Simulation of multi-pulse coaxial helicity injection in the Sustained Spheromak Physics Experiment
- Univ. of Maryland, Baltimore County, MD (United States). Dept. of Mechanical Engineering; Univ. of Washington, Seattle, WA (United States). Dept. of Aeronautics and Astronautics
- Univ. of Maryland, Baltimore County, MD (United States). Dept. of Mechanical Engineering
- Woodruff Scientific, Inc., Seattle, WA (United States)
Nonlinear, numerical computation with the NIMROD code is used to explore magnetic self-organization during multi-pulse coaxial helicity injection in the Sustained Spheromak Physics eXperiment. We describe multiple distinct phases of spheromak evolution, starting from vacuum magnetic fields and the formation of the initial magnetic flux bubble through multiple refluxing pulses and the eventual onset of the column mode instability. Experimental and computational magnetic diagnostics agree on the onset of the column mode instability, which first occurs during the second refluxing pulse of the simulated discharge. Our computations also reproduce the injector voltage traces, despite only specifying the injector current and not explicitly modeling the external capacitor bank circuit. Furthermore, the computations demonstrate that global magnetic evolution is fairly robust to different transport models and, therefore, that a single fluid-temperature model is sufficient for a broader, qualitative assessment of spheromak performance. Although discharges with similar traces of normalized injector current produce similar global spheromak evolution, details of the current distribution during the column mode instability impact the relative degree of poloidal flux amplification and magnetic helicity content.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Grant/Contract Number:
- AC52-07NA27344; AC02-05CH11231
- OSTI ID:
- 1498097
- Journal Information:
- Physics of Plasmas, Vol. 25, Issue 3; ISSN 1070-664X
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Numerical study and optimization of the formation and sustainment of a coaxial helicity injection spheromak
|
journal | November 2018 |
Similar Records
Sustained spheromak coaxial gun operation in the presence of an n=1 magnetic distortion
Sustained spheromak physics experiment