Speaker
Alkesh Punjabi
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1014.pdf
Effects of magnetic perturbations on axisymmetric divertors
Alkesh Punjabi1, Allen Boozer2
1
Hampton University, Hampton, VA 23668, USA
2
Columbia University, New York, NY 10227, USA
The behavior of the magnetic turnstiles that depart plasma from axisymmetry to strongly
perturbed is studied. An analytic model is derived in which the width and nature of the
intersection of points of magnetic flux tubes can be studied. This exact model is based on the
Boozer-Rechester two wire model [A. H. Boozer and A. B. Rechester, Phys. Fluids 21, 682
(1978)]. Boozer and Rechester represented the magnetic field using the complete elliptic
integrals and the Jacobi elliptic functions, but they did not place the equations in terms of an
explicit magnetic field line Hamiltonian. In our model this is done and the magnetic field lines
are modified by the addition of a fixed small radial spiraling velocity. The lines eventually
cross the outermost confining magnetic surface and form flux tubes that strike the surrounding
walls. The width and nature of the intersection of points of these flux tubes are studied in the
limit as the spiraling velocity vanishes. This is done for both an axisymmetric divertor and for
an axisymmetric divertor subjected to a quadrupole perturbation that has an orientation that
rotates with the toroidal angle. The flux escaping through the turnstiles must exactly equal the
returning flux. The scaling of the loss time and the size of intersection with the spiraling
velocity are studied. General universal scaling laws characterizing the effects of perturbation
on the axisymmetric divertors are sought. This work is supported by the US DOE grants DE-
FG02-01ER54624 and DE-FG02-04ER54793 to Hampton University and DE-FG02-
95ER54333 to Columbia University. This research used resources of the NERSC, supported
by the Office of Science, US DOE, under Contract No. DE-AC02-05CH11231.
