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```									Some More Quick Advice on
The Computer Project
Chris Clark
cclark3@wisc.edu
•Consider the provided files a starting point
•You will need to write a fair bit of your own
•If using Matlab outside of COE need to authorize the
tethered software at: https://tethered.cae.wisc.edu/authorize/
•Remove diagnostic plots from field_line_follow();
•Modify field_line_follow to take an arbitrary integration
interval
•Modify field_line_follow to also integrate the total length
•Modify field_line_follow to also integrate 1/B dl
•Create a second version of field_derivates /
field_line_follow to have error field and islands
Some Pseudo-Code
(Flux Surface Ploting)
for each starting R         %Arbitrary points across r
Z=Phi = 0             %Arbitrarily start at midplane
for (# of transits to map)
follow field line (2 pi)   %Can do 2 pi / 7
plot R,Z
end for;
end for
Algorithm for Finding the Axis
Pick an R,Z that looks near the axis, but that are definitely
outboard of it
While(haven’t found axis) %Arbitrary points across r
follow field line (largish # of rotations)
if (all points very close to starting point)
found axis
else
move next starting point inboard
Algorithm for iota Profile
For (Each Flux Surface)
# Poloidal Transits = 0;
For (100s of transits)
for (#subtransits >> 1/iota)
If (crossed midplane)
PoloidalTransits++
end for;
End for;
End for;
Iota = PoloidalTransits / ToroidalTransits;
Algorithm for Mod B
1) Follow a field line a couple of times around the machine
2) For each point in the trajectory, calculate the strength of
B using the biot-savart code
Toroidal Flux
1) Find the flux surface with many points
2) Make a grid of points that covers the entire flux surface
and then some
1) Matlab has min and max functions to help do this
3) Test each grid cell for being in or out of the flux surface
1) Inpolygon() is one way to do this
4) Assume that the grid is small enough such that it has
one value of B
Integrating 1/B dl
• You know how to integrate with respect
to phi
• Transform problem to be in those terms