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Ken M.

Sat May 19 2007, 12:22AM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

Last night I was messing around with a 3" piece of PVC that I usually sit atop my tesla coil with a light bulb on top of the PVC (Acts like a stand) and I had managed to produce arcs that carbonized the walling of the pipe. With seeing stoneridge research facilities(I think) Lichtenberg figure's I thought, "Hey This might work!" except 2 issues arouse, 1) PVC pipe is white and can only be seen on 1 side, 2) plexi glass is a clear insulator expect when trying to do the same process...the plexi glass starts to melt and catxch on fire producing kind of a flowering or fanning effect reather than carbonizing and making single line trails. So my questions are as follows, 1) Can PVC be purchased as a sheet say, 4x4 by x thickness?, 2)can PVC be clear like plexi glass? 3) IF the answer to #2 is no, then what insulative material is like plexi glas in being clear, but is also like PVC where it would carbonize rather than catch on fire? I have been searching on google for a lil while and so haven't found much more then standard pvc pipe

Skip Found what I was looking for

.....

...

Sat May 19 2007, 12:45AM

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

for refrence, mcmaster carr (google it) has tons of that kind of stuff

Bert

Sat May 19 2007, 02:10AM

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

You can sometimes find clear PVC, but it's somewhat uncommon and a bit pricey. Polycarbonate (Lexan) is easier to find, and it may actually work better, especially if you are able to provide some semiconducting surface contamination. You can also form similar tracking across the suface of wood if you first moisten the region between HV electrodes with water.

The following pictures show the a Lexan insulating plate from a home-brew 3-electrode spark gap (trigatron). The trigatron was previously used as the main HV swiitch on the Quarter Shrinker. Although it was (in hindsight) a poor choice of materials, I designed the device with a small piece of PVC pipe as a spacer. Unfortunately, the PVC rather quickly began tracking under HV stress. When combined with atmospheric water vapor, hydrogen chloride from the tracking PVC redeposited a semiconducting film of hydrochloric acid on the Lexan plate. This induced electrical tracking across the surface of the Lexan, creating some nice 2D Lichtenberg Figures on the surface of the Lexan.

Eventually, this led to unexpected pretriggering via surface flashovers. Since I really don't like multi-kilojoule surprises, and the trigatron required significant maintenance, I eventually replaced the trigatron with a more robust (and more reliable) solenoid-triggered gap. Even though it required significant maintenance, and provided unwanted surprises every now and then, it handled over 5,000 shots, at 4 - 6.5 kJ/shot, before finally being retired.

Ken M.

Sun May 20 2007, 05:28AM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

HAha and Bert's website is the exact one I was getting the Litchenberg Ideas from. Yes indeed Bert PVC is expensive found a us company that sells sheets, but for a 24"X48"x1" sheet was $150 and I was like no way. Yea ... I found some places that sold the stuff, hence why I edited my original post with "Skip found what I was looking for". Bert what acrylic do you guys use, if you don't mind me asking? I decided on PVC just because I like the results it provided when I used it on a piece of pvc pipe. I'll get some photos because it looks rather nice.

Bert

Sun May 20 2007, 10:51PM

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

WhiteArc wrote ...

Bert what acrylic do you guys use, if you don't mind me asking? I decided on PVC just because I like the results it provided when I used it on a piece of pvc pipe. I'll get some photos because it looks rather nice.

Dark Lichtenberg figures on white PVC look look very impressive. However, if you do make more of them, do so in a well ventilated area. The hydrogen chloride fumes that are given off are really nasty...

For our regular Lichtenberg figures, we mostly use cell-cast acrylic material from high quality suppliers. We need repeatability from piece to piece across manufacturing lots, and the parameters which are critical for us (very high electrical resistivity, minimal solarization from the ebeam) are not ones that we can specify or that are monitored/controlled by the vendors. Large acrylic manufacturers seem to have tighter material and process controls, which provides us with more consistent results. When we find a supplier whose material works well, we tend to stay with them, even if they may be more expensive than some [i] alternatives. Vendors we used in our last run included Spartech (Polycast), Cyro (Acrylite GP), and Altuglas (Atoglas).

GreySoul

Sun May 20 2007, 11:42PM

Registered Member #546 Joined: Fri Feb 23 2007, 11:43PM
Location: Albuquerque, NM
Posts: 239

Hey Bert, I've always wondered what your ebeam source is for making those beautiful figures? I can't imagine a homemade LINAC would produce the consistently repeatable results you need.

I looked around on your site once a while back and either missed or didn't see the "technical" side of what you're doing, just a sorta general description...

if you'd have to kill me after you tell me, then by all means... ssshhhhh :)

-Doug

Bert

Mon May 21 2007, 03:41PM

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

GreySoul wrote ...

Hey Bert, I've always wondered what your ebeam source is for making those beautiful figures? I can't imagine a homemade LINAC would produce the consistently repeatable results you need.

I looked around on your site once a while back and either missed or didn't see the "technical" side of what you're doing, just a sorta general description...

if you'd have to kill me after you tell me, then by all means... ssshhhhh :)

-Doug

No problem, Doug. I tried to convince the wife to let me build an accelerator, but no such luck...

We rent "beam time" on a 5 million electron volt (MeV) 150 kW commercial electron beam accelerator. The facility is normally used for materials processing (polymerizing or crosslinking of various plastics, resin beads, etc.) to alter or improve properties. Common examples are cross-linked PE tubing and wire insulation. All of the gory details of the process can be found here:

The LINAC is like a CRT on steroids, except that the accelerating voltage is between 1-5 million volts instead of 25 kV, and the ebeam is passed through a thin titanium window instead of lighting screen phosphors. The LINAC beam current is adjustable from 50 microamps to about 10 mA, and beam energies between 1 to 5 million volts are available. The ebeam is scanned electromagnetically so that it can irradiate a region that's about 4" by 48". Material to be irradiated is transported below the beam in movable carts on a track. Right underneath the feedhorn where the beam exits, there is a stainless steel water-cooled shutter that absorbs and blocks the beam. This is rotated out of the beam path prior to irradiating specimens. The process is done behind thick concrete walls because of the high energy x-radiation that's produced. Our specimens are located about 18" below the titanium window and the electrons travel this distance through air. When hit by the beam the Plexiglas specimens glow a brilliant blue-white color from a combination of fluorescence and Cherenkov radiation. Sometimes they also emit bright flashes if they prematurely discharge while being irradiated.

I'll be adding some video of the process soon from a large amount of video that Terry Blake captured during our December run. There is considerable energy deposited by whatever is hit by the ebeam. The carts are 1/4" thick aluminum, and they warm up just by being hit by the beam. The director of the facility showed us the remains of a cart that remained in one position under the beam when the beam shutter accidentally failed to close. The beam actually melted the cart in half in well under a minute...

Ken M.

Mon May 21 2007, 05:19PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

WOW

So thats why your figures are so darned expensive! But in the low cost simpler version I'm attempting, Will I always yeild Black tracings or is it possible to to yeaild clear such as yours?

Also heres the pics I said I'd add.

GreySoul

Fri Jun 01 2007, 10:03PM

Registered Member #546 Joined: Fri Feb 23 2007, 11:43PM
Location: Albuquerque, NM
Posts: 239

Bert, cool ebeam :)

So I have come to two more questions:

1. Do you or anyone else here have links to plans for a homemade LINAC? I have googled around a bit and found some rather lacking descriptions and general ideas, but nothing I've seen has evidence of a real homamde LINAC, just some brainstorms and non-functional mock ups.

2. Would a Polonium-210 needle source (alpha radiation, 5.3MeV) work as a source of energy to charge an acrylic block (or anything else, really) or would the fact that it's an omni-directional emitter eliminate it from useful experimentation in this field?

thanks for the mental dialog :)

-Doug

Bert

Sat Jun 02 2007, 03:09AM

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

GreySoul wrote ...

Bert, cool ebeam :)

So I have come to two more questions:

1. Do you or anyone else here have links to plans for a homemade LINAC? I have googled around a bit and found some rather lacking descriptions and general ideas, but nothing I've seen has evidence of a real homamde LINAC, just some brainstorms and non-functional mock ups.

From time to time I've seen folks building home brew accelerators, but I can't seem to locate them now. Some were cyclotrons, and at least a couple were LINACS using large VDG to provide high voltages. Here's a small 100 kV LINAC from Fred Niell (who also built his own cyclotron) :

There is also a pretty nice "how to" article in the January, 1959 issue of Scientific American, Amateur Scientist column, "How to Make an Electrostatic Machine to Accelerate Both Electrons and Protons" using a 300 kV Van de Graaff generator. This article (and all the other articles over a 73 year span!) is still available on CD from the following (and other sources):

The 300 keV LINAC project is also covered in C. L. Stong's book: "The Scientific American Book of Projects for The Amature Scientist", Simon & Schuster, 1960 on pages 344-360. This book may still be available via your local library inter-loan system.

Generating the high voltage is relatively easy (at least for most folks on this list). A VDG or CW generator, or perhaps even a Marx generator for a pulsed LINAC. Developing a sufficiently high vacuum may present a challenge, as well as getting the proper geometry for the accelerating tube to form the electrons into a beam. You'll also want to operate the device behind 18"-24" or so of concrete. Tungsten filaments may be harvested from light bulbs or vacuum tubes, or even purchased (tungsten filaments for electron beam microscopes). Some of the (very) gory details of accelerator design can be seen in a couple of on-line books by Stanley Humphries - "Charged Particle Beams" and "Principles of Charged Particle Acceleration". They make for excellent bedtime reading...

GreySoul wrote ...

2. Would a Polonium-210 needle source (alpha radiation, 5.3MeV) work as a source of energy to charge an acrylic block (or anything else, really) or would the fact that it's an omni-directional emitter eliminate it from useful experimentation in this field?

thanks for the mental dialog :)

-Doug

The real problem is that 5 MeV Alpha particles simply don't have much penetrating power when compared to 5MeV electrons. Even though alpha particles don't penetrate nearly as far, they are much more dangerous to work with because of the greater destruction they do within living tissues. You really want high energy electrons to make Lichtenberg Figures. Virtually all Plexiglas Lichtenberg Figures are created from either direct ebeam irradiation or indirectly from X-rays or gamma rays (via Compton scattering). BTW, its a little known fact that Lichtenberg Figures can be created within Plexiglas sheets via Compton scattering during an underground nuclear test. Another aspect of close-in EMP...

Good luck, and remember to play VERY safely when dealing with high energy electrons, protons, or X-rays, and large volumes at high vacuum... lots of ways to get damaged (sometimes without even knowing about it at the time).

Bert

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