Plasma Coupling Using COMSOL Results¶

In this example, we use a COMSOL front-face coupling calculation provided by ORNL, exported as a standard Touchstone file.

The Touchstone file is first import as a scikit-rf Network, which is then modified to fit the WEST ICRH antenna electrical model requirements.

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import numpy as np
import skrf as rf

# WEST ICRH Antenna package
import sys; sys.path.append('..')
from west_ic_antenna import WestIcrhAntenna

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front_face_conventional = rf.Network(
    '../west_ic_antenna/data/Sparameters/front_faces/COMSOL/ORNL_front_face_conventional.s4p')
print(front_face_conventional)  # 50 Ohm S-param component at a single frequency of 55 MHz

The ports have been defined as:

So before to use the S-parameters directly to feed the electrical model, we need to:

deembed the ports by 0.3m.
renomalize port reference impedance to the front-face coax characteristic impedances.
reverse ports 2 and 3.

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# creating a 50 Ohm dummy coax line to be removed from the front face 
media_coax = rf.DefinedGammaZ0(frequency=front_face_conventional.frequency) # 50 Ohm TEM media
extra_line = media_coax.line(d=0.3, unit='m')
# deembedding all the 4 pourts
for port_idx in range(4):
    front_face_conventional = rf.connect(front_face_conventional, port_idx, extra_line.inv, 0)

We expect the port to have a characteristic impedance of about 46.64 ohm, so we renormalize the Network to fit this need:

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front_face_conventional.renormalize(46.64)  # done inplace

And finally, for historical reasons (may change in a near future ;), the S-matrix port ordering should be ajusted:

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front_face_conventional.renumber([1, 2], [2, 1]) # done inplace

OK, so now we can create the WEST antenna object:

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ant = WestIcrhAntenna(front_face=front_face_conventional,
                     frequency=front_face_conventional.frequency) # restrict to single frequ

Let's match the antenna for this coupling:

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Cs = ant.match_both_sides(f_match=55e6)

The coupling resistance of the antenna for this coupling in a nominal dipole excitation is:

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power = [1, 1]
phase = [0, np.pi]

# Coupling resistance
ant.Rc(power, phase)

The voltage and currents are:

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power = [1.6/2, 1.6/2]  # MW, to adjust to fit with experiment
phase = [0, np.pi]  # rad

abs(ant.voltages(power, phase))  # results in kV

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abs(ant.currents(power, phase))  # results in kA

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