The Helimak as a realization of blob equations and for divertor concept improvement
Author: James C Wiley
Submitted: 2005-12-21 14:30:35
Co-authors: M. Kotschenreuther, P. M. Valanju, K. Gentle, D. Miracle, K. Lee, J. Felkl
Institute for Fusion Studies
1 University Station
Austin, TX 78712
The tokamak SOL and divertor region have recently been noted to be
an critical region in the extrapolation of current
tokamak designs to reactors due to the additional radiative fraction
that a reactor would have to shed from its core to protect the divertor.
Therefore understanding SOL energy balance is crucial to evaluating
novel divertor designs. We have extended the D'Ippolito[1-2]
model for SOL transport by including finite plasma transport along field lines.
We also include the thermal and electrical conductivity of the plasma which becomes
more import as the field line length increases and/or the temperature drops.
This allows a blob description of conduction limited regimes which are expected in
burning plasma SOL. Experimental results on the Helimak are beginning to
verify the blob model as a reasonable, simple two-dimensional model of the
key divertor physics. We show that numerical simulations of the blob
model agree well with recent Helimak results for relatively short
field line lengths Since the Helimak is an accessible realization of the blob theory, we
are examining the possibilities of modifying its topology to include
X-point physics and the investigation of a wetted liquid metal divertor region.
One of the questions with liquid metal walls is the rate at which heat can be
transferred out of the region with the liquid. The Helimak could easily be
modified to study heat flow from a magnetic field ending on a liquid metal
pool. We can use our validated code and the accessibility of Helimak
as a divertor simulator to study the effects of modifying the divertor magnetic geometry
(line lengths and plasma wetted area), and also adding liquid metal to the divertor plate.
1. S. I. Krasheninnikov, ``On scrape off layer plasma transport,'' Phys. Lett.
283, 368-370 (2001).
2. D. A. D'Ippolito, J. R. Myra, S. I. Krasheninnikov, ``Cross-field blob transport in tokamak scrape-off-layer plasmas,'' Phys. Plasmas 9, 222-233 (2002).
Place with abstracts by Kotscenreuther, Valanju, Pekker, Mahajan