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Two video clips about making Lichtenberg Figures on YouTube

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Bert

Mon Oct 12 2009, 12:07AM

Registered Member #118 Joined: Fri Feb 10 2006, 05:35AM
Location: Woodridge, Illinois, USA
Posts: 72

Hi all,

I recently uploaded a couple of video clips about making 2D and 3D Lichtenberg Figures on YouTube. Be sure to click on the HQ button for higher quality video.

Enjoy,

Bert

teravolt

Mon Oct 12 2009, 12:38AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

very cool, I want to make one. he must have a monopoly on them since you need 5Mv. I wonder if a big enough marx could flash acrylic like that

Nik

Mon Oct 12 2009, 01:05AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

Amazing! What is the application of the device you use to charge up the acrylic?

Bert

Mon Oct 12 2009, 01:30AM

Registered Member #118 Joined: Fri Feb 10 2006, 05:35AM
Location: Woodridge, Illinois, USA
Posts: 72

Nik wrote ...

Amazing! What is the application of the device you use to charge up the acrylic?

This particular accelerator is called a Dynamitron:

It's used for conducting polymer research (1st shift) and for industrial irradiation of polymers, such as polyethylene, polypropylene (crosslinking to improve material properties). For example, polyethylene tubing used for plumbing is irradiated by machines similar to this. Polymer resin pellets can also be irradiated prior to using them in injection molded applications. The resulting crosslinked material is mechanically tougher, melts at a higher temperature, and also has improved electrical properties. The 4-story high facility can deliver 150 kW all day long. The electron beam can be adjusted anywhere between 1 MeV to 5 MeV, and the beam current is adjustable from 10's of microamperes to 30 mA at 5 MeV, or 50 mA at 3 MeV, etc. To make Captured Lightning, we irradiate using 2.5 - 5 MeV, and some of our more complex sculptures may require three passes through the beam.

Bird-Dawg

Mon Oct 12 2009, 03:23AM

Registered Member #2360 Joined: Sun Sept 13 2009, 05:43PM
Location: Kennesaw, Ga USA
Posts: 14

What stops them from losing thier charge on the table once one is discharged? I only saw brown paper under those peices, that can't be enough to insulate them from eachother.

Scott Fusare

Mon Oct 12 2009, 10:10AM

Registered Member #531 Joined: Sat Feb 17 2007, 10:51AM
Location: Burlington, Vermont
Posts: 125

Hi Bert,

Thanks much for those videos. I absolutely love the X-ray speckle, talk about a harsh environment! One of these days I need to make the trip and see this in person.

Scott

Mates

Mon Oct 12 2009, 10:17AM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

You bastard,
You know very well where to advertise your products

Very beautiful indeed!
And thanks for the vid I was always curious how the whole thing is done...

Bert

Mon Oct 12 2009, 02:41PM

Registered Member #118 Joined: Fri Feb 10 2006, 05:35AM
Location: Woodridge, Illinois, USA
Posts: 72

Bird-Dawg wrote ...

What stops them from losing thier charge on the table once one is discharged? I only saw brown paper under those peices, that can't be enough to insulate them from eachother.

During charging, each specimen actually becomes a small, isolated high voltage capacitor. The internal layer of excess electrons forms one "plate". Positive ions, created during irradiation of the surrounding air, are strongly attracted by the negative charge within the acrylic. They form a layer of positive charge that adheres to the outer surfaces of the acylic, forming the other "plate". Plexiglas between the two charge layers forms the dielectric of this "plateless" capacitor. Even though the effective capacitance is small (~430 pF), the voltage stress between "plates" is over 2 million volts, so each 12 x 12 inch specimen can store almost 1 kilojoule of electrostatic energy. Although the stored charge leaks away slowly, there is usually plenty of working time to discharge a number of individual specimens. Because the energy is contained within each specimen and the outer surface is near ground potential, discharging one specimen has virtually no impact on neighboring specimens.

BTW, by using a Pearson wideband CT to measure discharge waveforms, we were able to determine that the main discharges propagate over 800 times faster than the speed of sound through acrylic. This is a gross violation of the standard theory of crack propagation (Griffith's Theory), which limits crack propagation velocity to the speed of sound within the material. Energy from the electrical field (internal dielectric stress) is converted into mechanical energy which "drives" propagating cracks through the material. The electrical field at the crack tips is sufficient (>20 MV/cm) to force the material immediately ahead to become electrically conductive (electronic, or "intrinsic" breakdown). The resulting positive feedback mechanism drives hypersonic crack propagation through the acrylic. This process has been termed "electronic detonation" by one team of Russian researchers from its similarity to supersonic propagation of a detonation front within high explosives. One of the few papers that is directly Internet accessible follows:

Discharging also makes a very satisfying flash and bang...

Bert

Mon Oct 12 2009, 03:18PM

Registered Member #118 Joined: Fri Feb 10 2006, 05:35AM
Location: Woodridge, Illinois, USA
Posts: 72

scott fusare wrote ...

Hi Bert,

Thanks much for those videos. I absolutely love the X-ray speckle, talk about a harsh environment! One of these days I need to make the trip and see this in person.

Scott

That could be arranged...

During the taped run, Terry Blake was able to set up an inexpensive video camera on an outer corner, behind about 1 foot of concrete. It was facing a stainless steel mirror that allowed indirect imaging of the irradiation process. A glass mirror can't be used, since the X-radiation would instantly turn it black from solarization. The shots in the video were done using a lower dosage at 3 MeV. At 5MeV, speckling was considerably worse, and included numerous little multicolored streaks. Unfortunately, the high energy X-ray flux also disrupted the autofocus circuitry of the camera (

) and it began randomly changing focus. We don't include that footage...

BTW, the camera survived the harsh treatment without any permanent damage...

Marko

Sat Oct 17 2009, 10:26PM

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

Thanks a lot for this post, this is an extremely interesting process to see.
I hope you guys watch not to get yourselves irradiated, I would be scared to get anywhere close to that building myself.

You made me remember a segment from mythbusters where they sent some food for irradiation - they seemingly used focused electron beams and no apparent shielding from generated Xrays - I thought the beams looked very cool as they ionized air on their path, but did the camera-man get cooked in the process without knowing it?
I expected to see your beam ionizing air as well, is it just to diffuse for the effect to be observable?

By the way, could you once make a footage of a glass mirror actually turning black? I'd really like to see that

Regards,

Marko

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