Year: 2024
Type: article
Abstract: The impurity effects on kinetic ballooning modes (KBMs) in high q regions of tokamak plasmas are numerically investigated, using a full gyrokinetic description for main and impurity ions. The findings indicate that the critical plasma pressure ratio β c for KBM is significantly lower (higher) than the first (second) stable threshold β MHD predicted by MHD theory. The KBM exhibits stronger extended instabilities for low q , while the instability region of KBM becomes significantly narrow for high q , resulting in a more concentrated instability window (localized in narrow medium- β region). In addition, the contributions from electromagnetic effect and Shafranov shift are identified in detail, i.e. the electromagnetic destabilizing effect is suppressed by the Shafranov shift, and strong stabilizing effect of Shafranov shift for high β e or α on KBM is pronounced. The impurity ions with negative gradient ratio L e z have stabilizing (destabilizing) effects on KBMs for high (low) q . Such distinct behaviors are demonstrated to be associated with the used parameters close to the second and first unstable α region, i.e. the instability reduces and enhances with the increase of α , respectively. Significantly, the presence of impurities, regardless of the peaking directions of their density profiles, serves to stabilize KBMs and reduce the window of extended instability for high q region, which is in significant contrast with the results for low q region. Furthermore, high concentration, steep negative gradient ratio L ez , and high mass numbers of impurity ions as well as large temperature gradient η i and η e
Source: Nuclear Fusion
Authors: J. Li, J.Q. Dong, J.Y. Liu, Z.X. Wang, X.R. Zhang, R. He
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,470
OpenAlex ID: W4404797528