've already done that.

Note: the moderators have been discussing 4hv's policy on this subject, and yes, we would rather that you didn't use the words "b*** l********". The reason is that we want to distance ourselves as much as possible from the guys who think it behaves intelligently and makes crop circles, etc. We certainly don't want to appear alongside them in Google searches

We suggest calling it stable plasmoids instead.

cbfull

Fri Jan 12 2007, 01:57PM

Registered Member #187 Joined: Thu Feb 16 2006, 02:54PM
Location: Central Ohio
Posts: 140

"Plasmoid" has a much nicer ring to it anyway. Sounds more scientific.

Tesladownunder

Sat Jan 13 2007, 04:40AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Steve Conner wrote ...

Can't someone just get some old ICs, crack the plastic off to expose the silicon die, and blast them with a cap bank? That seems like the sort of thing 4hv members would enjoy

Maybe Tesladownunder should blast some pieces of silicon in his vortex spark chamber thingy. Or maybe I should nuke a whole bunch of IGBTs... no wait, I've already done that.

Can't resist a challenge.
Here is 2.6g of silicon chip I have reduced to dust from an SCR that had 15kA go through it. (12.5 was OK). The SCR autopsy report is here. This is much larger than most IGBT's I imagine.

I have done a few daytime blank shots with the cap bank at 2kJ with an aluminium foil base so it should get real hot with the Al ignition, but the lighting is not ideal. I will try at dusk and if OK will try the silicon.

While I was doing this there was a big bang coming from the highway nearby. Competition? I thought. No, just a caravan tyre blowout.

Peter

...

Sat Jan 13 2007, 04:43AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

If you find your self short on silicon, I have some large (several kg) boules that the wafers would have been cut out of, and a few wafers of random stuff laying arround. I also think I have some stuff on a GaAs substrait, but it might actually be silicon...

Bjørn

Sat Jan 13 2007, 05:05AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

I have made sustained glowing spheres that would float around the floor without friction just like in the Brazilian video by igniting bits of aluminium foil. So mixing aluminium foil and silicon will make it impossible to say what is glowing.

Tesladownunder

Sat Jan 13 2007, 03:02PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

I put a gram of silicon powder and fired it with aluminium foil at 2kJ. Just a big flash. I was just about to discard the photo when I saw the green ball.
This is for real and the photo shows it clearly. I have not retouched it other than to reduce the size to fit 4HV.
It is of course a lens flare and on the image is 1452 pixels in and 514 down. The flash would be arising from 1452 pixels from the other side and about 500 pixels up - in other words diametrically opposed and confirming the flare. It was too small to be a vortex anyway and wasn't moving on the 1 second exposure. There are other lens flares pointing down which are yellow and the other is blue. Funny I haven't seen these much in photos before. Perhaps because I wasn't looking for them or because the camera was centered on the arc.
I have the video but haven't looked at the shot yet.

I confess I hadn't read the New Scientist article (although I listen to all their podcasts while cycling), so I didn't realise that they were just melting silicon in an arc. Bill Beaty pointed out this YouTube video that shows the balls bouncing around.

Perhaps I need to pull apart another SCR and try the arc welding approach as suggested here.

Actually I just realised that this pic was not from the silicon shot but from an aluminium and ethanol shot. The silicon was similar but the lens flare was still present in a different area and less visible due to the different camera position.

Peter

1168700525 10 FT19679 Pulsecapballsiliconflare

1168700525 10 FT19679 Pulsecapballsiliconflareclose

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