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fvolpe_columbiastellarators_talk.pdf2014-08-12 15:25:54Francesco Volpe
fvolpe_columbiastellarators_abstract.pdf2014-08-12 15:16:24Francesco Volpe

Stellarator Experiments at Columbia University

Author: Francesco A. Volpe
Requested Type: Consider for Invited
Submitted: 2014-06-05 12:59:03

Co-authors: C. Caliri, A.W. Clark, M. Doumet, K.C. Hammond, B.Y. Israeli, Y. Kornbluth, S.A. Lazerson, D.A. Spong, R. Sweeney

Contact Info:
Columbia University
204 S.W. Mudd, Mail Code: 4701
New York, NY   10027
USA

Abstract Text:
The Columbia Non-neutral Torus (CNT) has been modified for the study of quasi-neutral plasmas formed and heated by Electron Cyclotron (EC) waves at 2.45GHz, 1 kW. Here we present fast-camera and Langmuir probe measurements and describe the undergoing installation of additional diagnostics and upgrade to 10 kW heating, as well as plans for even higher power and/or different heating schemes, taking advantage for instance of an existing 1-3 MHz, 4MW source. CNT is the stellarator with the lowest aspect ratio in the world, high fraction of trapped particles and large vessel with wide diagnostic access and camera views. Additionally, its low field and suitability for Electron Bernstein Wave heating at high density might lead to high beta. Research ideas will be discussed in the areas of wave physics, high beta magnetohydrodynamics, error-fields, transport and stellarator scaling of the divertor wetted area. The recently completed table-top circular coil (CIRCUS) tokamak-torsatron hybrid will also be presented. Its six “toroidal field” coils are planar as in a tokamak, but they are tilted and interlinked with each other, and expected to generate rotational transform when combined with an induced or driven plasma current Ip. The device can be operated at lower Ip than an equivalent tokamak with non-tilted coils and is characterized by a smaller effective ripple. Comparisons between calculations and field-line mapping measurements for various coil tilts and positions will confirm whether this relatively simple concept can generate the expected rotational transform. Finally, modeling suggests that a small EC-heated classical stellarator might significantly improve the production-rate and charge-state of ions in EC-resonant ion sources (ECRIS) over their conventional magnetic-mirror and hexapole design. We discuss how ions would be extracted from such a source and injected in accelerators for nuclear and particle physics studies, as well as for hadron-therapy.

Characterization: 1.0

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Workshop on Exploratory Topics in Plasma and Fusion Research (EPR) and US-Japan Compact Torus (CT) Workshop
August 5-8, 2014
Madison, Wisconsin

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