The transport of particles and energy into the scrape-off layer (SOL) region at the outboard midplane of medium-sized tokamaks, operating in low confinement mode, is investigated by applying the first-principle HESEL (hot edge-sol-electrostatic) model. HESEL is a four-field drift-fluid model including finite electron and ion temperature effects, drift wave dynamics on closed field lines, and sheath dynamics on open field lines. Particles and energy are mainly transported by intermittent blobs. Therefore, blobs have a significant influence on the corresponding profiles. The formation of a 'shoulder' in the SOL density profile can be obtained by increasing the collisionality or connection length, thus decreasing the efficiency of the SOL's ability to remove plasma. As the ion pressure has a larger perpendicular but smaller parallel dissipation rate compared to the electron pressure, ion energy is transported far into the SOL. This implies that the ion temperature in the SOL exceeds the electron temperature bya factor of2-4 andsignificantly broadens the power deposition profile.

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In this paper we investigate parametric decay of an electromagnetic pump wave into two electrostatic daughter waves, particularly an X-mode pump wave decaying into a warm upper hybrid wave (a limit of an electron Bernstein wave) and a warm lower hybrid wave. We describe the general theory of the above parametric decay instability (PDI), unifying earlier treatments, and show that it may occur in underdense and weakly overdense plasmas. The PDI theory is used to explain the anomalous sidebands observed in collective Thomson scattering (CTS) spectra at the ASDEX Upgrade tokamak. The theory may also account for similar observations during CTS experiments in stellarators, as well as in some 1st harmonic electron cyclotron resonance and OX -B heating experiments.

We present observations of microwave diagnostics damage in three discharges employing third-harmonic X-mode electron cylcotron resonance heating (ECRH) at the ASDEX Upgrade tokamak. In all cases, the diagnostics damage is explainable in terms of a parametric decay instability (PDI), where an X-mode ECRH wave decays to two trapped upper hybrid (UH) waves near half the ECRH frequency, followed by secondary instabilities, which generate strong microwave signals near multiples of half the ECRH frequency that cause the damage. Trapping of the UH waves near half the ECRH frequency is necessary to reduce the ECRH power required for exciting the PDIs to a level attainable at ASDEX Upgrade, and may occur when the second-harmonic UH resonance of the ECRH waves is present in a region of non-monotonic electron density, e.g. near the O-point of a magnetohydrodynamic mode or the plasma center. The diagnostics damage in the three discharges may be attributed to PDIs occurring near the O-point of a rotating mode, near the plasma center, and near the O-point of a locked mode, respectively. In the rotating mode case, the strong signals are shown to be quasi-periodic, with spikes occurring when the O-point of the mode passes through an ECRH beam, as expected. In the locked mode case, Thomson scattering profiles demonstrate the possibility of the primary PDI occurring based on experimental data for the first time under fusion-relevant conditions. Applying the framework used for ASDEX Upgrade to the X-mode ECRH scenarios planned for the early operation phase of ITER, the PDIs are found to be likely in connection with 170 GHz ECRH of half field scenarios and 104 GHz (or 110 GHz) ECRH of one third field scenarios. Finally, several strategies for mitigating diagnostics damage are proposed.