University of Wisconsin-Madison Physical Sciences Lab

HSX Helically Symmetric Toroidal Experiment

[Photo of HSX August 1999]

PSL has been heavily involved in the HSX project, which is a new concept in fusion reactors that combines the best features of stellarator and tokamak plasma technology. The key to HSX is its unique helical toroidal shape. The vacuum chamber, which looks like a warped donut, is surrounded by twisted coils of copper. When an electric current is run through these complicated coils, a simple magnetic field is produced which confines the plasma inside the vacuum chamber. Because HSX is essentially a stellarator, it does not require a strong current in the plasma. However, its unique shape produces the high-quality magnetic field that is the advantage of tokamaks.

PSL has been involved since 1993, especially in the design and integration of the device. PSL mechanical engineer Bill Mason developed the complicated system of supports for the vacuum chamber, coils, cooling systems, and the electrical and diagnostic systems. This system has to allow access to all parts of the device, but still be able to withstand the large magnetic forces produced. PSL also produced the support structure and participated in its installation.

PSL helped with the mapping of the magnetic field and in the development of systems for measuring plasma properties.

We were pleased to learn that the HSX has demonstrated the projected reduction in plasma energy loss, described in an article in the UW-Madison College of Engineering‘s Perspective Spring 2007 issue. The article refers to Physical Review Letters 98, 085002 (2007).