HV source for Lichtenberg figure / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

HV source for Lichtenberg figure

Move Thread

LAN_403

mmt

Mon Oct 08 2012, 09:06AM

Registered Member #2333 Joined: Thu Sept 03 2009, 03:04PM
Location: Slovakia
Posts: 80

Hi, What kind of HV source is suitable for making Lichtenberg figures?
I have available these souces: tesla coil, ZVS, and 10kV 50Hz small NTS

thx :)

Daedronus

Mon Oct 08 2012, 10:05AM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
Location:
Posts: 370

from what i have seen none of them will work....
maybe electrostatic?

mmt

Mon Oct 08 2012, 12:51PM

Registered Member #2333 Joined: Thu Sept 03 2009, 03:04PM
Location: Slovakia
Posts: 80

van de graaff ? or stored low frequency HV in capacitor bank?

Pinky's Brain

Mon Oct 08 2012, 05:18PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

They use particle accelerators to inject the electrons, probably a linac at that. Which can generally achieve much higher beam energy than electrostatic accelerators. Making the DC high voltage generator would be the easier part of making the electrostatic accelerator any way ... and you'd need MV range voltages.

I'm still wondering if you couldn't charge a resin by stirring it on top of a high voltage electrode before polymerizing.

Antonio

Tue Oct 09 2012, 12:55AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

The acrylic version is a modern form of the Lichtenberg figure, that requires sofisticated equipment (apparently). The classical figures (XVIII century) require only a modest DC high-voltage source. A "ZVS" with a rectified flyback transformer may work. Just touch the HV terminal to a clean insulating plate and spread some fine powder over the area. The classical powders were of sulfur and minium. Other powders, maybe talcum, may work. The powder adheres to the charged areas making a figure. Positive and negative charges produce different patterns, and attract different powders.
See this:

Bert

Sun Oct 14 2012, 03:49PM

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

mmt wrote ...

Hi, What kind of HV source is suitable for making Lichtenberg figures?
I have available these souces: tesla coil, ZVS, and 10kV 50Hz small NTS

thx :)

Although 3D acrylic Lichtenberg figures require injecting electrons via a particle accelerator, you can easily make 2D surface figures on wood or paper by moistening the surface with salt water and then applying high voltage from an NST to a pair of separated electrodes. Heat from the electrical current flowing across the surface chars small paths and evaporates the conductive fluid. The result is charred tracking patterns that resemble Lichtenberg figures. Search "Fractal Wood Burning" on YouTube to see some examples.

You can also create 3D branching coral-like fulgurites that look similar to Lichtenberg figures by using moistened silica sand and a high current HV source such as a bank of paralleled NST's or a distribution transformer. Although fragile, they are still quite beautiful:

Surface "dust figures" are also easily made. Take a thin sheet of PVC, acrylic, polycarbonate, polypropylene, polystyrene, or Mylar and place it over a flat metal plate. All of these have high surface resistance (for surface charge retention) and high bulk dielectric strength. Connect one end of a HV DC source to the plate and the other end to a pointed wire that can be safely moved above the surface of the dielectric. Apply HV to the wire and bring the point close to the top of the dielectric sheet until you hear the little snaps of electrical discharges between the wire and the dielectric surface. The small sparks spread across the surface of the dielectric, leaving behind trapped surface charges on the sheet. Sprinkling a light dusting of various powders (such as lycopodium, sulfur, jeweler's rouge, or a rosin bag used for gymnastics and weight training) makes the resulting surface charge patterns appear. Powdered laser toner will also work, but the black dust can be very messy. I've found that inexpensive natural gray PVC sheet works nicely. It's has excellent surface resistance, and its dark gray color provides nice contrast for lighter colored powders. In the winter, you can simply brush the top surface of the PVC with your arm or a piece of fur, then hold a nail above the sheet to create multiple electrostatic sparks to create a complex variety of figures on the sheet. A pulsed HV source, such as a Marx or CW (through a spark gap) can also be used to create a single positive or negative Lichtenberg figure on the sheet. Even a piezoelectric charcoal lighter can be modified to generate HV pulses to create surface figures on thinner dielectric sheets.

Pinky's Brain

Sun Oct 14 2012, 04:36PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

Bert wrote ...
Although 3D acrylic Lichtenberg figures require injecting electrons via a particle accelerator

What's the effective voltage these accelerators bring the acrylic at?

Would it be possible to use corona charging to put a similar space charge in a stirred liquid resin before polymerizing it? There are very few garden shed LINACs, but semi-amateurs have built MV range bipolar Marx towers.

Bert

Sun Oct 14 2012, 06:41PM

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

Pinky's Brain wrote ...

Bert wrote ...
Although 3D acrylic Lichtenberg figures require injecting electrons via a particle accelerator

The estimated potential of the internal space charge regions for our specimens ranges from about 1 MV to 2.5MV. We use a beam of electrons accelerated to 2 - 5 million electron volts (MeV).

Instead of using an accelerator, space charge can be injected into solid dielectrics using short high voltage pulses and a sharpened needle. Unfortunately, the resulting trees tend to be relatively short. To develop long trees, more space charge is required. Or, a large number of successive HV pulses to grow the tree via a series of partial discharges. By using sharpened points, only moderately high peak voltages (less than 100 kV) are required. Once trees are initially formed, continued growth can be done via partial discharges using line-frequency HV AC, repetitive unipolar pulses, or RF.

I suspect it will be difficult to inject and store sufficient charge in an uncured liquid polymer so that it can be discharged after curing. All of the clear polymers I'm familiar with evolve significant heat during polymerization. Higher electron and hole mobilities in liquids or solids at higher temperatures significantly reduce the bulk resistivity of the polymer, allowing trapped space charges to leak away relatively quickly. We see significant differences in charge retention times between warm solid PMMA specimens (3 - 10 minutes at 70 - 80 degrees F), chilled (~15 - 60 minutes at 50-60 degrees F). And, specimens irradiated and kept at dry ice temperatures will retain their charge for many months! Perhaps chilling and charging uncured polymer and keeping the temperature low during polymerization might work...

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob