Transport with reversed shear in the National Spherical Torus Experiment

Levinton, F. M.; Yuh, H.; Bell, M. G.; Bell, R. E.; Delgado-Aparicio, L.; Finkenthal, M.; Fredrickson, E. D.; Gates, D. A.; Kaye, S. M.; LeBlanc, B. P.; Maingi, R.; Menard, J. E.; Mikkelsen, D.; Mueller, D.; Raman, R.; Rewoldt, G.; Sabbagh, S. A.; Stutman, D.; Tritz, K.; Wang, W.
May 2007
Physics of Plasmas;May2007, Vol. 14 Issue 5, p056119
Academic Journal
In the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)], plasmas with strongly reversed magnetic shear, s≡(r/q)(dq/dr)<0, in the plasma core exhibit a marked improvement in electron confinement compared to otherwise similar plasmas with positive or only weakly reversed magnetic shear. The q profile itself is determined by the early evolution of the plasma current, the plasma cross section, and the neutral-beam heating power. In the region of shear reversal, the electron thermal diffusivity can be significantly reduced. Detailed experimental investigation of this phenomenon has been made possible by the successful development of a motional Stark effect (MSE) polarimetry diagnostic suitable for the low magnetic field in NSTX, typically 0.35–0.55 T. Measurements of the electron and ion temperature, density, and plasma toroidal rotation profiles are also available with high spatial and temporal resolution for analysis of the plasma transport properties.


Related Articles

  • Measurements of the internal magnetic field on DIII-D using intensity and spacing of the motional Stark multiplet. Pablant, N. A.; Burrell, K. H.; Groebner, R. J.; Kaplan, D. H.; Holcomb, C. T. // Review of Scientific Instruments;Oct2008, Vol. 79 Issue 10, p10F517 

    We describe a version of a motional Stark effect (MSE) diagnostic based on the relative line intensities and spacing of Stark split Dα emission from the neutral beams. This system, named B-Stark, has been recently installed on the DIII-D tokamak. To find the magnetic pitch angle, we use the...

  • Measurements of the internal magnetic field using the B-Stark motional Stark effect diagnostic on DIII-D (inivited). Pablant, N. A.; Burrell, K. H.; Groebner, R. J.; Holcomb, C. T.; Kaplan, D. H. // Review of Scientific Instruments;Oct2010, Vol. 81 Issue 10, p10D729 

    Results are presented from the B-Stark diagnostic installed on the DIII-D tokamak. This diagnostic provides measurements of the magnitude and direction of the internal magnetic field. The B-Stark system is a version of a motional Stark effect (MSE) diagnostic based on the relative line...

  • Grating spectrometer system for beam emission spectroscopy diagnostics using high-energy negative-ion-based neutral beam injection on LHD. Kado, S.; Oishi, T.; Yoshinuma, M.; Ida, K. // Review of Scientific Instruments;Oct2010, Vol. 81 Issue 10, p10D720 

    A beam emission spectroscopy (BES) system was developed for density gradient and fluctuation diagnostics in the Large Helical Device (LHD). In order to cover the large Doppler shift of the Hα beam emission because of the high-energy negative-ion-based neutral beam atom (acceleration voltage...

  • Motional Stark effect diagnostic expansion on DIII-D for enhanced current and Er profile measurements. Holcomb, C. T.; Makowski, M. A.; Jayakumar, R. J.; Allen, S. A.; Ellis, R. M.; Geer, R.; Behne, D.; Morris, K. L.; Seppala, L. G.; Moller, J. M. // Review of Scientific Instruments;Oct2006, Vol. 77 Issue 10, p10E506 

    The motional Stark effect (MSE) diagnostic on DIII-D has been expanded to take advantage of a change in the neutral beam geometry, adding 24 new MSE channels viewing a beam injected counter to the plasma current. When data from these channels are used with those from two older MSE arrays viewing...

  • 3D numerical simulations of negative hydrogen ion extraction using realistic plasma parameters, geometry of the extraction aperture and full 3D magnetic field map. Mochalskyy, S.; Wunderlich, D.; Ruf, B.; Franzen, P.; Fantz, U.; Minea, T. // Review of Scientific Instruments;2014, Vol. 85 Issue 2, p1 

    Decreasing the co-extracted electron current while simultaneously keeping negative ion (NI) current sufficiently high is a crucial issue on the development plasma source system for ITER Neutral Beam Injector. To support finding the best extraction conditions the 3D Particle-in-Cell Monte Carlo...

  • Development of negative ion extractor in the high-power and long-pulse negative ion source for fusion application. Kashiwagi, M.; Umeda, N.; Tobari, H.; Kojima, A.; Yoshida, M.; Taniguchi, M.; Dairaku, M.; Maejima, T.; Yamanaka, H.; Watanabe, K.; Inoue, T.; Hanada, M. // Review of Scientific Instruments;2014, Vol. 85 Issue 2, p1 

    High power and long-pulse negative ion extractor, which is composed of the plasma grid (PG) and the extraction grid (EXG), is newly developed toward the neutral beam injector for heating and current drive of future fusion machines such as ITER, JT-60 Super Advanced and DEMO reactor. The PG is...

  • Simulation And Design Of A Reflection Magnet For The EAST Neutral Beam System. Zhen, Liang Li; Dong, Hu Chun // AIP Conference Proceedings;9/26/2011, Vol. 1390 Issue 1, p650 

    The simulation and design of a reflection magnet to be installed in the Experimental Advanced Superconducting Tokamak (EAST) neutral beam injection system are reported. A parametric design and simulation for the reflection magnet was carried out. For a deuterium beam with 42 cm as the bending...

  • Heat pulse propagation across the rational surface in a large helical device plasma with counter-neutral beam injection. Yakovlev, M.; Inagaki, S.; Shimozuma, T.; Kubo, S.; Morisaki, T.; Nagayama, Y.; Kawahata, K.; Komori, A. // Physics of Plasmas;Sep2005, Vol. 12 Issue 9, p092506 

    Core electron temperature profile flattening is observed in a large helical device [A. Iiyoshi et al. Nucl. Fusion 39, 1245 (1999)] inward shifted plasma with counter-neutral beam injection. To study this phenomenon, heat pulse experiments are performed by on-axis electron cyclotron heating...

  • Study of Negative Hydrogen Ion Beam Optics Using the 3D3V PIC Model. Miyamoto, K.; Nishioka, S.; Goto, I.; Hatayama, A.; Hanada, M.; Kojima, A. // AIP Conference Proceedings;2015, Vol. 1655 Issue 1, p1 

    The mechanism of negative ion extraction under real conditions with the complex magnetic field is studied by using the 3D PIC simulation code. The extraction region of the negative ion source for the negative ion based neutral beam injection system in fusion reactors is modelled. It is shown...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics