Stainless steel grill used to inject LHRF power in Alcator C-Mod. Grill consists of four rows of 22 phased waveguides per row.
The vacuum power spectra vs parallel refractive index , launched by a single row of the LH coupler in Fig. 1 . The blue solid line, green dashed line, and the red dash-dotted line correspond to relative waveguide phasings of 60°, 90°, and 120°, respectively.
Layout of sightlines for the 32 chord, horizontally viewing hard x-ray camera on Alcator C-Mod.
Measured decrease in loop voltage vs time for increasing LH power levels. All traces correspond to a series of discharges in Alcator C-Mod, where and .
Change in loop voltage vs normalized power for a range of plasma and LHRF parameters in Alcator C-Mod [ , , ].
Normalized loop voltage drop vs normalized power for three different relative waveguide phasings. Solid circles correspond to 60° phasing (launched ), square symbols correspond to 90° phasing (launched ), and open circles correspond to 120° phasing (launched ).
Analysis of LHCD results from Alcator C-Mod using the Fisch–Karney theory (Ref. 23). Normalized power required to support the inductive energy in the plasma vs the wave parallel phase velocity normalized to the Dreicer velocity .
Value of parallel refractive index at absorption [ (absorbed)] vs the launched parallel refractive index [ (launched)] as derived from fitting the Alcator C-Mod LHCD data to the Fisch–Karney theory (see Fig. 7 ).
Time traces for a discharge in Alcator C-Mod where there is significant noninductive LH current drive. Top row of traces show the plasma current ( ) and peak electron density vs time ( ). Middle row of traces show the LH power ( ) and the peak electron temperature ( ) vs time ( ). Bottom row of traces show the plasma and loop voltage vs time ( ).
(a) Contours of the nonthermal LH-driven electron distribution function from a GENRAY-CQL3D simulation for the discharge parameters in Fig. 9 . Distribution function contours correspond to a normalized minor radius of . (b) Comparison of measured and simulated (without radial diffusion) hard x-ray spectra for the discharge in Fig. 9 at . Experimentally measured spectra are shown as solid lines and the simulated spectra are shown as dashed lines. The black, blue, and red curves correspond to the , , and detector energies, respectively.
(a) Comparison of LHRF deposition profiles from a GENRAY-CQL3D simulation of the C-Mod discharge in Fig. 9 at . The blue curve corresponds to the CQL3D simulation without radial diffusion and the red curve corresponds to the CQL3D simulation with a radial diffusion operator of the form given by Eqs. (7) with . (b) Comparison of LHRF current density profiles from the GENRAY-CQL3D simulation shown in (a). The blue curve corresponds to the CQL3D simulation without radial diffusion and the red curve corresponds to the CQL3D simulation with radial diffusion. (c) Comparison of measured and simulated hard x-ray spectra. The solid black line corresponds to the measured spectra at (the detector bin), the solid blue line corresponds to the simulated spectra without diffusion, and the dashed blue line corresponds to the simulated spectra with radial diffusion.
Measurements of LH current profile modification in Alcator C-Mod from the MSE diagnostic. The red traces correspond to an ohmic reference plasma with no LH power and the tan, blue, and green traces correspond to three consecutive discharges with LH power applied at the level. Time traces for the LH power and loop voltage are shown in the top panels and time traces for the MSE measurement of pitch angle are shown in the middle and bottom panels for four channels corresponding to and .
(a) Electron density from Thomson scattering vs normalized radius for discharge 1070828018 at . (b) LH wave accessibility for 75° phasing vs major radial position ( ), using Eq. (6) , the density profile in (a), and the EFIT equilibrium reconstruction at .
(a) Comparison of the measured current density profile from the MSE diagnostic (red diamonds) with the simulated current density (ohmic plus LH) from CQL3D (blue line) for discharge 1070828018 at . Also shown for reference is the LH current density profile from a CQL3D simulation corresponding to a zero DC electric field. (b) Comparison of the measured and simulated hard x-ray spectra for discharge 1070828018 at . The experimentally measured spectrum at (the energy bin) corresponds to the solid black line and the simulated spectrum corresponds to the solid blue line and includes radial diffusion.
Full-wave LH field simulation for Alcator C-Mod plasma [ , , , ]. The simulation was performed using the parallel TORIC-LH solver with 980 radial elements and 1023 poloidal modes. Shown are the contours of the .
(a) LHRF power density profile from the TORIC-LH field solver for the Alcator C-Mod plasma shown in Fig. 16 and using linear electron Landau damping. (b) LHRF power density profile from a GENRAY simulation of the C-Mod plasma in Fig. 12(a) using a narrow distribution of rays with linear electron Landau damping. The power densities in (a) and (b) are normalized to of absorbed power.
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