Development of a new two color far infrared laser interferometer for future fusion devices

Kawahata, K.; Tanaka, Kaoru; Tokuzawa, T.; Akiyama, Tsuyoshi; Ito, Y.; Okajima, S.; Nakayama, Keiichi I.; Wylde, Richard

doi:10.1063/1.1791748

Cited by 17 publications

(8 citation statements)

References 9 publications

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“…These two color laser oscillation lines enable us to construct a two color laser interferometer. 6 This two color interferometer system is a unique one compared with the conventional two color interferometer system, where two independent lasers are used to be combined: Figure 1 shows the conceptual design of the interferometer using a two color far infrared laser system. A MartinPuplett diplexer is placed in front of the laser output, since 57.2 and 46.7 m laser lines have different polarization.…”

Section: Introductionmentioning

confidence: 99%

Two color far infrared laser interferometer

Kawahata

Akiyama

Pavlichenko

et al. 2006

Review of Scientific Instruments

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Two color interferometer using a short wavelength far infrared laser has been developed for high performance plasmas on large helical device and for future fusion devices such as ITER. High power laser lines simultaneously oscillating at 57.2 and 47.6 m were achieved in a CO 2 -laser-pumped CH 3 OD laser. By introducing Ge:Ga photoconductive detectors operating at liquid He temperature, we have successfully detected two color beat signals ͑0.55 and 1.2 MHz͒ with excellent signal-to-noise ratio ͑ϳ40 dB͒. These beat signals were fed into phase comparators for phase measurement after passing through intermediate frequency bandpass filters. Two color far infraned laser interferometer work was successful in the demonstration of mechanical vibration compensation.

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Section: Introductionmentioning

confidence: 99%

Two color far infrared laser interferometer

Kawahata

Akiyama

Pavlichenko

et al. 2006

Review of Scientific Instruments

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“…The closest analogs of our two-wave interferometer are those designed at the Kurchatov Institute [13,14] and NIFS [15]. In [15], two methanol (CH 3 OD) lasers pumped by a ëé 2 laser and operating at wavelengths of 57.2 and 47.6 µm are used.…”

Section: Discussionmentioning

confidence: 99%

10.1007/s11452-008-3005-1

2010

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An upgraded diagnostics for measuring the electron density profile in the L-2M stellarator is proposed. The existing diagnostics employs an interferometer based on an HCN laser with a mechanical frequency shifter and unmagnetized InSb detectors cooled with liquid helium. It is proposed to replace the HCN laser with a water vapor laser operating simultaneously at two wavelengths (220 and 118 µ m). Being equipped with an anisotropic exit mirror, the water vapor laser allows the generation of orthogonally polarized, frequency-splitted modes at each of these wavelengths with a frequency difference of several tens of kilohertzs. Such a scheme makes it possible to get rid of the mechanical frequency shifter. Moreover, simultaneous measurements at two wavelengths allow one to reliably separate the phase increments introduced by the plasma electron component and by variations in the lengths of the interferometer arms. To take full advantage of this scheme, specially developed cryogenic receivers consisting of Ge and InSb photodetectors placed one after another will be used. To increase the response of the system near λ = 220 µ m, the InSb detector is placed in a ≈ 0.55-T magnetic field.

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“…Using these laser lines, optical constants (refractive index and absorption coefficient) of a chemical-vapor-deposited diamond etalon and a silicon etalon with high resistive have been measured to design windows and beam splitters (BS) [4]. So we have proposed a new two-color laser interferometer using 48and 57-pim CH30D lasers [5]. This two-color interferometer makes possible precise compensation of mechanical vibration.…”

Section: Introductionmentioning

confidence: 99%