Short wavelength far infrared laser polarimeter with silicon photoelastic modulators

Akiyama, T.; Kawahata, K.; Tanaka, K.; Okajima, S.; Nakayama, Keiichi I.

doi:10.1063/1.2957936

Cited by 5 publications

(1 citation statement)

References 27 publications

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“…In the Faraday rotation detection part, one wavelength is selected by using a Fabry-Perot interferometer (Filter), and its polarization rotation is detected with a dual photo-elastic modulators (PEMs) [7] made of highly resistive silicon. We already confirmed [8] good linearity between actual and evaluated polarization angle with an angular resolution of 0.01 degrees and a temporal resolution of 1 ms, which satisfy requirements from ITER diagnostics.…”

Section: Introductionsupporting

confidence: 72%

Progress in development of two color laser diagnostics for the ITER poloidal polarimeter

Kawahata¹,

Akiyama²,

Tanaka³

et al. 2012

J. Inst.

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Two color laser diagnostics using THz laser sources are under development for a high performance operation of the Large Helical Device and for future fusion devices such as ITER. So far, we have achieved high power laser oscillation lines simultaneously oscillating at 57.2 µm (1.6 W) and 47.7 µm (0.8 W) by using a twin optically-pumped CH 3 OD laser. And, we confirmed the usefulness of this two color laser operation for two-color laser interferometry in a test stand. For the measurement of the Faraday rotation angle we have developed a photo-elastic modulator (PEM) operating around 50 µm, and performed bench tests of the polarimeter with dual PEMs and demonstrated the feasibility of the polarimeter. The achieved angular resolution is 0.01 degrees with a time resolution of 1 ms, which satisfies diagnostic requirements for q-profile measurements on ITER (0.05 deg. at 10 ms time resolution). In this symposium, recent hardware developments and simultaneous measurements of a phase shift and a rotation angle will be presented.

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Section: Introductionsupporting

confidence: 72%

Progress in development of two color laser diagnostics for the ITER poloidal polarimeter

Kawahata¹,

Akiyama²,

Tanaka³

et al. 2012

J. Inst.

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Design of a dispersion interferometer combined with a polarimeter to increase the electron density measurement reliability on ITER

Akiyama

Sirinelli

Watts

et al. 2016

Review of Scientific Instruments

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A dispersion interferometer is a reliable density measurement system and is being designed as a complementary density diagnostic on ITER. The dispersion interferometer is inherently insensitive to mechanical vibrations, and a combined polarimeter with the same line of sight can correct fringe jump errors. A proof of the principle of the CO laser dispersion interferometer combined with the PEM polarimeter was recently conducted, where the phase shift and the polarization angle were successfully measured simultaneously. Standard deviations of the line-average density and the polarization angle measurements over 1 s are 9 × 10 m and 0.19°, respectively, with a time constant of 100 μs. Drifts of the zero point, which determine the resolution in steady-state operation, correspond to 0.25% and 1% of the phase shift and the Faraday rotation angle expected on ITER.

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Performance evaluation of short-wavelength FIR laser polarimeter with dual silicon photoelastic modulators

Akiyama

Kawahata

Okajima

et al. 2009

Plasma Devices and Operations

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Short wavelength far infrared laser polarimeter with silicon photoelastic modulators

Cited by 5 publications

References 27 publications

Progress in development of two color laser diagnostics for the ITER poloidal polarimeter

Progress in development of two color laser diagnostics for the ITER poloidal polarimeter

Design of a dispersion interferometer combined with a polarimeter to increase the electron density measurement reliability on ITER

Performance evaluation of short-wavelength FIR laser polarimeter with dual silicon photoelastic modulators

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