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This study evaluated an effect of an coupling between the Faraday and Cotton-Mouton effect to a measurement signal of the Dodel-Kunz method which uses counter-circular-polarized probing-laser for measuring the Faraday effect. When the coupling is small (the Faraday effect is dominant and the characteristic eigenmodes are approximately circularly polarized), the measurement signal can be algebraically expressed and it is shown that the finite effect of the coupling is still significant. When the Faraday effect is not dominant, a numerical calculation is necessary. The numerical calculation under an ITER-like condition (Bt = 5.3 T, Ip = 15 MA, a = 2 m, ne = 1020 m-3 and λ = 119 μm) showed that difference between the pure Faraday rotation and the measurement signal of the Dodel-Kunz method was an order of one degree, which exceeds allowable error of ITER poloidal polarimeter. In conclusion, similar to other polarimeter techniques, the Dodel-Kunz method is not free from the coupling between the Faraday and Cotton-Mouton effect. [ABSTRACT FROM AUTHOR]

This study demonstrates the separation of the finite electron temperature on the plasma polarimetry in the magnetic confined fusion plasma for the first time. Approximate solutions of the transformed Stokes equation, including the relativistic effect, suggest that the orientation angle, θ, and ellipticity angle, [variant_greek_epsilon], of polarization state have different dependency on the electron density, ne, and the electron temperature, Te, and that the separation of ne and Te from θ and [variant_greek_epsilon] is possible in principle. We carry out the equilibrium and kinetic reconstruction of tokamak plasma when the central electron density was 1020 m-3, and the central electron temperatures were 5, 10, 20, and 30 keV. For both cases when a total plasma current, Ip, is known and when Ip is unknown, the profiles of plasma current density, j[lowercase_phi_synonym], ne, and Te are successfully reconstructed. The reconstruction of j[lowercase_phi_synonym] without the information of Ip indicates the new method of Ip measurement applicable to steady state operation of tokamak. [ABSTRACT FROM AUTHOR]

A new method for determining the plasma electron density using the fractional fringes on three-color interferometer is proposed. Integrated phase shift on each interferometer is derived without using the temporal history of the fractional fringes. The dependence on the fringe resolution and the electrical noise are simulated on the wavelengths of CO2 laser. Short-time integrations of the fractional fringes enhance the reliability of this method. [ABSTRACT FROM AUTHOR]

The infrared CO[sub 2] laser polarimetry for electron density measurement based on the tangential Faraday rotation has been progressed in JT-60U tokamak. The reliability of polarimetry in a pellet-injected plasma was confirmed. The Faraday rotation was measured with good angle resolution of ∼0.01° under the sufficiently fast temporal resolution of 4 ms. Electron density evaluated from the tangential Faraday rotation measured by polarimetry shows good agreement with that measured by interferometry for an identical probing laser beam. The long-time continuous measurement was successful with good stability and accuracy. The basic feasibility of the infrared CO[sub 2] laser polarimetry for electron density measurement in long-time and steady-state operation in large fusion devices was demonstrated. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Demonstrates the first measurement of the Faraday rotation of carbon dioxide laser wave propagating in toroidally tangential direction in the JT-60U tokamak plasma. Reliable detection of the polarization angle using photoelastic modulators; Accuracy of the measured polarization angle.

Describes the first operational results of the dual carbon dioxide laser polarimeter to measure Faraday rotation in large tokamaks. Components of the polarimeter; Photoelastic modulators utilized by each polarimeter; Successful measurement of the Faraday rotation by the JT-60U plasma even at a fast disruption.

Describes a dual carbon dioxide laser interferometer for measuring the electron density of tokamak plasmas. Description of the different wavelength oscillators; Advantages provided the system; density behavior during a fast disruption.

Proposes a two-color laser polarimeter on large tokamaks for electron density measurement based on the midplane Faraday rotation. Elimination of the Faraday rotation at vacuum windows from measured polarization angles; Photoelastic modulators used for stable polarization measurement.

A tangential chord CO[sub 2] laser interferometer for electron density measurement in the JT-60U tokamak is described. To compensate for a phase shift due to mirror vibrations, an IR-HeNe laser interferometer is introduced. Probe beams of the CO[sub 2] and the IR-HeNe lasers travel in a similar form for a distance of 100 m by utilizing relay optics. The effective phase resolution of the system is estimated to be 1/68 fringe, which corresponds to a line integrated density of 3.1 × 10[sup 18] m[sup -2]. An ultra-accurate phase comparator which has a 1/10[sup 4] fringe resolution is proposed to improve the capability of present and future interferometers. [ABSTRACT FROM AUTHOR]

Chemical vapor deposited diamond disks have been successfully applied as the vacuum windows for infrared CO[sub 2] laser interferometry and polarimetry used in electron density measurement in the JT-60U tokamak. In comparison with the conventional zinc–selenide windows, the Faraday rotation component of diamond windows was negligible. This results in an improvement of the Faraday rotation measurement of tokamak plasma by polarimetry. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Japan Domestic Agency (JADA) is responsible for six diagnostic systems in the ITER project. We have successfully developed a prototype instrumentation and control (I&C) system for the ITER divertor thermocouples system. The prototype I&C system includes a supervisory function, a sequencing management function, and a data acquisition function. The supervisory function, which was implemented using EPICS (Experimental Physics and Industrial Control System), manages internal operations for measurement such as health check of sensors. We developed a conversion tool from flowcharts to EPICS record source codes. The EPICS records generated by the conversion tool are used to trigger each operation step and to indicate the progress of the sequence. We also developed the sequencing management function that coordinates the execution of operation steps. Both the flowchart conversion tool and sequencing management function were developed to reduce designers’ mistakes and to ensure rapid development. The prototype I&C system for the DTC was tested. We confirmed that the I&C system performed satisfying the requirements. This validated design will be applied to other ITER diagnostic systems procured by JADA. [ABSTRACT FROM AUTHOR]

A new method of plasma electron density measurement using interferometric phases (fractional fringes) of an optical frequency comb interferometer is proposed. Using the characteristics of the optical frequency comb laser, high density measurement can be achieved without fringe counting errors. Simulations show that the short wavelength and wide wavelength range of the laser source and low noise in interferometric phases measurements are effective to reduce ambiguity of measured density.