Zeeman polarimetry measurement for edge current density determination using Li-beam probe on JT-60U

Journal Article · Mon Mar 15 04:00:00 EDT 2010 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3309793· OSTI ID:22053948

Kamiya, K; Fujita, T; Kojima, A; Kubo, H ^[1]

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1. Japan Atomic Energy Agency (JAEA), Naka, Ibaraki 311-0193 (Japan)

Zeeman polarimetry system using Li-beam probe has been developed for the edge current density measurement in the JT-60U tokamak, which measures the polarization angle {alpha} (related to the pitch angle of the magnetic field) by means of photoelastic modulators, etalons, and phase sensitive detection using digital lock-in amplifiers with the accuracy in the {alpha} of {Delta}{alpha}{approx}0.1 deg. The diagnostic has 20-channel viewing chords covering the plasma peripheral region of normalized minor radius r/a{approx}0.8-1 with a spatial resolution of up to {approx}1 cm. Li-beam injection with beam current of up to {approx}5 mA has been achieved. A new tuning method of the wavelength for the etalon has been demonstrated, scanning the beam acceleration voltage and keeping a beam current constant during a single shot. The peak wavelength of the etalon is adjusted in the direction to both blue- and redshifts by changing the angle of incidence and increasing the temperature, respectively. Time evolution of the edge current density profile has been determined for the current ramp experiment in the Ohmically heated discharges. In addition, the edge current density profile with the local peak of j{sub ped}{approx}0.15-0.25 MA/m{sup 2} at r/a{approx}0.9 has been identified in the H-mode plasma, which is correlated with large pressure gradient in the pedestal region.

• OSTI ID: 22053948
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 3 Vol. 81; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ACCURACY
BEAM CURRENTS
BEAM INJECTION
CURRENT DENSITY
H-MODE PLASMA CONFINEMENT
INCIDENCE ANGLE
INCLINATION
INTERFEROMETERS
JT-60U TOKAMAK
LITHIUM
LOCK-IN AMPLIFIERS
MAGNETIC FIELDS
PLASMA
POLARIMETRY
POLARIZATION
RED SHIFT
SPATIAL RESOLUTION
TUNING
WAVELENGTHS
ZEEMAN EFFECT