Grating Polarizers at 170 GHz for ECRH Systems: Low Power Tests and Simulations

Hannah M. Hoffmann; Sudheer K. Jawla; Michael A. Shapiro; Gregory Hanson; Richard J. Temkin

doi:10.1109/TAP.2018.2851377

Grating Polarizers at 170 GHz for ECRH Systems: Low Power Tests and Simulations

Hannah M. Hoffmann
, Sudheer K. Jawla
, Michael A. Shapiro
, Gregory Hanson
, Richard J. Temkin

Research output: Contribution to journal › Article › peer-review

2 Scopus citations

Abstract

The elliptical polarization produced by a pair of sinusoidally profiled miter-bend grating polarizers has been measured experimentally and found to be in excellent agreement with theory. The polarizers were designed to be used at 170 GHz in the miter bends of a 63.5 mm corrugated metallic waveguide for creating the arbitrary elliptically polarized microwave beam needed for electron cyclotron resonance heating of plasma. Using a vector network analyzer to generate a linearly polarized HE₁₁ incident mode, each polarizer was individually tested to measure the rotation α and ellipticity β of the elliptically polarized reflected microwave beam as a function of the grating rotation angle. The grating polarizers were then tested together to measure the elliptical polarization as a function of the angles of the combination of the two polarizers arranged sequentially on the transmission line. The map of the ellipticity versus grating angles agreed very well with numerical simulations using high-frequency structure simulator. Numerical simulations show that up to eight combinations of rotation angles of the two grating polarizers can provide the same ellipticity but with the varying ohmic loss, thus allowing the choice of settings to minimize the ohmic loss, a necessary consideration to minimize heating effects in megawatt power level systems.

Original language	English
Article number	8399867
Pages (from-to)	4719-4728
Number of pages	10
Journal	IEEE Transactions on Antennas and Propagation
Volume	66
Issue number	9
DOIs	https://doi.org/10.1109/TAP.2018.2851377
State	Published - Sep 2018

Funding

U.S. Department of Energy Office of Fusion Energy Sciences under Grant DE-FC02-93ER54186 Manuscript received March 6, 2018; revised May 23, 2018; accepted June 11, 2018. Date of publication June 28, 2018; date of current version August 31, 2018. This work was supported in part by the U.S. Department of Energy Office of Fusion Energy Sciences under Grant DE-FC02-93ER54186 and in part by the U.S. Department of Energy, UT-Battelle, LLC under Contract DE-AC05-00OR22725. (Corresponding author: Sudheer K. Jawla.) H. M. Hoffmann, S. K. Jawla, M. A. Shapiro, and R. J. Temkin are with the Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 USA (e-mail: [email protected]; [email protected]; [email protected]; [email protected]).

Keywords

Corrugated waveguides
Gaussian beams
gratings
microwave measurements
phase measurements
polarization

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10.1109/TAP.2018.2851377

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title = "Grating Polarizers at 170 GHz for ECRH Systems: Low Power Tests and Simulations",

abstract = "The elliptical polarization produced by a pair of sinusoidally profiled miter-bend grating polarizers has been measured experimentally and found to be in excellent agreement with theory. The polarizers were designed to be used at 170 GHz in the miter bends of a 63.5 mm corrugated metallic waveguide for creating the arbitrary elliptically polarized microwave beam needed for electron cyclotron resonance heating of plasma. Using a vector network analyzer to generate a linearly polarized HE11 incident mode, each polarizer was individually tested to measure the rotation α and ellipticity β of the elliptically polarized reflected microwave beam as a function of the grating rotation angle. The grating polarizers were then tested together to measure the elliptical polarization as a function of the angles of the combination of the two polarizers arranged sequentially on the transmission line. The map of the ellipticity versus grating angles agreed very well with numerical simulations using high-frequency structure simulator. Numerical simulations show that up to eight combinations of rotation angles of the two grating polarizers can provide the same ellipticity but with the varying ohmic loss, thus allowing the choice of settings to minimize the ohmic loss, a necessary consideration to minimize heating effects in megawatt power level systems.",

keywords = "Corrugated waveguides, Gaussian beams, gratings, microwave measurements, phase measurements, polarization",

author = "Hoffmann, \{Hannah M.\} and Jawla, \{Sudheer K.\} and Shapiro, \{Michael A.\} and Gregory Hanson and Temkin, \{Richard J.\}",

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AU - Temkin, Richard J.

PY - 2018/9

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N2 - The elliptical polarization produced by a pair of sinusoidally profiled miter-bend grating polarizers has been measured experimentally and found to be in excellent agreement with theory. The polarizers were designed to be used at 170 GHz in the miter bends of a 63.5 mm corrugated metallic waveguide for creating the arbitrary elliptically polarized microwave beam needed for electron cyclotron resonance heating of plasma. Using a vector network analyzer to generate a linearly polarized HE11 incident mode, each polarizer was individually tested to measure the rotation α and ellipticity β of the elliptically polarized reflected microwave beam as a function of the grating rotation angle. The grating polarizers were then tested together to measure the elliptical polarization as a function of the angles of the combination of the two polarizers arranged sequentially on the transmission line. The map of the ellipticity versus grating angles agreed very well with numerical simulations using high-frequency structure simulator. Numerical simulations show that up to eight combinations of rotation angles of the two grating polarizers can provide the same ellipticity but with the varying ohmic loss, thus allowing the choice of settings to minimize the ohmic loss, a necessary consideration to minimize heating effects in megawatt power level systems.

AB - The elliptical polarization produced by a pair of sinusoidally profiled miter-bend grating polarizers has been measured experimentally and found to be in excellent agreement with theory. The polarizers were designed to be used at 170 GHz in the miter bends of a 63.5 mm corrugated metallic waveguide for creating the arbitrary elliptically polarized microwave beam needed for electron cyclotron resonance heating of plasma. Using a vector network analyzer to generate a linearly polarized HE11 incident mode, each polarizer was individually tested to measure the rotation α and ellipticity β of the elliptically polarized reflected microwave beam as a function of the grating rotation angle. The grating polarizers were then tested together to measure the elliptical polarization as a function of the angles of the combination of the two polarizers arranged sequentially on the transmission line. The map of the ellipticity versus grating angles agreed very well with numerical simulations using high-frequency structure simulator. Numerical simulations show that up to eight combinations of rotation angles of the two grating polarizers can provide the same ellipticity but with the varying ohmic loss, thus allowing the choice of settings to minimize the ohmic loss, a necessary consideration to minimize heating effects in megawatt power level systems.

KW - Corrugated waveguides

KW - Gaussian beams

KW - gratings

KW - microwave measurements

KW - phase measurements

KW - polarization

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JO - IEEE Transactions on Antennas and Propagation

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M1 - 8399867

ER -

Grating Polarizers at 170 GHz for ECRH Systems: Low Power Tests and Simulations

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