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 being the only tokamak device built with adjustable walls and having a vacuum chamber made with several quartz cylindrical breaks. These breaks allow fast penetration of externally-applied magnetic perturbations. HBT-EP has accelerated magnetic islands of nearly sonic speed and the device has been used to access the Troyon normalized beta limit with ohmic heating alone.
HBT-EP has ohmic parameters in the range given by:
- R = 0.92 m
- a = 0.15 m
- B = 0.35 T
- Te = 50 - 150 eV
- ne = 1 - 3 x 1019/m3
- βN = β/(Ip/aB) ≤ 2 % m.T/MA
- Ip ≤ 30 kA
Ph.D. and Eng.Sc.D. Programs on HBT-EP
Students join the HBT-EP group after after completing the M.S. program in applied physics, specializing in one applied physics field. Successful completion of an approved 30-point program of study is required in addition to successful completion of a written qualifying examination taken after two semesters of graduate study. An oral examination, taken within one year after the written qualifying examination, and a thesis proposal examination, taken within two years after the written qualifying examination, are required of all doctoral candidates.
The program builds a foundation in the science and application of plasma physics and features a specialty in the high-temperature plasma physics needed for controlled fusion energy. Besides a sound basic training in relevant areas of applied physics, students develop expertise in experimental, theoretical, and computational plasma physics. This instruction provides the background needed to conduct research in Columbia University’s Plasma Research Laboratory and in other national plasma research facilities. Since its inception in 1960, the program at Columbia has granted more than 110 doctoral degrees with many of our graduates playing leading roles in all phases of plasma physics, including, in particular, the worldwide program to develop controlled fusion energy.
Doctoral students typically join the HBT-EP group after passing qualifying exams at the end of their first year, but may take 2-3 research credits in the lab during one or both of their first two semesters. Early projects are usually introductory, involving work on analysis projects or assisting with the development, assembly, or installation of diagnostics.
After joining the group, a doctoral student may take on the development or operation of a particular diagnostic or another machine upgrade, or pursue a modeling or theory project, and may change research avenues until settling on a thesis project in agreement with their advisor. Experimental thesis projects are intensively hands-on, and students take on significant responsibility for the design and implementation of new systems with guidance from faculty and staff, as well as assisting with maintenance and repairs as needed. Most students learn to set up and operate all but the most sensitive of HBT-EP's systems and diagnostics.