Influence of adiabatic response of passing energetic ions on high-frequency fishbone

【摘要】 Adiabatic response effects on high-frequency flshbone instability driven by passing energetic ions are studied. With flnite orbit width effects, the adiabatic contribution δW_hf is derived analytically for purely passing energetic ions. By approximating the adiabatic contribution to the flrst order of the reverse aspect ratio ε, we derive one of its analytic expressions, which is expected to be more accurate than that in a previous work（Graves J P 2004 Phys. Rev. Lett. 92185003）. For high-frequency flshbone instability, nonadiabatic response is usually dominant over adiabatic response, but under certain circumstances the latter plays an important role,comparable to the former. With a more generalized distribution function by introducing Gaussian-type factors representing their pitch and radial dependences and using a slowing-down equilibrium distribution for the energy of energetic ions, numerical analysis indicates that the adiabatic contribution is conducive to stabilization of the mode and causes a decrease in mode frequency. In addition, we flnd that the adiabatic contribution has a weak stabilizing effect on the flshbone instability when the flnite orbit width effect is taken into account. We further analyze the dependence of the adiabatic contribution on the characteristic parameters of the distribution function. When the neutral beam has either a larger deviation from the plasma axis or a larger radial proflle, the adiabatic contribution has a more evident effect on the flshbone instability.When the neutral beam has a relatively small critical energy, the adiabatic contribution has a greater effect on the mode instability.更多还原

【Abstract】 Adiabatic response effects on high-frequency flshbone instability driven by passing energetic ions are studied. With flnite orbit width effects, the adiabatic contribution δW_hf is derived analytically for purely passing energetic ions. By approximating the adiabatic contribution to the flrst order of the reverse aspect ratio ε, we derive one of its analytic expressions, which is expected to be more accurate than that in a previous work（Graves J P 2004 Phys. Rev. Lett. 92185003）. For high-frequency flshbone instability, nonadiabatic response is usually dominant over adiabatic response, but under certain circumstances the latter plays an important role,comparable to the former. With a more generalized distribution function by introducing Gaussian-type factors representing their pitch and radial dependences and using a slowing-down equilibrium distribution for the energy of energetic ions, numerical analysis indicates that the adiabatic contribution is conducive to stabilization of the mode and causes a decrease in mode frequency. In addition, we flnd that the adiabatic contribution has a weak stabilizing effect on the flshbone instability when the flnite orbit width effect is taken into account. We further analyze the dependence of the adiabatic contribution on the characteristic parameters of the distribution function. When the neutral beam has either a larger deviation from the plasma axis or a larger radial proflle, the adiabatic contribution has a more evident effect on the flshbone instability.When the neutral beam has a relatively small critical energy, the adiabatic contribution has a greater effect on the mode instability.更多还原