The paper presents the first reported observation of high frequency Alfvn eigenmode excitation on the ASDEX Upgrade tokamak. The mode is driven in a novel way using radio frequency (RF) wave acceleration of either beam-injected deuterium ions or thermal He-3 minority ions in a three-ion heating scenario. In the case of beam ion acceleration, the instability only appears during deuteron acceleration at the third beam ion cyclotron harmonic (wave frequency ω = 3Ω_D where Ω_D is the deuterium cyclotron frequency), as the mode is not detected during the more commonly used second harmonic/minority heating scenario or in the absence of beam-injected ions. The mode frequency is around 0.6–0.7Ω_D, where Ω_D is evaluated in the low-field side plasma edge, and tracks the magnetic field B and the edge plasma electron density n_e via the Alfvnic relation ω ∼ B n_e^−1/2. The mode does not appear as a single frequency wave but as a bundle of closely spaced (in frequency) sub-modes. When the parallel beam ion velocity component is increased, the sub-mode frequency spacing is observed to decrease, possibly due to a change in the eigenmode structure. Under certain conditions, typically in discharges with a relatively low plasma current, I_P < 0.7 MA, the mode appears to be driven directly by sub-Alfvnic deuterium beam ions. Absolute measurements of the mode amplitude show that at least 1% of the beam-injected power is transferred non-collisionally to the instability. While this is too low for practical alpha-channeling applications, discharges are planned with the aim of increasing the level of power transferred non-collisionally between fast ions and the instability.

本文介绍了在ASDEX升级托卡马克上首次出现的高频Alfvn本征模激发的观察结果。在三离子加热方案中，使用射束注入的氘离子或热He-3少数离子的射频（RF）波加速，以新颖的方式驱动该模式。在束离子加速的情况下，不稳定性仅在第三束离子氘核加速回旋加速器谐波（波频率中出现ω =3Ω _d其中Ω _d为在更常用的是未检测到的模式是氘回旋频率），二次谐波/少数加热方案或没有离子注入离子的情况。模式频率大约0.6-0.7Ω _d，其中Ω _d在低场侧等离子体边缘被评估，并跟踪磁场B和边缘等离子体电子密度Ñ _Ë经由Alfvnic关系ω〜B n的_ë ^-1/2。该模式不显示为单个频率波，而是显示为一束紧密间隔的（在频率上）子模式。当平行束离子速度分量增加时，观察到子模频率间隔减小，这可能是由于本征模结构的变化引起的。在某些条件下，典型地在具有相对低的等离子体电流，放电我_P<0.7 MA，该模式似乎直接由亚Alfvnic氘束离子驱动。模态振幅的绝对测量结果表明，至少有1％的光束注入功率会非碰撞地传递给不稳定性。尽管对于实际的Alpha通道应用来说这太低了，但计划进行放电是为了增加快速离子之间的非碰撞传递功率和不稳定性。