Pegasus in operation

Our groups within the Department of Engineering Physics carry out experimental magnetic fusion research at facilities on the UW-Madison campus and at international-class facilities around the world.  The breadth of activities spans spherical torus, tokamak, and stellarator devices; core turbulence, edge stability, and the plasma-material interface; non-inductive startup and current drive; and innovative diagnostic and radio-frequency heating techniques.

For information about undergraduate and graduate research opportunities, please contact the faculty and staff listed below for each project.

Non-inductive startup on Pegasus-III

The Pegasus-III research program examines the leading startup techniques in a single experiment. The candidate techniques include DC helicity injection, including Local Helicity Injection, Sustained Coaxial Helicity Injection (S-CHI), and Transient Coaxial Helicity Injection (T-CHI); radio-frequency (RF) electron heating and possibly current drive with electron Bernstein waves; poloidal field induction; and in the future neutral beam current drive as needed.  The overarching goal is to demonstrate routine non-inductive plasma startup that promises scalability to NSTX-U and beyond. (R. Fonck, S. Diem, M. Bongard, J. Goetz, M. Nornberg, J. Reusch, A. Sontag) Pegasus-III website »

2D Beam Emission Spectroscopy on DIII-D, NSTX-U, and HL-2A

We develop and operate 2D Beam Emission Spectroscopy (BES) diagnostics at DIII-D, NSTX-U, and HL-2A to investigate ion-gyro-scale turbulence and instabilities. 2D BES measurements are versatile with applications to turbulence (ITG, TEM, KBM turbulence), instabilities (edge-localized modes, Alfven instabilities), and flow fields. BES measurements have made key scientific contributions to the understanding of the LH transition, zonal flows, and the turbulent Reynolds stress. (G. McKee, R. Fonck, D. Smith, Z. Yan) Turbulence diagnostic group website »

3D plasma boundaries and the plasma-material interface

Across multiple projects and facilities, we seek to understand the self-consistent feedback loop between plasma-wall interaction, edge and core plasma transport and stability of 3D configurations. Plasma edge physics and plasma surface interactions in the presence of 3D plasma boundaries are relevant to tokamak devices with applied resonant magnetic field perturbations and inherently 3D stellarators. (O. Schmitz, H. Frerichs) 3D PSI website »

3D impurity transport in HSX and W7-X

This project investigates turbulent impurity transport on the Helically Symmetric eXperiment (HSX) in Madison, WI and at the Wendelstein 7-X (W7-X) stellarator in Greifswald, Germany. Existing laser ablation systems on both experiments will be equipped with optimized and calibrated glass targets that will allow active impurity injections with a well-controlled amount of particles. The spectroscopy measurements will provide absolutely calibrated impurity densities with excellent spatial resolution and will resolve the inwards movement of impurities toward the plasma core following the injections. (B. Geiger)

Non-inductive current drive with helicon waves at DIII-D

We tackle the cutting edge topics on large-scale facilities and address important basic plasma science questions such as generation of high-density plasmas with helicon waves. (O. Schmitz, H. Frerichs, E. Hinson) 3D PSI website »

Spatial heterodyne spectroscopy for electric and magnetic field fluctuation measurements

Spatial heterodyne spectroscopy (SHS) involves high-speed measurements of the spectral linewidth of light emitted from an energetic diagnostic neutral beam. The measurement is spatially localized by the  cross-beam measurement geometry of beam spectroscopy techniques. Changes in the local magnetic field change the linewidth of the emission line manifold, but generally at different frequencies than the electric fluctuations.  These rapid spectral linewidth measurements, with optical sightlines in the readily-accessible plasma midplane, provide measurements of specific vector components of the perturbed electric or magnetic fields. (B. Geiger, R. Fonck, G. McKee, M.G. Burke)

ELM control with non-axisymmetric 3D fields

In this multi-institution project, we pursue the prediction and optimization of divertor heat flux profiles in ELM suppressed scenarios. (H. Frerichs, O. Schmitz) 3D PSI website »

Edge ML for real-time data reduction with Beam Emission Spectroscopy

This multi-institution project applies machine learning techniques to multiple facets of the plasma control system at DIII-D. In the context of Beam Emission Spectroscopy (BES), we are developing “edge ML” algorithms for real-time data reduction and featurization of BES data on high-throughput FPGA devices. The resulting data streams are then available to the central plasma control system for real-time prediction and control. (D. Smith, Z. Yan, G. McKee) Turbulence diagnostic group website »

Multi-spectral imaging and gas puff imaging diagnostic systems at the TCV tokamak

We develop and operate two key diagnostic system to understand boundary, scrape-off layer, and divertor physics issues. The Multi-Spectral Imaging (MSI) system probes plasma dynamics in the divertor region under the wide range of configurations.  We also develop innovated nozzles for the Gas Puff Imaging diagnostic to study the response of the main plasma boundary to variation of the plasma triangularity and divertor dynamics. (O. Schmitz) 3D PSI website »

Formation and tuning of the plasma column in the AWAKE plasma wakefield accelerator at CERN

The focus of this research project is on the physics of generating very uniform plasmas for future particle accelerator applications. This project aims to improve the understanding of how a plasma column can be formed and tuned for the requirements in the AWAKE accelerator application. The goal of this research is to resolve the helicon transition and understand the ionization dynamics during the transition and shortly afterwards. (O. Schmitz)