Wave Excitation in Magnetically Confined Plasmas with an Anisotropic Velocity Distribution

In magnetically confined plasmas, fluctuations in the ion cyclotron range of frequency (ICRF) will be driven by the presence of non-thermal ion energy distributions. In a typical discharge in the GAMMA 10 tandem mirror, Alfvén-ion-cyclotron (AIC) modes are spontaneously excited due to strong temperature anisotropy. On the other hand, in fusion-oriented devices with a toroidal configuration, neutral beam (NB) injection is commonly used to create high performance plasmas. The resultant high-energy ions are trapped in local mirrors and will form velocity distributions with strong anisotropy. Especially in burning plasma experiments on JET and TFTR, fusion-product (FP) ions form non-thermal ion energy distributions in the bulk plasma and ion cyclotron emission (ICE) has been observed. The main purpose of this work is to study the relation between AIC-modes and ICEs in magnetically confined plasmas with non-thermal energy distributions. Recently, fluctuation measurements made by using ICRF antennas as pickup loops on JT-60U have been started. When the deuterium-NBs are injected into deuterium bulk plasma, magnetic fluctuations due to injected beams and FP ions are detected. Wave excitation near the ion cyclotron frequency and its higher harmonics is studied experimentally in plasmas with non-thermal ion energy distributions.