Exploring Experimental Isotope Scaling in Tokamak Transport
J. Weiland, T. Rafiq, and E. Schuster
65th Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)
Denver, CO, USA, October 30 – November 3, 2023
A problem that has not yet been resolved is the scaling of tokamak transport
with the ion mass [1]. Candidates for explaining this scaling are mainly
related to zonal flows [2]. Such flows are central to both the understanding
of the nonlinear Dimits shift and the H-mode barrier. We note that zonal
flows are sensitive to the fluid closure and also to the contribution to
the Reynolds stress by the pressure. We will study this effect in detail
using our most general electromagnetic description [3], including kinetic
ballooning modes as well as peeling modes and collisions. We will also
compare this with the effects of fast particles since we have recently
combined a theory for fast particles with our usual drift wave model [4].
In particular, it was found in [2] that the effects of collisions may be
needed for obtaining the experimental isotope scaling. We expect that
collisions may be needed in the outer parts of the H-mode barrier, where
our model is usually in the second stability region for MHD ballooning modes.
[1] J.W. Connor and H.R. Wilson, Plasma Phys. Control. Fusion 36, 719 (1994).
[2] S-I- Itoh and K. Itoh, Nuclear Fusion 56, 106028 (2016).
[3] J. Weiland, Stability and Transport in Magnetic Confinement Systems, Springer, New York (2012).
[4] J. Weiland, T. Rafiq and E. Shuster Phys. Plasmas 30, 042517 (2023).
*Supported by the US DE-SC0013977.