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icc2007.pdf2007-02-20 20:29:46Adil Hassam

Progress on the Maryland Centrifugal Experiment

Author: Adil Hassam
Requested Type: Consider for Invited
Submitted: 2006-12-19 13:10:56

Co-authors: R. F. Ellis, S-H Choi, R. Clary, R. Elton, P. Guzdar, R. Lunsford, S. W. Ng, I. Shamim, C. Teodorescu, I. Uzunkay

Contact Info:
univ of md
college park, md   20742

Abstract Text:
Progress in the understanding of the physics and operation of the Maryland Centrifugal Experiment
(MCX) in the last year is reported. The MCX continues to routinely obtain supersonic rotation at
Mach numbers ranging from 2-3. Long steady discharges are obtained, steady over 1000's of
interchange instability growth times. Parabolic type radial profiles of angular velocity
omega(psi) have been obtained from Carbon spectroscopy, clearly demonstrating shears in the plasma
rotation that exceed the critical velocity for velocity shear stabilization by up to factors of 5.
Over the last year, progress has been made on several fronts: (1) with insulator optimization, the
duration of the previously reported high-rotation (HR) mode has been extended and a bifurcation
theory of the two modes of operation has been developed. (2) The scaling of maximum rotation
speed with applied voltage and, separately, B, has been investigated. The scaling shows a rollover
of rotation speed with higher voltage. Two possibilities to account for this are a speed limit
from an ionization instability at the insulator (Lehnert et al), and an MHD rotation beta limit.
(3) Measurement of the omega(psi) profiles versus axial distance show departure from ideal low-beta
MHD; higher beta is being examined. (4) Scaling of the momentum confinement time with changing
plasma size shows an a^2 dependence. Future plans for MCX include (a) a completely new insulator
designed to minimize surface breakdowns and possibly mitigate speed limits; (b) a plasmoid will
be fired from a gun off-axis to impart momentum to the plasma (in collaboration with Hyper-V Tech);
(c) addition of an extra coil to increase the max magnetic field at the mirrors by 30%.

Characterization: A1


University of Maryland

Innovative Confinement Concepts Workshop
February 12-14, 2007
College Park, Maryland

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