Magnetic Fields and Magnetic Diagnostics for Tokamak Plasmas

Magnetic fields and tokamak plasmas
Alan Wootton
Table 2. Correction coefficients α s and α f
for B θ sensors.
outside (r c
≥ r s
)
α s
α f
inside (r s
≥ r c
)
α s
α f
correction
factor
πr s
2r c
,≥ 0
− πr c
2r f
≤ 0
− πr s
2r c
,≤ 0
− πr c
2r f
≤ 0,
For comparison, table 2 shows the coefficients α s and α f for the multipole moment coil system
[1], with coils either inside or outside the vessel. Note that the multipole moment sensing coils
are only sensitive to currents inside the contour on which they are wound, and thus α f = 0.
Table 3. Correction coefficients α s and α f
for multipole moment sensors.
outside (r c
≥ r s
)
correction
factor
α s
α f
0
inside (r s
≥ r c
)
α s
0
α f
0
πr s
2r c
,≥ 0
Numerical values applicable to TEXT are given in table 4, for r c = 30 cm (inside) or 34 cm
(outside), r s = 32 cm, r f = 50 cm. We see that, as far as pickup from the shell currents (α s ) is
concerned, the B θ coils outside the vessel are no worse than the moment coils.
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