Two-dimensional phase contrast imaging for local turbulence measurements in large helical device (invited)

Journal Article · Wed Oct 15 00:00:00 EDT 2008 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.2988821· OSTI ID:21266528

Tanaka, K; Michael, C A; Kawahata, K; Akiyama, T; Tokuzawa, T ^[1]; Vyacheslavov, L N; Sanin, A L ^[2]; Okajima, S ^[3]

---

1. National Institute for Fusion Science, Toki 509-5292 (Japan)
2. Budker Institute of Nuclear Physics, 630090, Novosibirsk (Russian Federation)
3. School of Engineering, Chubu University, Kasugai 487-8501 (Japan)

Two-dimensional phase contrast imaging (2D) installed on the large helical device (LHD) is a unique diagnostic for local turbulence measurements. A 10.6 {mu}m infrared CO{sub 2} laser and 6x8 channel HgCdTe 2D detector are used. The length of the scattering volume is larger than plasma size. However, the asymmetry of turbulence structure with respect to the magnetic field and magnetic shear make local turbulence measurements possible. From a 2D image of the integrated fluctuations, the spatial cross-correlation function was estimated using time domain correlation analysis, then, the integrated 2D k-spectrum is obtained using maximum entropy method. The 2D k-spectrum is converted from Cartesian coordinates to cylindrical coordinates. Finally, the angle in cylindrical coordinate is converted to flux surface labels. The fluctuation profile over almost the entire plasma diameter can be obtained at a single moment. The measurable k-region can be varied by adjusting the detection optics. Presently, k=0.1-1.0 mm{sup -1} can be measured which is expected region of ion temperature gradient modes and trapped electron mode in LHD. The spatial resolution is 10%-50% of the minor radius.

• OSTI ID: 21266528
• Journal Information: Review of Scientific Instruments, Vol. 79, Issue 10; Conference: HTPD08: 17. topical conference on high-temperature plasma diagnostics, Albuquerque, NM (United States), 11-15 May 2008; Other Information: DOI: 10.1063/1.2988821; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CALCULATION METHODS
CARBON DIOXIDE LASERS
CARTESIAN COORDINATES
CORRELATION FUNCTIONS
CYLINDRICAL CONFIGURATION
ENTROPY
FLUCTUATIONS
ION TEMPERATURE
LHD DEVICE
MAGNETIC FIELDS
MAGNETIC SURFACES
PLASMA
PLASMA DIAGNOSTICS
SPATIAL RESOLUTION
STELLARATORS
TEMPERATURE GRADIENTS
TRAPPED ELECTRONS
TURBULENCE
TWO-DIMENSIONAL CALCULATIONS