Abstract Details
Abstracts
Author: Xianzhu Tang
Requested Type: Poster
Submitted: 2019-02-22 17:13:55
Co-authors: Nathan Garland, Zehua Guo, Chris McDevitt, and Qi Tang
Contact Info:
Los Alamos National Laboratory
Theoretical Division, LANL
Los Alamos, NM 87545
USA
Abstract Text:
A desirable scenario for tokamak disruption mitigation is to inject enough deuterons into a disrupting plasma so the runaway avalanche can be completely avoided. Engineering constraints prefer the injection of high-Z impurities instead, and indeed, that is the method of choice on ITER. What is not settled yet
is the injection methods and the composition of the impurity
cocktail. Here we perform a runaway avalanche threshold analysis along with the collisional radiative modeling of impurity charge state distribution and radiative cooling power, to pin down the impurity content and composition that are required to avoid runaway avalanche, in an average sense that is constrained by the current ITER requirements on thermal quench and current quench time scales. Our finding gives a strong constraint on what is possible and more
importantly, what is not possible, with high-Z impurities, as currently planned for ITER.
In the case that runaway avalanche can not be completely avoided and a significant fraction of the plasma current is converted into runaway current, a workable scenario is to be able to limit the runaway energy so that material damage by the runaways is
manageable in a working reactor. The threshold energy would likely be in the MeV or sub-MeV as opposed to tens of MeV range. There are a couple of known ways to accomplish this. One possibility is high-Z impurities, which will be discussed in [1]. The other is external fast wave injection [2]. Here we will focus on the physics that underlies the options for optimization in the wave injection approach. Specifically we will present a simple physics model to show the options in designing the wave spectrum, not only for targeting particular energy cutoff as previously known [2], but also for minimizing the power requirement of the wave injection system.
Supported by DOE via Theory, TDS and SCREAM SciDACs.
[1] Garland et al. This conference. [2] Guo et al, PoP 25, 032504 (2018)
Comments:
