The MEDUSA (=Madison EDUcational Small Aspect-ratio) Tokamak is a low-aspect ratio tokamak built and designed almost entirely by students, primarily undergraduates, at the University of Wisconsin Madison Nuclear Engineering & Engineering Physics department under the guidance of Dr. Raymond Fonck. Its purpose is to probe low aspect ratio tokamak performance for fusion energy research and plasma physics applications. A tokamak like MEDUSA is a magnetic bottle designed to hold plasmas at the very high temperatures required for fusion energy. For those who haven't had previous experience with fusion energy, the lab a General Atomics has put together a slide show that explains the basics as well as a page of term definitions, and another page here gives you an introduction to what a Tokamak is.
Where We Are Now:
MEDUSA is part of a generation of machines designed to address advanced Tokamak design issues that may achieve these goals.
- Some time in the 21st Century, we will need a new primary energy source, despite gains in efficiency:
- Fossil fuels are running out and are polluting the atmosphere.
- Hydro power capacity is being lost as rivers must be freed to protect fish and other water resources.
- Solar and wind systems seem unable to meet society's energy demand due to uneven supply and low power density.
- Fission produces long-lived radioactive waste products, and will eventually be depleted.
- Magnetic Confinement Fusion may provide an alternative, but current-technology reactors would be:
- We need a fusion concept which is:
With an aspect ratio (major/minor radius) of 1.5, MEDUSA is one of approximately 6 low aspect ratio Tokamaks in operation. The low aspect-ratio concept has a number of advantages that make it a promising approach to advanced tokamak design, which MEDUSA is designed to probe.
- Physical Specifications:
Cross-sectional drawing of MEDUSA
- Major Radius: 10-24 cm
- Minor Radius: 6-9 cm
- Design Aspect Ratio: 1.5 (low aspect ratio)
- Vacuum Vessel: Glass w/ steel surfaced alumina core, rectangular cross-section
- Limiters: Stainless Steel
- Installed Capacitor Storage: 90kJ
- More information and lab pictures here.
- Mirnov and Rogowski Coils, Flux Loops (Magnetic diagnostics)
- Triple Langmuir probe (Temperature and Density)
- Filter Spectroscope (Temperature)
- High Speed Camera (Plasma Shape and Position)
- Internal Magnetic Probe Array
- Machine Performance:
False color image of MEDUSA plasma
- Maximum Toroidal Field: 0.45 Tesla
- Maximum Plasma Current (Projected): 40-60 kA
- Maximum Plasma Current (Attained): 40.0 kA
- Maximum Pulse Length(Projected): 5ms
- Maximum Ohmic Flux Swing: 20mV-S
- More information on MEDUSA plasmas is here.
- Research Concentrations
- Plasma stability at low aspect ratio.
- High plasma current and very high (~1.7MA/m^2) current density operation.
- Plasma startup, sustainment, and flux consumption at low aspect-ratio.
- More detailed data and information here.
- The Next Step: Pegasus
Greg Garstka / 6-14-96 /