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

Akiyama, Tomohiro; Sirinelli, A.; Watts, Christopher; Shigin, P.; Vayakis, G.; Walsh, Mike

doi:10.1063/1.4962050

Cited by 18 publications

(18 citation statements)

References 12 publications

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“…The majority of HDI optics and electronics components are placed in a dedicated laser room and the probe beam propagates to the DIII-D tokamak along a fully enclosed beam duct. The total double-pass path length is approximately 100 m, which is comparable to that expected on ITER 9 . Due to the long beam path and proximity of several components to the tokamak, which causes significant motion during a discharge, active feedback alignment of the system is essential.…”

Section: Optical Setup On Diii-dsupporting

confidence: 55%

A heterodyne dispersion interferometer for wide bandwidth density measurements on DIII-D

Akiyama

Zeeland

Boivin

et al. 2018

Review of Scientific Instruments

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In order to improve both the density and particularly the temporal resolution beyond previous dispersion interferometers (DI), a heterodyne technique based on an acousto-optic (AO) cell has been added to the DI. A 40 MHz drive frequency for the AO cell allows density fluctuation measurements into the MHz range. A CO2 laser based heterodyne DI (HDI) installed on DIII-D has demonstrated that the HDI is capable of tracking the density evolution throughout DIII-D discharges, including disruption events and other rapid transient phenomena. The data also show good agreement with independent density measurements obtained with the existing DIII-D two-color interferometer. The HDI line-integrated density resolution sampled over a 1s interval is ~9×10 17 m-2. Density fluctuations induced by MHD instabilities are also successfully measured by the HDI.

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Section: Optical Setup On Diii-dsupporting

confidence: 55%

A heterodyne dispersion interferometer for wide bandwidth density measurements on DIII-D

Akiyama

Zeeland

Boivin

et al. 2018

Review of Scientific Instruments

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“…The dispersion interferometer does not require the optical-axis alignment of two different wavelengths, it does not depend on the laser conditions, does not have phase jumps, and does not require a reference channel to pass outside the plasma. The dispersion interferometer presently works in W7-X [35] and is planned for use in ITER [36,37]. The noise level of the CO 2 laser dispersion interferometer in LHD was 1.3 × 10 18 m −2 for the peak-to-peak value at 10 kHz sampling.…”

Section: Discussionmentioning

confidence: 99%

Development of Two-Color Laser Imaging Interferometer Using CO<sub>2 </sub>Laser and Quantum Cascade Laser in the Large Helical Device

Kinoshita

Tanaka

Takemura

et al. 2022

Plasma and Fusion Research

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CO 2 laser interferometers are a promising option for high-density plasma measurements. However, in lowand middle-density measurements, noise due to mechanical vibrations is a serious problem. To remove this noise, we developed a two-color laser imaging interferometer using a CO 2 laser and quantum cascade (QC) laser, called the CO 2 /QC laser imaging interferometer, through benchtop experiments and installed it in the Large Helical Device (LHD). Benchtop experiments provided optical design guidelines for the CO 2 /QC laser imaging interferometer to minimize the influence of the unstable output wavelength of the QC laser. The optical system in LHD was designed according to this guideline, and the vibration noise was successfully reduced to 2.80 × 10 18 m −3 . We also demonstrate measurement examples of hollowed and peaked electron density profiles evaluated using Abel inversion and macro-scale instability. This is the first study to present the measurement results of high-temperature plasma using a CO 2 /QC two-color laser interferometer. The study outcomes provide important insights for the development of two-color laser interferometers in future fusion devices. c

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“…At the end of the FOV, a 60 mm radius retroreflector was embedded at the bottom of a 500 mm depth hole on a blanket module (stainless steel). The retroreflector is used for a dispersion interferometer and polarimeter (DIP) [13]. The VSRS will share the hole on the wall with DIP, which also has a line of sight from the equatorial port 8.…”

Section: Inc) a 120mentioning

confidence: 99%

Ray Trace Study for Visible Spectroscopy Reference System (VSRS) Diagnostics in ITER

Kajita

Bock²,

Desjardins³

et al. 2019

Plasma and Fusion Research

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The visible spectroscopy reference system (VSRS) diagnostic will be used to measure the continuum visible light emitted from the plasma in ITER. Because the field of view of the VSRS system is aligned to a hole on a blanket module with a retroreflector on the bottom, which will be shared with an interferometer measurement, it has a potential to be free from the stray light, which may disturb signals for optical diagnostics in ITER. In this study, performance of the stray light reduction in the VSRS is investigated using a ray tracing simulation. We investigated the influences of the reflection property of the retroreflector and first mirror for the signal and stray light intensity.

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

Cited by 18 publications

References 12 publications

A heterodyne dispersion interferometer for wide bandwidth density measurements on DIII-D

A heterodyne dispersion interferometer for wide bandwidth density measurements on DIII-D

Development of Two-Color Laser Imaging Interferometer Using CO<sub>2 </sub>Laser and Quantum Cascade Laser in the Large Helical Device

Ray Trace Study for Visible Spectroscopy Reference System (VSRS) Diagnostics in ITER

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