Abstract
Current profile reconstructions are obtained for high current ( I p ≃ 550 kA) post-disruption runaway electron (RE) plateau plasmas in DIII-D. Two novel methods of measuring the RE current profile in high-current RE plateaus are introduced and compared: localization of the q = 2 rational surface using visible synchrotron emission (SE) imaging and the measurement of the polarization angle of line-integrated Ar-II line emission. The two methods are found to be consistent with each other within the data uncertainties. Different simulations of the RE current profile are compared with the measurements: the toroidal fluid RE model is found to best fit the data, within the measurement uncertainties. In addition to introducing two novel methods to measure the RE current profile and validating present simulation capabilities, this work demonstrates that instabilities can grow at q = 2 and q = 1 surfaces without necessarily causing a RE final loss instability. Numerical simulations are also presented to elucidate the role of these instabilities on synchrotron emission.
| Original language | English |
|---|---|
| Article number | 076039 |
| Journal | Nuclear Fusion |
| Volume | 64 |
| Issue number | 7 |
| DOIs | |
| State | Published - Jul 2024 |
Funding
This work was supported by the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences, sponsored by the DIII-D National Fusion Facility, under the Grants Nos. DE-FG02-07ER54917 and DE-FC02-04ER54698, and by the Oak Ridge National Laboratory, operated by UT-Battelle, LLC, for the U.S. Department of Energy under Contract DE-AC05-00OR22725. This research also used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science user Facility operated under Contract No. DE-44 AC02-05CH11231.
Keywords
- MHD instabilities
- current profile
- line polarization
- runaway electrons
- synchrotron emission