Impurity toroidal rotation and transport in Alcator C-Mod ohmic high confinement mode plasmas

Abstract

Central toroidal rotation and impurity transport coefficients have been determined in Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] Ohmic high confinement mode (H-mode) plasmas from observations of x-ray emission following impurity injection. Rotation velocities up to 3×104 m/sec in the co-current direction have been observed in the center of the best Ohmic H-mode plasmas. Purely ohmic H-mode plasmas display many characteristics similar to ion cyclotron range of frequencies (ICRF) heated H-mode plasmas, including the scaling of the rotation velocity with plasma parameters and the formation of edge pedestals in the electron density and temperature profiles. Very long impurity confinement times (∼1 sec) are seen in edge localized mode-free (ELM-free) Ohmic H-modes and the inward impurity convection velocity profile has been determined to be close to the calculated neoclassical profile.

Dimensionless size scaling of intrinsic rotation in DIII-D

“…At C-Mod, Rice and colleagues did some of the first experiments on intrinsic rotation in diverted tokamaks [21][22][23]. These experimental measurements were made in the interior in minor radius and an on-axis toroidal velocity was usually reported.…”

“…The measurements of V ϕ were made using X-ray spectra from trace injection of argon, and their experiments over time have shown this to be a good indicator of the bulk ion core velocity in C-Mod [24]. A machine parameter scaling for V ϕ was found where the magnitude of the positive core toroidal velocity increased linearly with W/I p , where W is the total plasma stored energy and I p is the magnitude of the plasma current [21][22][23]. This is referred as "Rice scaling" for intrinsic rotation.…”

Energy levels and transition rates for helium-like ions withZ = 10–36

“…Spectral lines of helium-like ions are also prominent features in the X-ray spectra of tokamak plasmas and laser-produced plasmas. These features arise from impurity elements (e.g., Hsuan et al 1987;Bombarda et al 1988;Beiersdorfer et al 1995;Elton et al 2000;Rosmej et al 2002;Rice et al 1987Rice et al , 1999Rice et al , 2000Rice et al , 2014Rice et al , 2015. The relative intensities Full Tables 1 and 2 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A141 of spectral lines from the n = 2 shell to the ground state have been widely used in temperature and density diagnostics for solar plasma (e.g., McKenzie et al 1979;Wolfson et al 1983;Keenan et al 1984;Doyle & Keenan 1986) and tokamak plasmas (e.g., Källne et al 1983;Keenan et al 1989).…”

X-ray observations of medium Z H- and He-like ions with satellites from C-Mod tokamak plasmas

“…Presented in Fig.7 is a measured x-ray spectrum of transitions from the n = 2 level in He-like Ca 18+ and nearby satellites (dots) [18,30,34,35,15] for a 5.4 T deuterium discharge with <n e > = 0.6×10 20 /m 3 and T e0 = 3.5 keV. The resonance (w, 1s 2 1 S 0 -1s2p 1 P 1 , 3177.26 mÅ) and forbidden (z, 1s 2 1 S 0 -1s2p 3 S 1 , 3211.13 mÅ) lines dominate, and intercombination (x, 1s 2 1 S 0 -1s2p 3 P 2 , 3189.19 mÅ and y, 1s in addition to n = 2 satellites q, r and k (1s 2 2p 2 P 1/2 -1s2p 2 2 D 3/2 , 3206.5 mÅ) and unresolved higher n satellites labelled '3' and '4', with spectator electrons in the n = 3 and n = 4 levels, respectively.…”

“…Improvements in high resolution x-ray spectrometers have allowed the detailed study of spectra from medium Z hydrogen-like [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15] and helium-like [16,17,18,19,20,4,21,22,23,24,7,25,26,27,28,29,30,31,32,33,34,35,36,37,38,14,39,15] ions in high temperature plasmas. This is made possible by corresponding advances in atomic structure codes, which enables individual line identifications to be made.…”