Electron Cyclotron Emission Diagnostic Systems

[Objective]
Objective of electron cyclotron emission (ECE) diagnostic systems is to obtain time evolution of electron temperature with high temporal (~microsec) and spatial (~1 cm) resolutions.

The ECE diagnostic systems are composed of the following three systems:

Fourier Transform Spectrometer system (FTS),
Grating Polychromator System (GPS),
Heterodyne Radiometer System (HRS).
FTS is absolutely calibrated using liquid nitrogen, and GPS and HRS are relatively calibrated using the FTS data.

[Specifications]
Antennas for the ECE measurement are located at P14 and P17 sections, which are 60 degrees apart in toroidal direction. Transmission line in the torus hall is shown in Fig. 1.
ECE from the JT-60U plasma is transmitted through corrugated circular waveguides (diameter: 63.5 mm) and smooth-wall rectangular waveguides (WR-284). The transmission line, whose total length is about 40 m, goes to the diagnostic room outside the torus hall.

Transmission line in the diagnostic room is shown in Fig. 2. Two power dividers are used to lead the ECE to FTS, GPS and HRS. A highpass filter to reject electron cyclotron heating (ECH) wave (f=110 GHz) is also inserted. In addition, grating lowpass filters are installed in the GPS transmission line to reject spurious ECE.

ECE ranging from 100 to 300 GHz is measured with these systems, and second harmonic ECE is used for electron temperature measurement. Specifications of the ECE systems are shown in Table 1.


Fig. 1: ECE transmission line in the torus hall.

Fig. 2 : Layout of ECE diagnostic systems in the diagnostic room.
Transmission line from the P17 port is connected to the HRS transmission line depending on experimental schedule.


Table 1: Specifications of FTS, GPS and HRS

FTS

GPS

HRS
Temporal resolution (max.)

~25 ms

20 (1) microsec

20 (1) microsec
Frequency range [GHz]

100-800

100-300

152-200;
102-124
Frequency resolution [GHz]

3.66

1.3-2

0.5
Spatial resolution (for B=4T) [cm]

5.6

2.0

1.2
Number of channels

512

40

48
Calibration

Absolute

Relative

Relative


[ECE data analysis]
Analysis using ECE data has been extensively performed in collaboration with Daido Institute of Technology. Research topics are as follows:

- Effect of relativistic frequency down-shift on ECE measurement
- Adaptive neural network for detection of a sawtooth crash
- Singular value decomposition for separation of perturbative temperature component
- Spectrum estimate from FTS interferograms using maximum entropy method

References

* Review of ECE Diagnostic Systems
[1] M. Sato, S. Ishida, N. Isei, A. Isayama, H. Shirai, T. Oyevaar, M. Teranishi, N. Iwama and K. Uchino:
'Measurements and Analysis of Electron Cyclotron Emission in JT-60U', Fusion Eng. Design 34-35 (1997) 477.
[2] N. Isei, A. Isayama, S. Ishida, M. Sato, T. Oikawa, T. Fukuda, A. Nagashima, N. Iwama and JT-60 Team:
'Electron Cyclotron Emission Measurements in JT-60U', Fusion Eng. Design 53 (2001) 213.

* Fourier Transform Spectrometer System
[3] M. Sato, H. Yokomizo and A. Nagashima:
'Fourier Transform Spectrometer System on JT-60', Kakuyugo Kenkyu (J. Plasma Fusion Research) Supplement, 59 (1988) 47 [in Japanese].

* Grating Polychromator System
[4] S. Ishida, A. Nagashima, M. Sato, N. Isei and T. Matoba:
'Twenty-Channel Grating Polychromator Diagnostic System for Electron Cyclotron Emission Measurements', Rev. Sci. Instrum. 61 (1990) 2834.
[5] A. Isayama, N. Isei, S. Ishida and M. Sato:
' A 20-channel Electron Cyclotron Emission Detection System for a Grating Polychromator in JT-60U', Rev. Sci. Instrum. 73 (2002) 1165.

* Heterodyne Radiometer System
[6] N. Isei, M. Sato, S. Ishida, K. Uchino, A. Nagashima, T. Matoba and T. Oyevaar:
'Development of 180 GHz Heterodyne Radiometer for Electron Cyclotron Emission Measurement in JT-60U', Rev. Sci. Instrum. 66 (1995) 413.
[7] A. Isayama, N. Isei, S. Ishida, M. Sato, Y. Kamada, S. Ide, Y. Ikeda, K. Takahashi, K. Kajiwara, K. Hamamatsu and JT-60 Team:
'Electron Temperature Perturbations Measured by Electron Cyclotron Emission Diagnostic Systems in JT-60U', Fusion Eng. Design 53 (2001) 129.

* Grating filter for GPS
[8] M. Sato, N. Isei and S. Ishida:
'Grating Filter for Grating Polychromator on Measurement of Electron Temperature Profile from Second Harmonic Electron Cyclotron Emission', J. Plasma Fusion Res. 71 (1995) 748 [in Japanese].

* ECE Data Analysis
[9] M. Sato, S. Ishida and N. Isei:
'Relativistic Broadening Effect on Application of Electron Cyclotron Emission Measurements to High Temperature Tenuous Tokamak Plasma', J. Phys. Soc. Japan 62 (1993) 3106.
[10] M. Sato, N. Isei and S. Ishida:
'Relativistic Down-Shift Frequency Effect on the Application of Electron Cyclotron Emission Measurements to Medium Temperature Tokamak Plasmas', Jpn. J. Appl. Phys. 34 (1995) L708.
[11] M. Sato, N. Isei, S. Ishida and A. Isayama:
'Effects of Relativistic Frequency Down-Shift and Optical Thickness on Measurements of Electron Temperature Profile from Electron Cyclotron Emission in Medium Temperature Tokamak Plasmas', J. Phys. Soc. Jpn. 67 (1998) 3090.
[12] A. Isayama, Y. Kamada, T. Ozeki and N. Isei:
'Measurement of Magnetic Island Width in Long-pulse, High-beta_N Discharges in JT-60U', Plasma Phys. Control. Fusion 41 (1999) 35.
[13] M. Sato, N. Isei, A. Isayama and S. Ishida:
'Effects of Polarization Change on the Measurement of Electron Temperature Profile from ECE in Tokamak Plasma', Fusion Eng. Design 53 (2001) 161.
[14] A. Isayama, N. Iwama, Y. Hosoda, S. Satake, N. Isei, S. Ishida and M. Sato:
'Singular Value Decomposition Analysis of Multichannel Electron Cyclotron Emission Signals of Tokamak Plasma', Jpn. J. Appl. Phys. 42 (2003) L329.
[15] A. Isayama, N. Iwama, T. Showa, Y. Hosoda, N. Isei, S. Ishida and M. Sato:
'Maximum Entropy Estimation of Electron Cyclotron Emission Spectra from Incomplete Interferograms in ELMy H-mode Tokamak Experiment', Jpn. J. Appl. Phys. 42 (2003) 5787.
[16] M. Sato, A. Isayama, N. Iwama and K. Kawahata:
'Feasibility of Electron Density Measurement Using Relativistic Downshift of Electron Cyclotron Emission in Tokamak Plasmas', Jpn. J. Appl. Phys. 44 (2005) L672.
[17] A. Isayama, N. Oyama, H. Urano and the JT-60 Team:
'Measurement of Toroidal Structure of Electron Temperature with Electron Cyclotron Emission Diagnostic in JT-60U', Proc. 21st IEEE/NPSS Symposium on Fusion Engineering 2005 (SOFE2005).