Electron cyclotron emission diagnostics on the large helical device

The concept of digital correlation electron cyclotron emission (ECE) measurement is proposed for studying of the mesoscale phenomena. The recent progress in fast sampling and computing enables the acquisition of waveforms of intermediate frequency (IF) in the range of several gigahertz. Correlation analysis using an IF digitizing technique can be helpful for analyzing mesoscale phenomena. This paper discusses the concept and characteristics of the IF digitizing technique for correlation analysis, and presents an example of IF waveform acquisition of ECE.

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“…Such heterodyne detection is also used in the LHD [3,4]. A schematic diagram of the heterodyne radiometer used in LHD is shown as in Fig.…”

Section: Hardware Set-upmentioning

confidence: 99%

Digital Correlation ECE Measurement Technique with a Gigahertz Sampling Digitizer

Takahashi

Inagaki

Tokuzawa

et al. 2014

Plasma and Fusion Research

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“…Today, this is a routine technique for obtaining electron temperature profiles using a variety of instrument configurations. 25,26 …”

Section: I~v! ϭ Vmentioning

confidence: 99%

“…2 n e @n 2nϪ2~9 . 78 Other potential complicating effects such as harmonic overlap, relativistic broadening and downshifts, polarization scrambling, and nonthermal populations can occur and are discussed in the literature. 14,15,[31][32][33] In the case of relativistic downshifts, the effect has been suggested as a means of measuring the electron density distribution.…”

Section: Iib Theorymentioning

confidence: 99%

“…in Japan 25,[76][77][78] ; LHD is the world's largest heliotron-type device, with a complicated magnetic field configuration produced by 1 ϭ 20m ϭ 10 continuous helical coils and three pairs of poloidal coils. Table III briefly lists the ECE instruments and their relevant characteristics. Second-harmonic X-mode radiation is measured with both an FTS comprising a fast scanning Michelson interferometer and with a GPS.…”

Section: Iie2 Lhd Ece Systemsmentioning

confidence: 99%

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Chapter 3: Microwave Diagnostics

Luhmann

Bindslev

Park

et al. 2008

Fusion Science and Technology

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“…In addition to this, a TV Thomson scattering system has been introduced recently with the goal of the high spatial resolution. Also, three types of electron cyclotron emission (ECE) diagnostics have been installed, grating polychromator, radiometer and Michelson [20]. The ECE is proven as a reliable diagnostic for the temporal development of the electron temperature profile.…”

Section: ) Electron Density Diagnosticsmentioning

confidence: 99%

LHD Diagnostics Toward Steady-State Operation

Sudo

Peterson

Kawahata

et al. 2004

IEEE Trans. Plasma Sci.

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Abstract-The large helical device (LHD) is the world largest helical system having all superconducting coils. After completion of LHD in 1998, six experimental campaigns have been carried out successfully. The maximum stored energy, central electron temperature, and volume averaged beta value are 1.16 MJ, 10 keV, and 3.2%, respectively. The confinement time of the LHD plasma appears to be equivalent to that of tokamaks. One of the most important missions for LHD is to prove steady-state operation, which is also significant to international thermonuclear experimental reactor (ITER) and to future fusion reactors. LHD is quite appropriate for this purpose based upon the beneficial feature of a helical system, that is, no necessity of the plasma current. So far, the plasma discharge duration was achieved up to 150 s. The plasma density was kept constant by feedback control of gas puffing with real time information of the line density. The issue for demonstrating steady-state operation is whether divertor function to control particle and heat flux is effective enough. Relevant to this, LHD diagnostics should be consistent with the following: 1) continuous operation of main diagnostics during long-pulse operation for feedback control and physics understanding; 2) measurement of fraction of H, He, and impurities in the plasma; 3) heat removal and measure against possible damage or surface erosion of diagnostic components inside of the vacuum chamber; 4) data acquisition system for handling real time data display and a huge amount of data. Although there are already some achievements on the above subjects, there remain still several issues to be resolved.On the other hand, the long-pulse operation of the plasma gives benefits to the diagnostics. For example, the polarizing angle of ECE emission can be changed during the discharge, and the intensity dependence on the polarizing angle has been obtained. The spatial scanning of the neutral particle analyzer and the spectrometer can supply the spatial profiles of the fast neutral particle flux and the specific impurity lines.In this paper, the present status of these issues and future plans are described.

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Electron cyclotron emission diagnostics on the large helical device

Cited by 40 publications

References 14 publications

Digital Correlation ECE Measurement Technique with a Gigahertz Sampling Digitizer

Digital Correlation ECE Measurement Technique with a Gigahertz Sampling Digitizer

Chapter 3: Microwave Diagnostics

LHD Diagnostics Toward Steady-State Operation

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