What are Lichtenberg Figures, and how do we create them?
(Last updated 07/03/09)
Doubly Irradiated "Windblown Lightning" Sculpture
This Captured Lightning® sculpture
was created by irradiating a block of acrylic (Plexiglas) by a beam of
electrons from a 5 million
volt particle accelerator. The electron beam irradiated the left side,
the specimen was then rotated 180 degrees,
and irradiated once more on the opposite side. This created two
independent layers of electrical charge deep inside the specimen. The
rightmost charge layer was then manually discharged, creating a
miniature "lightning storm" within the layer above. Additional electrical discharges then grew between
the two charge layers, forming a beautiful 3D discharge pattern. The
sculpture is lit from below by blue
LED's. Unlike low resolution laser crystal art, each specimen
contain a unique, and incredibly detailed, natural fractal discharge
pattern. No two Captured Lightning® sculptures are identical. As
they
branch, the branching discharge channels become increasingly finer and
hairlike, eventually disappearing at the tips. The
smallest discharges may ultimately go to the molecular level.
(Actual size: 3" x 3" x 2")
What Are Lichtenberg figures? Our Captured Lightning® sculptures are technically known as "Lichtenberg Figures".
Lichtenberg figures are branching, tree-like or fern-like patterns that
are created by high voltage discharges on the surface of, or within,
electrical insulating materials (dielectrics). The first Lichtenberg figures were actually
2-dimensional patterns formed in dust on the surface of charged insulating plates
in the laboratory of their discoverer, German physicist Georg Christoph Lichtenberg (1742-1799. Professor Lichtenberg made
this observation in the late 1700's, demonstrating
the phenomenon to his physics students and peers, and is reported in
his memoir: Super nova methodo naturam ac motum fluidi electrici
investigandi (Göttinger Novi Commentarii, Göttingen, 1777).
The basic principles
involved in the formation of these electrostatic figures later evolved
to become modern xerography and the science of plasma physics.
Lichtenberg used electrostatic devices to charge the surfaces
of various insulating materials such as resin, glass, or ebonite. He
then
sprinkled a mixture of finely powdered sulfur and red lead (lead
tetroxide) onto the surface. The powdered sulfur was attracted to the
positively charged regions and the red lead to negative regions,
thus making the previously hidden regions of charge clearly visible.
Lichtenberg
also observed that the shapes of the positively and negatively
charged figures were significantly different. Positive figures tended to be star-like with long branches, while negative figures tend to be shorter, and round or fan-like. By
carefully pressing a piece of paper onto the dusted surface, he was able to
transfer these image onto the paper, demonstrating what was later to become
the process of Xerography. Drawings of positive and negative figures captured by Dr. Lichtenberg are shown below.
Positive Lichtenberg figure
Negative Lichtenberg figure
Later researchers included Gaston Planté (mid 1850's), Thomas Burton Kinraide (late 1800's), Dr. Carl Edward Magnusson, and Dr. Arthur Von Hippel
(1930's+). These researchers used photographic film to directly capture
the light emitted by positive or negative high voltage discharges along
dielectric surfaces. Von Hippel discovered that Lichtenberg figures were actually created through complex interactions between ionized gas (corona
or electrical discharges) and the dielectric surface below. It
was also found that increasing the applied voltage or reducing the
surrounding gas pressure caused the length of the figures to increase.
This
property was used in klydonographs, special recording instruments
that photographically
recorded the size and shape of Lichtenberg figures that appeared during abnormal electrical surges on power lines.Klydonographs allowed lightning researchers and power system designers to
estimate the peak voltage
and polarity
of abnormal transients caused when lightning struck power lines.
A schematic diagram of the main parts of a klydonograph is shown on the leftmost drawing below, along with
examples of "klydonograms" from equal magnitude positive and negative high voltage
transients.
Schematic view of a klydonograph showing the position of the
photographic film and HV electrode. Light from high voltage
discharges creates a permanent photographic record of the event.
From W.W. Lewis, "The Protection of Transmission Systems
Against Lightning", John Wiley & Sons, 1950
Lichtenberg
figures are now known to often occur during electrical breakdown processes
within most gases, insulating liquids, and solid dielectrics.
Lichtenberg figures can be created very quickly (tens of nanoseconds) when dielectrics are
heavily overstressed, or they can grow very slowly , through a series of low energy partial discharges, evolving into partially conductive surface patterns or 3D "electrical trees".
Electrical trees can form on contaminated insulator surfaces, within
dielectrics due to internal defects or voids, or at points where an
insulator has been physically damaged.
The first report of
Lichtenberg figures being created inside clear plastic by directly injecting
electrons was from physicists Arno Brasch and Fritz Lange in the late 1940's. Electrons
are tiny, negatively charged particles that orbit the nucleus of the atoms that make up all condensed matter. At
their laboratory at AEG (Berlin, Germany), they used a 2.4 million volt Marx Generator to
provide high energy pulses to drive an electron beam
accelerator. An
article about their research and the accelerator (which they called a
"Capacitron") appeared in the March 10, 1947 issue of LIFE Magazine.
The Capacitron could deliver pulsed electron beam currents of up to
100,000 amperes. The ionized air created by the exiting electrons resembled a bluish-violet rocket flame. A
complete set of previously unpublished pictures, including Lichtenberg figures inside a clear block of plastic, is now available online via Google.
Pioneering
research on the detailed
behavior of charge storage and movement within dielectrics was first performed by Dr.
Bernhard Gross in the early 1950's. Dr. Gross confirmed that internal Lichtenberg figures could be created
within a variety of polymers and glasses by injecting them with high energy electrons using a linear accelerator (LINAC). The techniques that we use to make our Lichtenberg figures build upon
the theoretical work and techniques developed by Gross, Brasch, and Lange. The resulting figures are sometimes called electrical
trees, electron trees, beam trees, or even spark trees. We call them Captured Lightning® sculptures.
How do we create our Captured Lightning® sculptures?
We have continued to develop and refine irradiation and material
processing techniques to create a truly unique line of 2D and 3D sculptures.
We start with specially cut and polished specimens of a clear polymer, polymethylmethacrylate (PMMA).
This material is commonly known as acrylic, or various trade names such as
Lucite, Plexiglas, or Perspex. PMMA has a unique combination of
optical clarity and superior electrical
and mechanical properties. Other clear polymers, such as polycarbonate
(PC),
polystyrene (PS) , polyethylene terephthalate (PET), and polyvinyl
chloride (PVC) will also work to varying degrees, but unfortunately most of
these materials form dark gray or blackish trees instead of the sparkling
mirror-like fractures seen within acrylic.
We
create our sculptures by injecting specimens with high velocity
electrons using high power particle accelerators. The energy of the accelerated electrons is measured in millions of electron Volts (or MeV). The
LINAC that we use accelerates electrons to a kinetic
energy
of between three and five MeV. At these energies, electrons leaving the accelerator are traveling at relativistic velocities - between 98.5% and
99.6% of the speed of light.
When a specimen is irradiated, the relativistic electrons are driven
deep inside. The penetration depth is determined by
the
initial energy of the electron beam, the material's dielectric properties, and its atomic density.
The higher the initial electron beam energy, the deeper the electrons will penetrate. As
the specimen is irradiated, huge numbers
of electrons accumulate inside the acrylic, creating a cloud-like
layer
of excess negative electrical charge called
a space charge.
Since acrylic is an excellent dielectric, the injected electrons cannot escape. They accumulate under continued irradiation, causing a cloud-like region of negative space charge to grow deep inside the specimen. By
carefully changing the orientation of the specimens and passing them
through the beam in two or more passes, or by rotating them as they are irradiated, complex 3-dimensional space
charge regions can be produced.
As the space charge grows, the resulting electrical field also
increases.
Eventually, the electrical stress from the increasing electrical field overcomes the
dielectric strength of the acrylic, and some of the chemical
bonds that hold the acrylic
molecules
together are ripped apart. This strips away additional free electrons (a process
called ionization). These newly-freed electrons are also accelerated by the
electric field, ionizing even more acrylic
molecules, and creating additional free electrons in a runaway process. Within billionths of a second, electrically
conductive channels form within the acrylic as the material undergoes dielectric breakdown.
Once breakdown occurs, the previously trapped charges suddenly rush out, accompanied by a
loud bang(!), and thousands of electrically conductive branches feed current into a main "lightning
bolt" that exits the acrylic with a brilliant flash. Although
pictures of the discharge seem to suggest that we are injecting high
voltage into the block, in reality we are removing the high voltage
that was previously trapped within the block. Dielectric breakdown
typically occurs within
an incredibly short amount of time. For example, the electrical discharge within a 2 inch square specimens may only last for only 20
billionths of a second! The following image shows a 4 inch square specimen as it was being discharged:
(Photo courtesy of Theodore Gray)
The
escaping lightning bolts leave behind permanent fingerprints in the acrylic,
forming a branching "lightning fossil" within. The high current
electrical
discharges may reach hundreds, or even thousands, of
amperes. The hot plasma within the discharge causes the acrylic to melt and fracture along each path, and higher
current "roots" may slightly char the acrylic.
The
exit point of the discharge appears as a small hole on the surface of
the acrylic. The
discharge point is typically located at a surface defect, or where a
point of
external mechanical stress
has
weakened the dielectric. The defect concentrates
the electric field, creating a weak link where the breakdown process
can begin. Although we inject a huge amount of negative charge into our
specimens, the electrical breakdown process actually originates from points which
are more electrically positive (versus the space charge), so our Captured Lightning® sculptures are
actually "positive" Lichtenberg figures!
Actual discharge current measurements... and a paradox
During
our 2007 production run, we were able to capture the shape of
the current waveform as we discharged a number of 4" x 4" x
3/4" specimens (similar to the specimen above). A special holding
fixture was constructed with copper foil plates that made physical contact with the large surfaces of the
charged acrylic
specimen. A heavily insulated wire connected the pair of foil
plates to the sharp tool which was used to discharge the specimen.
This
wire was also passed through the center of an Ion Physics 50 kA
wideband
current transformer
(CT). The current transformer transformed the discharge current pulse
that flowed through the wire
into a voltage pulse that could be captured and stored within a high speed
Tektronix digital
storage oscilloscope. The digitized waveform data was subsequently
analyzed using an Excel spreadsheet in order to
recreate the following waveform.
We
found that, for 4" x 4" specimens, the discharge
lasted for only 120 billionths of a second. For the
specimen shown below, the
peak current was almost 600 amperes, and was seen to consist of four
separate current peaks. Other specimens showed between three and seven
peaks. This suggests that the electrical trees apparently propagated via a series
of advancing waves. Each current peak reflects a surge of newly conducting
channels ("streamers" and "leaders") as they blasted their way into previously
untapped reservoirs of
charge within the acrylic, followed by a brief pause, then another
surge, etc. The average discharge velocity was between 8.5 x 105 and
1.3 x 106
meters/second (526 and 790 miles/second, or around 0.3% the speed of
light). However, pauses
between successive current surges suggest that the peak discharge
velocity during growth phases was significantly faster. Surprisingly,
the
average velocity within the specimen was actually 10-100 times faster
than the
velocity of positive lightning leaders in air. This is thought to be
due to the extremely high electrical field (estimated to be ~10-20
million volts/cm) at the tips of the propagating discharges within the
acrylic.
However, the high streamer velocity creates a paradox, since it is over 800 times the speed of
sound within
PMMA. This is inconsistent with Griffith's theory of crack propagation within solids,
which
predicts that the maximum crack propagation speed within a solid
is limited to the Rayleigh speed (i.e., the speed of sound) or 1.614
km/second for PMMA. The
current waveform clearly demonstrates that the chains of cracks
and gas
channels developed at a speed that was almost three orders of magnitude
faster than it should be from classical materials theory. We
suspect that that potential energy
(from the intense internal electrical field) is causing "electronic
breakdown" of the PMMA, generating a "detonation wave" of microcracks that
propagates through the charge layer at hypersonic speed. This is
an area ripe for future research. The discharge process
also generates a powerful shockwave (a loud BANG), and a brilliant,
miniature, blue-white "lightning" flash.
After
the main discharge, there are often hundreds of smaller
secondary electrical
discharges as small pockets of stranded charge redistribute
themselves
within the specimen. Larger figures often sparkle and sizzle for
tens of seconds
afterwards, making a sound similar to frying bacon, and intermittent
sparking has been observed up to 30 minutes later. These smaller
discharges often sting our fingers when partially discharged
specimens are handled. Click on the
following image to see some high resolution video taken during our
November, 2007 production run showing primary and secondary
discharges.
(Photo and video courtesy of Mike Walker and Theodore Gray) Click on the Above image to see a video clip
of many Lichtenberg figures being discharged
Video clip of a huge 18" Lichtenberg figure being created:
Following
is
another video clip of an 18" x 18" x 1" specimen being discharged during our 2005
production
run. Before discharging, the estimated potential of the internal charge plane was 2.2
million volts. Because of it's size, this specimen had
considerably more
stored electrostatic energy, and the discharge was quite loud and very
bright! The actual discharge, although very brief, saturated the
video camera image sensor. A multitude of secondary discharges can also be observed after
the main discharge. (Video courtesy of Terry Blake. Specimen
was owned, and discharged, by Jeff Larson.)
The
rounded, crystalline flakes
that make up the Lichtenberg Figure are actually chains of tiny conchoidal
fractures. These
shell-shaped
fractures are characteristic of the way noncrystalline
(amorphous)
materials fracture when stressed beyond their breaking point. Since
these tiny fractures reflect light like tiny mirrors, illuminating the
figures through the edges causes the entire figure to glow brilliantly
with the reflected color(s) of the external light source.
Lichtenberg figures are fractals
Lichtenberg figures exhibit branching patterns which
tend
to look similar at various scales of magnification. This self-similar property suggests that Lichtenberg figures can be modeled
using a branch of mathematics called Fractal Geometry. Self similarity is a key property of fractals.
Our Lichtenberg Figures show a range of fractal patterns depending upon
the magnitude of charge injected into the acrylic and how and when the
specimens is discharged. Branching figures are technically called
"dendritic" or "arborescent" (tree-like). If a large amount
of electrical charge is injected into the specimens and it is then
immediately discharged, a very dense dendritic discharge is
created, such as the leftmost figure below.
These dense discharges are quite similar in appearance to ferns or moss
agate. If the level of charge is reduced and the specimen manually
discharged, a more classical, lightning-like or tree-like discharge
results as the
center example below. If premature breakdown occurs as we are
actively irradiating a specimen, tangled "chaotic" discharges occur.
Some specimens show combinations of these basic patterns.
Chaotic Discharges
(prematurely discharged
while being irradiated)
Self
similarity can easily be seen in the following sequence of zooms
from a 12" x 12" Lichtenberg Figure with nominal dendritic discharges.
The branches become finer and
hairlike, ultimately disappearing. Similar fractal patterns are seen in
aerial views of some rivers and their tributaries, branching tree
limbs, and the arteries, veins, and capillaries within your body.
It has recently been discovered that Lichtenberg figures can be modeled using a process called "Diffusion Limited Aggregation" or DLA. A useful macroscopic model that combines an electric field with DLA is called the Dielectric Breakdown Model or DBM.
The dielectric breakdown model appears to describe the branching growth that
characterize the dielectric breakdown process within solids, liquids, and gases.
Solarization, fluorescence, and birefringence: During
irradiation, the acrylic glows a brilliant blue-white
color. Although radiation chemistry studies suggest that this may be a combination of luminescence or Cherenkov radiation, the reason(s) are not fully understood. You may also notice that our specimens have a
discharge-free zone along all of the outside edges. This is because PMMA
is not a perfect insulator, so some of
the internal charge "leaks away" to the outside surfaces. This reduces the amount of stored charge along the
perimeter to the point where the electrical field is no longer sufficient to break down the
acrylic.
You may also notice that a portion of the acrylic has
an amber tint - this is called solarization.
Solarization is
thought to be caused by the formation of structural changes and defects through electron
collisions, high energy x-rays, and the temporary trapping of ionic charges
within the molecular structure of
the PMMA. Solarization usually occurs only within the region between the surface that was
irradiated by the electron beam and the discharge layer. During irradiation, electrons are initially traveling at
about 99% of the speed of light. As they penetrate the specimen, they collide with acrylic molecules, rapidly coming to a stop within a fraction
of an inch. The electrons in the beam have a tremendous
amount of kinetic
energy, and as they suddenly brake to a stop,
they release this energy in the form of heat and very powerful X-rays.
As the acrylic absorbs electrons and x-rays, various physical and
chemical reactions occur that may alter its physical and optical
properties. Although
the specific causes of solarization are not fully understood, there
is evidence that irradiation creates unstable, or longer-lived
"metastable", compounds that preferentially absorb light at the blue end of
the spectrum (250 - 400 nm). This causes some or all of the clear PMMA to turn green, brown, or amber.Some electrons may become trapped for months,
perhaps years, afterwards, creating color centers which also contribute to the solarization.
Many
irradiated specimens initially turn a bright lime green color which,
over a period of minutes to hours, fades to amber. The colored region may
take months, or even years, to fade away.
Fading can be accelerated by gently heating the block in the
presence of oxygen, or by leaving the specimen in sunlight for an
extended period of time. As oxygen diffuses into the PMMA from the
outside and the discharge layer, it bleaches the solarized region,
causing it to gradually become thinner and thinner, eventually
disappearing altogether. Most
older Lichtenberg figures become completely bleached. Although they no
longer show any solarization, some specimens may show slight residual
"fogging" from irradiation damage. Some specimens exhibit little
initial
solarization, while a small number of specimens appear to permanently
retain
their amber color. Curiously, it has been found that fully charged
specimens will retain their green color for many days when kept at dry
ice temperatures. These specimens then change to amber after being
discharged. There are clearly several different processes that are
associated with solarization.
Recently, it has also been discovered that the solarization layer may sometimes be fluorescent.
An amateur scientist from New Zealand, Daniel Rutter, discovered that monochromatic light from a green laser pointer changes color
when passed through the solarized layer of a Lichtenberg figure. More
recently, we discovered that the light from a near-ultraviolet
source (such as a Blu-ray laser or even bright blue LED's) sometimes
causes the solarized region to glow with a brilliant yellow-green
fluorescence. This occurs on some specimens but not others, and as the
solarization fades over time, so does the mysterious fluorescence.
Most specimens also exhibit
slight changes in refractive index near the Lichtenberg discharge region. These
behavioral differences are
thought to be due to variations in the acrylic blends used
by various manufacturers, permanent irradiation-induced changes to the
polymeric structure of the acrylic, and residual mechanical stresses near the discharge fractures. Residual
stresses near the Lichtenberg figures can easily be seen as multicolored regions
near the discharge plane when a sculpture is illuminated by polarized
light and then viewed through a second polarizing filter. When physically stressed, PMMA exhibits a property called birefringence.
When viewed through polarizing filters, stress-induced
birefringence causes changes in color that are related to the amount
and distribution of otherwise hidden stresses within the PMMA.
Natural Lichtenberg figures - fulgurites and lightning discharges
Occasionally, nature also creates "fossilized lightning". Called fulgurites,
these
are hollow and sometimes branching tubes that are formed when the powerful
electrical
current from a lightning strike creates underground discharge channels within poorly conducting sandy or sandy-clay soils. These hollow channels were formed as the intensely hot channel from the lightning arc fused surrounding sand
and soil particles which then cooled to form a solid glassy tube. Some
fulgurites also exhibit fractal characteristics as they split into
smaller diameter root-like branches at further distances from the site
of the main strike.
Lichtenberg figures, sometimes called "lightning flowers" or "skin feathering",
are sometimes formed
beneath the skin of unfortunate humans who have been struck by lightning. The victim will often have one
or more reddish radiating feathery patterns that branch outward from
the entry
and
exit points of the strike:
(From "Lichtenberg Figures Due to a Lightning Strike" by Yves Domart, MD, and Emmanuel Garet, MD,
New England Journal of Medicine, Volume 343:1536, November 23, 2000
Medical
terms for this phenomenon include arborescent lightning burn,
arborescent erythema, keraunographic markings or simply ferning
patterns. Although the exact causes are subject to
some debate,
they appear to be the result
of damage to small capillaries under the skin, perhaps caused by the
flow of electrical current
from the stroke, or by shock wave bruising from external flashovers
just
above
the skin. The arborescent (tree-like)
reddish marks fade away over a
period of
hours
or days. They are recognized by forensic pathologists as clear evidence
that a victim has been struck by lightning. The patient above survived
with no permanent injuries, and the lightning flowers completely faded
within two days. A small Lichtenberg figure
has
also been observed at the point
where a high voltage spark penetrated the skin of an unfortunate (but
surviving) local electrical experimenter who took an accidental "hit"
from a
homemade 60,000 volt Marx Generator.
A similar phenomenon is sometimes seen when
lightning
hits a grassy field, as in this picture where lightning struck a
flagpole, leaving this beautiful 25 foot Lichtenberg figure on the
green of a golf course:
(From "Lightning and Lichtenberg Figures" by Cherington, Olson and Yarnell, Injury, Volume 34, Issue 5, May 2003)
Note how similar the above figure appears to the Lichtenberg figure within this specimen (lit from below by blue LED's):
High voltage discharges to the surface of water can also create Lichtenberg figures. Some very beautiful examples
of
both positive and negative Lichtenberg figures on water surfaces can be seen on Dr. Colin
Pounder's Lichtenberg figures web site.
Natural lightning sometimes creates transient "Lichtenberg Figures" in the sky. Air is an excellent dielectric and, although the physical breakdown
mechanisms
for air and PMMA are considerably different, the appearance of the
branching
discharges is quite similar. So it should not be surprising
that the
branching forms of natural lightning also have fractal
characteristics. This similarity can clearly be observed during "anvil crawler" and horizontal "spider lightning".
Spider lightning follows a positively charged cloud layer, and the
slowly propagating discharges can crawl across the sky for 30-40 miles
- literally spanning from horizon to horizon. On a much smaller scale, transient Lichtenberg figures
(often mistakenly called St. Elmo's Fire) often appear on the outer
surface of cockpit windows of airplanes when they fly near or within thunderstorms.
Similar
branching fractal patterns also occur when thunderstorms generate electrically conductive leaders that
propagate downward from a charged cloud to the ground below. When one
of these leaders connects with an unfortunate object on the ground, a high current surge (called the return stroke)
rushes back upward through the completed path, resulting in Cloud-to-Ground (CG) lightning
strike.
Exceptional examples of downward propagating positive leaders have been captured by South Dakota lightning
researcher, Tom Warner. Using high speed video imaging equipment, he
was able to capture the downward progression of leaders and the return
stroke from a positive lightning bolt. Positive lightning
is a significantly rarer (and considerably more dangerous!) form of lightning than negative lightning. The
"slow motion" video (below) shows the air breaking down, forming
glowing conductive plasma paths (called leaders) that fan
downward from a huge reserve of positive charge within the cloud
above. The brightly glowing tips of the positive leaders smoothly propagate,
unlike
negative leaders
which propagate in a series of discrete jumps (called stepped leaders). The
first descending leader to finally connect with the Earth below
completes the circuit, resulting in a powerful
Positive Cloud-to-Ground (+CG) lightning discharge.
The video clip
below was captured at 7200 frames/second (FPS), and the actual elapsed
time for the clip was only a little longer than three
thousandths of a
second. The speed of the propagating leaders was between
3 x 104 and 6.5 x 105 meters/second. This clip even contains a single frame
which captures the beginning of the return stroke from the Earth going
back up one of the leader channels. Even at the majestic scale
of natural lightning, you can clearly see similarities between the
collection of branching leaders and Lichtenberg Figures.
Positive lightning also has a very long lasting "tail" of
follow-through current which typically lasts for several hundred
milliseconds after the initial strike
connects to ground. The combination of long propagation distance (often
many miles from the main storm), very high current (up to 300,000
amperes), and long follow-through current make positive lightning
exceptionally dangerous. It tends to set fire or kill anything, or
anyone, unfortunate enough to be in its path. More of Tom Warner's
fascinating videos can be seen on his page on YouTube.
Lichtenberg Figures can also be seen at some high energy pulsed
power facilities, where deionized water is sometimes used as a dielectric to briefly store
large amounts of electrical energy. The famous photo below is from Sandia National Laboratory's
mighty Z
Machine, the world's largest pulse generator. After
the completion of a high energy experiment, the water breaks down from the huge electrical stress,
becoming an electrical conductor that safely dissipates unwanted
residual
energy from the system. The filamentary breakdown paths form Lichtenberg figures that dance across
the water's surface. If you look closely, you'll notice that
many of the radial paths actually trace out high voltage
electrical field lines along the surface of the water. Although
impressive, this display is only dissipating "left over" energy,
representing only a very small fraction (perhaps 5%) of the energy that was
actually used during the previous pulsed power experiment.
(Click for a higher resolution 840 x 554 pixel image, 561 kB)
Holding a Lichtenberg Figure is about the closest
you can
come to holding fossilized lightning in your hand - Captured Lightning® is indeed an accurate description. Most
of the Lichtenberg figures shown on our web site were produced
by
irradiating various acrylic shapes using a 5 MeV Continuous Wave (CW)
research LINAC - a 150 kW high power electron beam accelerator called a Dynamitron. A few were created using pulsed linear accelerators at significantly higher beam energies (10
- 15 MeV). Lichtenberg figures are completely
safe - they have been electrically discharged and have no residual radioactivity or X-radiation.
And, as with snowflakes, every Lichtenberg Figure is a one-of-a kind treasure.
Following
are a pair 3-D images that can be rotated 360 degrees so that you can fully
enjoy the beauty of our doubly-irradiated Lichtenberg figures. The irradiation process
results in very complex discharges within and
between the two charge layers. Please wait for the images to
completely
download, then drag your mouse to rotate the images for a full 360
degree view. (Warning: you'll need a high speed Internet connection to view these since
they are each ~6 MB files and will take quite some time to fully load.)
3D Rotatable Image
3D Rotatable Image
"Heavy Weather"
(Courtesy of Theodore Gray)
"Windblown Lightning"
(Courtesy of Theodore Gray)
Very
few people have actually seen
or held one of these rare objects, and far fewer have had the opportunity to own one.
Stoneridge Engineering is proud to be the world's most experienced provider for these beautiful and rare
treasures. We
offer a wide selection of 2D and 3D figures ranging in size from
affordable 2 inch specimens through museum quality figures
as large as 24 inches by 36 inches. Please visit our galleries to see the world's most beautiful Lichtenberg figures:
Everyone is a genius at least once a year.
The real geniuses simply have their bright ideas closer together.
– G.C. Lichtenberg
References and Further Reading: 1. Gross, Bernard, "Irradiation Effects in Plexiglas", Journal of Polymer Science, Volume 27, 1958, Issue 115, Pages 135 - 143 2.
Hashishes. Yuzo, "Two Hundred Years of Lichtenberg Figures", Journal of
Electrostatics, Volume 6, Issue 1 , February 1979, Pages 1-13
3. Chadwick, K. H., "The Effect of Light Exposure on the Optical
Density of Irradiated Clear Polymethylmethacrylate", 1972 Phys. Med.
Biol. 17, Pages 88-93 4.
Chadwick, K. H., and Leenhouts, H. P., "Fading of
radiation-induced optical density in polymethylmethacrylate on oxygen
diffusion", Phys. Med. Biol. 15 No 4 (October 1970), Pages 743-744
5. L. Niemeyer, L. Pietronero*, and H. J. Wiesmann, "Fractal Dimension
of Dielectric Breakdown", Phys. Rev. Lett. 52, 1033–1036 (1984) 6.
Gardner, Donald G., et. al., "Radiation-induced changes in the index of
refraction, density, and dielectric constant of poly(methyl
methacrylate)", Journal of Applied Polymer Science, Volume 11, Issue 7,
July 1967, Pages 1065-1078 7.
Akishin, A.A.; Tseplyaev, L.I., "Edge effect in radiation-charge
dielectric materials", Physics and Chemistry of Materials Treatment, v
31, n 1, Jan.-Feb. 1997, p 30-1. A similar paper is also contained
within the book "Effects of Space Conditions on Materials", Akishin, A.
I., Nova Science Publishers, 2001, ISBN 1590330285
8. Fothergill, J.C.; Dissado, L.A.; Sweeney, P.J.J., "A
discharge-avalanche theory for the propagation of electrical trees. A
physical basis for their voltage dependence", Dielectrics and
Electrical Insulation, IEEE Transactions on, Volume 1, Issue 3 , June
1994, Pages 474 - 486
9. R. A. Galloway, T. F. Lisanti and M. R. Cleland, "A new 5 MeV –300
kW Dynamitron for radiation processing", Radiation Physics and
Chemistry, Volume 71, Issues 1-2, September-October 2004, Pages 551-553
10. Sessler, G.M.. "Charge distribution and transport in polymers",
Dielectrics and Electrical Insulation, IEEE Transactions on, Volume 4 ,
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