The
HBT-EP tokamak is the fourth toroidal magnetic experiment constructed
within the
Columbia University Plasma Laboratory. HBT-EP was designed to demonstrate the feasibility of a high-beta
tokamak stabilized by a combination of a close-fitting conducting wall, plasma rotation,
and active feedback. The specific approach taken by HBT-EP was to investigate the
combined use of a close-fitting conducting wall and modular saddle coils for the purpose
of significantly extending the tokamak beta limit.
HBT-EP is a
unique experiment for the investigation of wall-stabilization because it is the only
tokamak device built with
adjustable walls. HBT-EP is also unique because the vacuum
chamber is made from several quartz cylindrical breaks. These allow fast penetration of
externally-applied magnetic perturbations. HBT-EP has been able to accelerate magnetic
islands to nearly sonic speeds, and the device has been used to access the Troyon normalized
beta limit with ohmic heating alone.
The specific approach taken in
HBT-EP incorporates:
A variety of fast-growing and slower resistive instabilities has been observed
in HBT-EP depending upon operating parameters. Installed diagnostics include
several arrays of Mirnov coils, cos (mq)
and sin (mq) Rogowski coils, 16-channel vertical soft x-ray detector
array, 32-channel tomographic diagnostic allowing reconstructions of Da
and soft-ray emission, 32-channel shell-mounted magnetic detectors for shell-eddy
current detection, multiple-point Thomson scattering, a microwave interferometer,
and movable magnetic probes. HBT-EP data is acquired with a 10-crate CAMAC
system using MIT's MDSPlus software, IDL, DEC Alpha workstations, and a dozen
other workstations.
Applied Physics and Math
