Current HSX Graduate Students
- Jerahmie Radder
- Area - rf heating and 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 is concentrating on measurement and modeling
of power deposition and coupling to ple electrons under ECH, and
predictions of a resultant non-Maxwellian distribution in the electron
- 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
- Gavin Weir
- Area - 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 to be manually steerable to
permit off-axis power deposition control. His research includes
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
- 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
- Bob Wilcox
- Bob is studying 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 is 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.
- Enrico Chlechowitz
- Enrico is working to extend the design of magnetic diagnostics on the
HSX stellarator. Optimization of the coil placements and field
components measured has been carried out to guide the implementation of
a new array of in-vessel coil diagnostics which will be used for
equilibrium reconstruction of the plasma density, pressure and current
- 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 determination.
- Ali Abdou
- 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
- 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 density.
- John received his Ph.D. in Spring of 2007 and currently works at Oak
Ridge National Laboratory under a prestigious Wigner Fellowship.
- 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
- 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 scattering
- 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.