TITLE: Tokomak Fusion Reactor
NAME: Aaron Gage
COUNTRY: USA
EMAIL: agage@mines.edu
WEBPAGE: http://www.mines.edu/students/a/agage
TOPIC: Great Engineering Achievements
COPYRIGHT: I SUBMIT TO THE STANDARD RAYTRACING COMPETITION COPYRIGHT.
JPGFILE: amgtorus.jpg
ZIPFILE: amgtorus.zip
RENDERER USED: 
    POVray 3.0 for Linux

TOOLS USED: 

        Concept:   xv to enlarge photos of real reactor
        Modelling: NONE

RENDER TIME: 
    8D 9H 57M CPU time over 209 06 49 real time

HARDWARE USED: 
    i486DX2/66 with 32 Megs RAM under Linux 2.0.28

IMAGE DESCRIPTION: 


        The modern fusion reactor uses powerful magnetic fields to contain a
plasma mixture of Deuterium, Tritium, and Lithium within a toroidal band.
Here we see a tokomak reactor running, as it pushes the boundaries of
sustainable fusion reactions.


DESCRIPTION OF HOW THIS IMAGE WAS CREATED: 


        This image has been a fairly concentrated effort over six weeks to
model and texture a tokomak fusion reactor.  I think it's been worth the
effort.  So, starting at the beginning, here is how this image was made.

        I first got the inspiration to do a fusion reactor after drawing a
total blank on other ideas.  To me, a great engineering achievement must have
certain characteristics.  It must be something that should not have been
possible given the technology available when it was built.  It should defy, or
define, the boundary between what is possible and what is not.  And it should
be a lasting achievement, which will influence or create history.  Finally,
it should be nice to look at, since this is a raytracing competition.

        To satisfy these constraints, a bridge or tower is not enough.  I
considered pocket watches, since they are ornate and intricate, but better ones
have been done than I could do.  Anything else would require a lot of outdoor
or space background, which I've done too much of lately.  So I decided on
the tokomak.

        The scene modelled in this image is based on three photographs taken
of the Joint European Torus (JET) tokomak.  After gaining permission to use the
images and idea, I used xv to magnify certain regions and extract approximate
dimensions.  More about fusion reactors in general and the JET project will
appear at the end of this file.

        The scene was made up of 7534 separate objects, at least by POVray's
count.  This really amounts to about 45 separate components (rings, plates,
paneling) that were created and placed by hand.  All of the primitives used
were fairly basic: boxes, cylinders, spheres, torii, planes, superellipsoids,
and cones, with a healthy amount of CSG and lots of #while statements.  While
it isn't very readable, and in itself is not enough to recreate the scene, the
supplied archive ought to have the .inc file I built, which has all of the
items in it in their primitive form.  I'll spare the bandwidth of describing
everything, but a few things need mentioning.

        A difficult trick was getting rings of plates arranged without having
them overlap.  The biggest example of this is the top of the torus, where there
is an umbrella of reflective plates that are all kept separate.  For this I
subtracted out planes at just enough of an angle to do the job as I swept
a single arc of those plates around the Y axis.  The same basic thing took
place at the bottom, where there is a circular wall (with a groove down the
middle and ramps on either side); I just used planes to cut out the parts that
should have been overlapping.  This allowed me to make both ends of the
individual blocks stay the same distance from their neighbors.

        All of the rings in the scene are differences of cylinders or cones,
depending on the curvature needed.  All of the pipes are torii and cylinders
which are meant to poke into the shadows; mostly just to draw the eye.  The
bolts were cylinders squared off by subtracting off planes, and adding a
sphere to the top.  And the band of plasma was just a torus with a halo.

        The only area that I think could have used some work was my texturing.
For the dead areas between the various banks of tubes, I wrapped the entire
torus in a loosely-fitting shell of conic rings and finally a sphere to capture
all light within the scene.  In order to keep the depth from being obvious, I
lit this background region with ambient light only, turning off the diffuse
light, so no shadows would fall on the metal (to cause an illusion about
the true depth).  I wanted to capture the idea that there were just more
miscellaneous bits of metal back there, odd pipes and plates that were too
fine to model directly.  I'm not sure if this effect has worked to my
satisfaction.  Focal blur onto the middle of the torus might have helped
that effect, by adding a certain vagueness to the background.

        I also would have liked using a camera angle of less than 90 degrees.
However, anything less would not have allowed so much detail to be seen in
one image (since this model begs to be animated).  As it is, there are some
details that are only visible through reflection.

        Now for a little information about fusion reactors.

        Fusion works, but not well enough to be applied to power generation
(yet).  As far as I know, at the time of this writing, the best performance
a fusion reactor can provide is to return 650f the energy put into it.
Not bad, really.  As soon as it passes 100%, we have a relatively cheap,
safe, and clean energy source for the future of mankind.

        The tokomak reactor works by squeezing plasma (metals and gasses at
extremely high temperatures) into such close confinement that they fuse into
different compounds.  This fusion releases a tremendous amount of energy,
which can be captured.  In order to generate an environment that can contain
plasma, a coil of powerful magnets generates a toroidal field within the
reactor that suspends the plasma totally above all surfaces in the torus.
These constricting magnetic fields also squeeze the plasma together, which
helps the fusion process along.

        The inspiration for this image came from the JET web page, which can
be found at http://www.jet.uk including news releases about current fusion
performance, a tour of the reactor (including the images I modelled my scene
after), and other interesting resources.  Since the contents of those pages
are intellectual property of the JET project, I obtained permission before
using their images to create a likeness of their reactor.

        This image has certainly been the most detailed that I've done,
and I will hesitate before doing anything this time consuming again.  But
as I said before, the final result was well worth the work.