Publications
Showing 57 results for Author: Morgan W. Shafer
Sep, 2014
Journal
Impact of plasma response on plasma displacements in DIII-D during application of external 3D perturbations
The effects of applied 3D resonant magnetic perturbations are modelled with and without self-consistent plasma response. The plasma response is calculated using a linear two-fluid model. A synthetic diagnostic is used to simulate soft x-ray (SXR) emission within the steep gradient region of the pedestal, 0.98 > ψ > 0.94. Two methods for simulating the SXR emission given th…
Sep, 2013
Conference Paper
Soft X-Ray Imaging Design and Analysis Methods on DIII-D
A new tangential 2D Soft X-Ray Imaging System (SXRIS) is being designed to examine the edge magnetic island structure in the lower X-point region of DIII-D. A synthetic diagnostic calculation coupled to 3D emissivity estimates is used to generate phantom images. Phillips-Tikhonov regularization is used to invert the phantom images for comparison to the original emissivity…
Jul, 2013
Journal
Role of plasma response in displacements of the tokamak edge due to applied non-axisymmetric fields
Linear, two-fluid, resistive modelling of the plasma response to applied non-axisymmetric fields shows significant displacement of edge temperature and density profiles. The calculated displacements, often of 2 cm or more in H-mode pedestals with parameters appropriate to DIII-D, are due to the helical distortions resulting from stable edge modes being driven to finite amp…
Aug, 2012
Journal
2D properties of core turbulence on DIII-D and comparison to gyrokinetic simulations
Quantitative 2D characteristics of localized density fluctuations are presented over the range of 0.3 < r/a < 0.9 in L-mode plasmas on DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)]. Broadband density fluctuations increase in amplitude from (n) over tilde /n < 0.5% in the deep core to (n) over tilde /n similar to 2.5% near the outer region. The observed Doppler-shift du…
Mar, 2012
Journal
Wide-field turbulence imaging with beam emission spectroscopy
Imaging of the size, shape, time-averaged, and time-resolved dynamics of long-wavelength density turbulence structures is accomplished with an expanded, high-sensitivity, wide-field beam emission spectroscopy (BES) diagnostic on DIII-D. A 64-channel BES system is configured with an 8 X 8 grid of discrete channels that image an approximately 7 X 9 cm region at the outboard…
Sep, 2011
Journal
2D soft x-ray system on DIII-D for imaging the magnetic topology in the pedestal region
A new tangential two-dimensional soft x-ray imaging system (SXRIS) is being designed to examine the edge island structure in the lower X-point region of DIII-D. Plasma shielding and/or amplification of the calculated vacuum islands may play a role in the suppression of edge-localized modes via resonant magnetic perturbations (RMPs). The SXRIS is intended to improve the und…
Sep, 2011
Journal
Simulation of a tangential soft x-ray imaging system
Tangentially viewing soft x-ray (SXR) cameras are capable of detecting nonaxisymmetric plasma structures in magnetically confined plasmas. They are particularly useful for studying stationary perturbations or phenomenon that occur on a timescale faster than the plasma rotation period. Tangential SXR camera diagnostics are planned for the DIII-D and NSTX tokamaks to elucida…