Polarimetry of motional Stark effect and determination of current profiles in DIII-D

Conference · Fri May 01 00:00:00 EDT 1992

OSTI ID:5103103

Wroblewski, D ^[1]; Lao, L L ^[2]

---

1. Lawrence Livermore National Lab., CA (United States)
2. General Atomics, San Diego, CA (United States)

The motional electric field E = v {times} B, where v is the velocity and B is the tokamak magnetic field, produces a strong Stark effect in spectral lines emitted by hydrogenic neutral beams. The tilt angle of the magnetic field line, a quantity related directly to the distribution of the plasma toroidal current, is deduced from a measurement of the direction of polarization of the Stark components. In the DIII-D tokamak, the Balmer-{alpha} line of deuterium emitted by one of the high-power heating beams is analyzed. A multichord polarimeter measures the magnetic field pitch angle at eight spatial locations covering {approximately}0.6 of the nominal plasma diameter at the midplane outboard side. The diagnostic offers 2 to 8 cm resolution in the major radius and 1 ms integration time. The accuracy of the measurement of the polarization direction necessary for an adequate reconstruction of the current profiles is obtained with the use of active polarizing elements which produce high frequency intensity modulation with an amplitude related to the direction of linear polarization of the plasma radiation. The current profiles in highly shaped (non-circular) plasmas cannot be determined solely from the tilt angle measurements because they do not provide any information about the shape of magnetic surfaces. Thus, the polarization measurement are used in conjunction with a large set of external magnetic measurements (magnetic field and flux probes, diamagnetic loops, and Rogowski coils) by the magnetic field equilibrium code EFIT, and provide a constraint on the possible solutions for the current profile.

• Research Organization: General Atomics, San Diego, CA (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC03-89ER51114; W-7405-ENG-48
• OSTI ID: 5103103
• Report Number(s): GA-A-20881; CONF-920362-34; ON: DE92016258
• Resource Relation: Conference: 9. topical conference on high-temperature plasma diagnostics, Santa Fe, NM (United States), 15-19 Mar 1992
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DOUBLET-3 DEVICE
PLASMA DIAGNOSTICS
NEUTRAL ATOM BEAM INJECTION
POLARIMETRY
CALIBRATION
ELECTRIC FIELDS
EMISSION SPECTRA
FIBER OPTICS
MAGNETIC FIELDS
MODULATION
MONOCHROMATORS
MULTI-CHANNEL ANALYZERS
POLARIZATION
STARK EFFECT
BEAM INJECTION
CLOSED PLASMA DEVICES
ELECTRONIC EQUIPMENT
EQUIPMENT
PULSE ANALYZERS
SPECTRA
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
700320* - Plasma Diagnostic Techniques & Instrumentation- (1992-)