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Title: Spitzer or neoclassical resistivity: A comparison between measured and model poloidal field profiles on PBX-M

Abstract

Direct measurements of the radial profile of the magnetic field line pitch on PBX-M coupled with model predictions of these profiles allow a critical comparison with the Spitzer and neoclassical models of plasma parallel resistivity. The measurements of the magnetic field line pitch are made by Motional Stark Effect polarimetry, while the model profiles are determined by solving the poloidal field diffusion equation in the TRANSP transport code using measured plasma profiles and assuming either Spitzer or neoclassical resistivity. The measured field pitch profiles were available for only seven cases, and the model profiles were distinguishable from each other in only three of those cases due to finite resistive diffusion times. The data in two of these three were best matched by the Spitzer model, especially in the inner half of the plasma. Portions of the measured pitch profiles for these two cases and the full profiles for other cases, however, departed significantly from both the Spitzer and neoclassical models, indicating a plasma resistivity profile different from either model.

Authors:
; ; ; ; ; ;  [1];  [2]
  1. Princeton Univ., NJ (United States). Plasma Physics Lab.
  2. Fusion Physics and Technologies, Torrance, CA (United States)
Publication Date:
Research Org.:
Princeton Univ., NJ (United States). Plasma Physics Lab.
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10115620
Report Number(s):
PPPL-2807
ON: DE92006818
DOE Contract Number:
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Jan 1992
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; COMPACT IGNITION TOKAMAK; MAGNETIC FIELDS; DIFFUSION; NEOCLASSICAL TRANSPORT THEORY; TEMPERATURE DISTRIBUTION; POLARIMETRY; PLASMA DIAGNOSTICS; ELECTRIC CONDUCTIVITY; 700310; 700430; PLASMA CONFINEMENT; MAGNET COILS AND FIELDS

Citation Formats

Kaye, S.M., Hatcher, R., Kaita, R., Kessel, C., LeBlanc, B., McCune, D.C., Paul, S., and Levinton, F.M. Spitzer or neoclassical resistivity: A comparison between measured and model poloidal field profiles on PBX-M. United States: N. p., 1992. Web. doi:10.2172/10115620.
Kaye, S.M., Hatcher, R., Kaita, R., Kessel, C., LeBlanc, B., McCune, D.C., Paul, S., & Levinton, F.M. Spitzer or neoclassical resistivity: A comparison between measured and model poloidal field profiles on PBX-M. United States. doi:10.2172/10115620.
Kaye, S.M., Hatcher, R., Kaita, R., Kessel, C., LeBlanc, B., McCune, D.C., Paul, S., and Levinton, F.M. Wed . "Spitzer or neoclassical resistivity: A comparison between measured and model poloidal field profiles on PBX-M". United States. doi:10.2172/10115620. https://www.osti.gov/servlets/purl/10115620.
@article{osti_10115620,
title = {Spitzer or neoclassical resistivity: A comparison between measured and model poloidal field profiles on PBX-M},
author = {Kaye, S.M. and Hatcher, R. and Kaita, R. and Kessel, C. and LeBlanc, B. and McCune, D.C. and Paul, S. and Levinton, F.M.},
abstractNote = {Direct measurements of the radial profile of the magnetic field line pitch on PBX-M coupled with model predictions of these profiles allow a critical comparison with the Spitzer and neoclassical models of plasma parallel resistivity. The measurements of the magnetic field line pitch are made by Motional Stark Effect polarimetry, while the model profiles are determined by solving the poloidal field diffusion equation in the TRANSP transport code using measured plasma profiles and assuming either Spitzer or neoclassical resistivity. The measured field pitch profiles were available for only seven cases, and the model profiles were distinguishable from each other in only three of those cases due to finite resistive diffusion times. The data in two of these three were best matched by the Spitzer model, especially in the inner half of the plasma. Portions of the measured pitch profiles for these two cases and the full profiles for other cases, however, departed significantly from both the Spitzer and neoclassical models, indicating a plasma resistivity profile different from either model.},
doi = {10.2172/10115620},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jan 01 00:00:00 EST 1992},
month = {Wed Jan 01 00:00:00 EST 1992}
}

Technical Report:

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  • Direct measurements of the radial profile of the magnetic field line pitch on PBX-M coupled with model predictions of these profiles allow a critical comparison with the Spitzer and neoclassical models of plasma parallel resistivity. The measurements of the magnetic field line pitch are made by Motional Stark Effect polarimetry, while the model profiles are determined by solving the poloidal field diffusion equation in the TRANSP transport code using measured plasma profiles and assuming either Spitzer or neoclassical resistivity. The measured field pitch profiles were available for only seven cases, and the model profiles were distinguishable from each other inmore » only three of those cases due to finite resistive diffusion times. The data in two of these three were best matched by the Spitzer model, especially in the inner half of the plasma. Portions of the measured pitch profiles for these two cases and the full profiles for other cases, however, departed significantly from both the Spitzer and neoclassical models, indicating a plasma resistivity profile different from either model.« less
  • Direct measurements of the radial profile of the magnetic field line pitch on PBX-M (Phys. Fluids B {bold 2}, 1271 (1990)), coupled with model predictions of these profiles allow a critical comparison with the Spitzer and neoclassical models of plasma parallel resistivity. The measurements of the magnetic field line pitch are made by motional Stark effect polarimetry, while the model profiles are determined by solving the poloidal field diffusion equation in the TRANSP transport code using measured plasma profiles and assuming either Spitzer or neoclassical resistivity. The measured field pitch profiles were available for only seven cases, and the modelmore » profiles were distinguishable from each other in only three of those cases due to finite resistive diffusion times. The data in two of these three were best matched by the Spitzer model, especially in the inner-half of the plasma. Portions of the measured pitch profiles for these two cases and the full profiles for other cases, however, departed significantly from both the Spitzer and neoclassical models, indicating a plasma resistivity profile different from either model.« less
  • Polarimetry measurements of the Doppler-shifted H/sub ..cap alpha../ emission from a hydrogen neutral beam on the PBX-M tokamak have been employed in a novel technique for obtaining q(0) and poloidal magnetic field profiles. The electric field from the beam particle motion across the magnetic field (E = V/sub beam/ /times/ B) causes a wavelength splitting of several angstroms, and polarization of the emitted radiation (Stark effect). Viewed transverse to the fields, the emission is linearly polarized with the angle of polarization related to the direction of the magnetic field. 14 refs., 5 figs.
  • Here, predictive understanding of plasma transport is a long-term goal of fusion research. This requires testing models of plasma rotation including poloidal rotation. The present experiment was motivated by recent poloidal rotation measurements on spherical tokamaks (NSTX and MAST) which showed that the poloidal rotation of C +6 is much closer to the neoclassical prediction than reported results in larger aspect ratio machines such as TFTR, DIII-D, JT-60U and JET working at significantly higher toroidal field and ion temperature. We investigated whether the difference in aspect ratio (1.44 on NSTX versus 2.7 on DIII-D) could explain this. We measured Cmore » +6 poloidal rotation in DIII-D under conditions which matched, as best possible, those in the NSTX experiment; we matched plasma current (0.65 MA), on-axis toroidal field (0.55T), minor radius (0.6 m), and outer flux surface shape as well as the density and temperature profiles. DIII-D results from this work also show reasonable agreement with neoclassical theory. Accordingly, the different aspect ratio does not explain the previously mentioned difference in poloidal rotation results.« less
  • Knowledge of poloidal velocity is necessary for the determination of the radial electric field, Er, which along with its gradient is linked to turbulence suppression and transport barrier formation. Recent measurements of poloidal flow on conventional tokamaks have been reported to be an order of magnitude larger than expected from neoclassical theory. In contrast, recent poloidal velocity measurements on the NSTX spherical torus [S. M. Kaye et al., Phys. Plasmas 8, 1977 (2001)] are near or below neoclassical estimates. A novel charge exchange recombination spectroscopy diagnostic is used, which features active and passive sets of up/down symmetric views to producemore » line-integrated poloidal velocity measurements that do not need atomic physics corrections. Local profiles are obtained with an inversion. Poloidal velocity measurements are compared with neoclassical values computed with the codes NCLASS [W. A. Houlberg et al., Phys. Plasmas 4, 3230 (1997)] and GTC-Neo [W. X. Wang, et al., Phys. Plasmas 13, 082501 (2006)], which has been updated to handle impurities. __________________________________________________« less