Active spectroscopy measurements of the Deuterium temperature, rotation, and density in the pedestal region of the DIII-D tokamak

Shaun Haskey

Princeton Plasma Physics Laboratory

Friday, March 13, 2020

3:00pm

NW17-218

PSFC Seminars

Abstract: Main-ion charge exchange recombination spectroscopy (MICER) [1,2] uses the neutral beam induced D-alpha emission spectrum to determine the local deuterium ion (D+) temperature, rotation and density, as well as several beam and equilibrium properties from the neutral beam emission. An edge MICER system consisting of 16 densely packed sightlines was installed on DIII-D extending the MICER technique from the core to the pedestal and steep gradient region of H-mode plasmas where the D+ and commonly measured impurity ion properties can differ significantly. A combination of iterative collisional radiative modeling techniques and greatly accelerated spectral fitting algorithms allowed the extension of this diagnostic technique to the plasma edge where the steep gradients introduce significant diagnostic challenges that require employing direct synthetic diagnostic modeling. Data from a wide range of plasma conditions has been acquired uncovering sometimes large temperature differences between D+ and impurity ions near the separatrix, inwardly shifted C6+ density pedestals, and rapid co-Ip D+ edge rotation. These observations provide significantly better experimental data for testing models and improving understanding in areas such as ion thermal transport and intrinsic rotation. For example the D+ temperature measurements resolve inconsistencies such as negative ion heat fluxes near the plasma edge, which are sometimes inferred when using the historical assumption that the impurity ion temperature is a good proxy for the D+ temperature. The measurements and analysis demonstrate the state of the art in active spectroscopy and integrated modeling for diagnosing fusion plasmas and the importance, despite the difficulties, of direct D+ measurements at the plasma edge.
[1] B.A Grierson, RSI, 2012
[2] S.R Haskey, RSI, 2018

Bio: Dr. Shaun R. Haskey is a research physicist for the Princeton Plasma Physics Laboratory (PPPL) based at the DIII-D tokamak in San Diego, CA. Shaun graduated from the University of Western Australia in 2006 with a B. Eng (hons) and B. Comm. After graduating he worked for a few years on oil rigs as a wireline field engineer for Schlumberger before going back to university to start a PhD at the Australian National University (ANU) under the supervision of Dr Boyd Blackwell, Dr John Howard, and Dr Matthew Hole. His thesis work involved developing Mirnov probe and high speed imaging systems to diagnose Alfven eigenmodes in the H-1 heliac, and modeling of 3D field physics on DIII-D. Having completed a doctoral degree at ANU, Shaun accepted the position of associate physicist at PPPL working with Dr. Brian Grierson at DIII-D on his DOE early career research program award: “Exploration of main-ion properties at the boundary of fusion reactors”. His work as an associate researcher focused on extending the main-ion charge exchange technique to the H-mode pedestal region. As a staff physicist, his research has continued to centre around improving the measurement capabilities of the main-ion CER system and using these measurements to better understand transport in the edge region of high performance tokamak plasmas.