Current HSX Graduate Students
- Laurie Stephey
- Laurie is currently studying plasma fueling and the HSX neutral
population. She uses H-Alpha measurements and the DEGAS and DEGAS 2
neutral Monte-Carlo codes to study the 3D neutral particle density,
radial particle flux, and impacts of various fueling scenarios in HSX.
Her work also includes looking at the particle and energy balance at
limiters placed at the edge of the HSX plasmas
- Carson Cook
- Carson is working on the SIESTA (Spectral Iterative Equilibrium
Solver for Toroidal Applications) code development project with Steve
Hirshman and Raul Sanchez of ORNL. SIESTA is a magnetohydrodynamic
equilibrium code used for modeling toroidal plasmas in 3D systems.
Unlike VMEC, SIESTA does not assume nested magnetic flux surfaces, so
equilibria involving magnetic islands and stochastic regions can be
computed. The code is very scalable, a necessary feature for
ITER-relevant calculations. SIESTA will be extremely useful for
equilibrium analysis in perturbed tokamaks and stellarator modeling and
- Jason Smoniewski
- Jason is studying flows in HSX and the effects of viscosity and
symmetry on the determination of the flows and the radial electric field
in a stellarator.
- Adrian Akerson
- Jason is studying the edges of the plasmas in HSX, with a strong
emphasis on divertor flows, particle edge fluxes and edge plasma
parameters. In particular, comparisons and verifications of models of
the plasma divertors (EMC3-EIRENE) which at present do not include the
effects of local electric fields on the flows and particle fluxes.
- Carlos Ruiz
- Carlos is studying the the diagnostic neutral beam used in HSX for
CHERS flow measurements which is intended for use in Motional Stark
Effect determination of the plasma electric field.
- Fernando Castillo
- Fernando is continuing the work into impurity injection into HSX using
the YAG laser blow off equipment. Previous stellarator impurity
injection experiments in other devices have seen discrepancies in
impurity flows and accumulations as predicted by neoclassical models,
and seen in other non-stellarator devices.
- Tom Dobbins
- Tom is implementing a polarimetry system to evaluate the Stark shift
from the diagnostic Hydrogen neutral beam to allow better Electric field
- Stefan Gerhardt
- Stefan's research on HSX concentrated on examining flows and flow
damping in HSX which because of the quasi-symmetry was predicted to
allow flows similar to tokamaks.
- Stefan received his PhD in 2004, and is currently the Principal
Research Physicist at the Princeton Plasma Physics Lab in Princeton,
- John Canik
- John studied the effects of quasisymmetry on particle and heat
transport in HSX. He did this by measuring the plasma density and
temperature profiles using a Thomson scattering system. He also
performed extensive three-dimensional modeling of the neutral gas in
HSX plasma, which has yielded the particle source rate and neutral
- John received his Ph.D. in Spring of 2007 and went to work at Oak
Ridge National Laboratory under a prestigious Wigner Fellowship. John
now heads the ORNL plasma physics theory group.
- Walter Guttenfelder
- Walter's research on HSX concentrated on examining fluctuations and
anomalous transport in HSX especially through comparisons of edge
fluctuations measurements with 3-D gyrokinetic modeling.
- Walter received his PhD in the Winter of 2007, and currently works
at the Princeton Plasma Physics Lab in Princeton, NJ
- Ali's research on HSX concentrated on examining
superthermal electron dynamics in HSX especially through hard X-ray
measurements of the electron superthermal tail produced through second
harmonic X-mode ECRH.
- Ali received his PhD in the 2005, and currently works as an
Associate Professor at Zewail City of Science and Technology, Egypt
- Jeremy Lore
- Jeremy's focus area, during his time at HSX, was stellarator
transport, specifically the measurement and modeling of transport at
HSX. Jeremy currently developed the PENTA code with Don Spong from
ORNL, which calculates neoclassical transport quantities in
stellarators or tokamaks while conserving parallel momentum.
Neoclassical calculations predict a large "electron root" radial
electric field (Er) in the core of HSX plasmas, with strong radial
shear. The neoclassical simulations, coupled with turbulent transport
calculations performed by Walter Guttenfelder have been successful in
simulating the strongly peaked electron temperature profiles measured
during ECR heating. The predicted electric fields and in-surface flows
will be compared to ChERS measurements in the near future.
- In 2006 Jeremy implemented a displacement sensor system on HSX and
performed structural modeling and testing to ensure safe operation at
B=1T. Jeremy also performed analysis of data from the Thomson
- Jeremy received his PhD in the Spring of 2010, and currently works
at the Oak Ridge National Lab
- John Schmitt
- John worked on the design, installation, and analysis of the
magnetic diagnostics on the HSX stellarator in order to measure the
the equilibrium plasma currents present during the plasma discharge.
The pressure-driven Pfirsch-Schluter current is helical in nature
because of lack of toroidal curvature in the QHS magnetic spectrum,
and reduced by the high effective transform (3). The net toroidal
current is predominantly bootstrap-driven. The bootstrap current is
modeled by PENTA, and the time and spatial evolution is modeled by a
diffusion equation that includes the 3-D nature of the plasma column.
- John received his PhD in 2011 and currently works at the Princeton
Plasma Physics Laboratory in Princeton, NJ.
- Alexis Briesemeister
- Alexis explored the effects of quasi-symmetry on flows. To do this
she led the implementation of a charge exchange recombination
spectroscopy (ChERS) system on HSX. Her research focused on improving
the ChERS system and using it to measure plasma flow velocity, ion
temperature, and impurity ion density profiles. The radial electric
field, which can be deduced from flow and pressure gradient
measurements, was compared to the values predicted by neoclassical
- Alexis received her PhD in 2012 and currently employed by the Oak
Ridge National Laboratory Fusion Energy group and works at the General
Atomics Fusion Group/DIII-D Laboratory in San Diego, CA.
- Chris Clark
- Chris while at HSX was investigating impurity transport in the HSX
Stellarator. He led the development and construction of a laser
blow-off impurity injection system, which is currently being used to
introduce controlled quantities of impurities into HSX for analysis.
Data from this was analyzed using the STRAHL code modified for the
non-axisymmetric stellarator geometry.
- Chris did not complete his PhD but joined the ranks of Google and
currently works in Madison, WI.
- Bob Wilcox
- Bob studied the interaction of turbulence and flows in HSX and the
effects of quasi-symmetry on the determination of the radial electric
field in a stellarator. This was mainly done by using multi-tipped
Langmuir probes to measure the radial electric field, density and
potential fluctuations in the plasma edge, and then comparing these
measurements with neoclassical calculations.
- Bob received his PhD in 2014.
- Bob is currently employed by the Oak Ridge National Laboratory
Fusion Energy group and works at the General Atomics Fusion
Group/DIII-D Laboratory in San Diego, CA.
- Gavin Weir
- The primary area of Gavin's work centered on the design,
construction and implementation of the second ECH quasi-optical power
transmission system for delivering power from the second 28 GHz
gyrotron to HSX. The mirror is manually steerable to permit off-axis
power deposition control. His research included examination of the
heat propagation from modulated ECH heating, as compared to the
overall the overall thermal diffusivity - a measure of the profile
stiffness or resiliency, especially as this relates to the
axisymmetric tokamak devices.
- Gavin received his PhD in 2014
- Gavin is currently working at the Heliotron-J stellarator in Kyoto,
- Enrico Chlechowitz
- Enrico worked to extend the design of magnetic diagnostics on the
HSX stellarator. Optimization of the coil placements and field
components measured was carried out to guide the implementation of a
new array of in-vessel coil diagnostics used for equilibrium
reconstruction of the plasma density, pressure and current profiles.
- Enrico received his PhD in 2014 and is currently working with Roland
Berger Strategy Consultants in Germany.
- Jerahmie Radder
- Jerahmie's primary research area was in rf heating and the design
and fabrication of a quasi-optical launching system for the high-power
electron cyclotron resonance heating microwaves - 2 gyrotrons, 100-200
kilowatts each, for 50 to 75 milliseconds. His research concentrated
on measurement and modeling of power deposition and coupling to the
electrons under ECH, and predictions of a resultant non-Maxwellian
distribution in the electron population.
- Jerahmie is currently working in Minneapolis.