Possibility of strong anomalous absorption of microwaves in electron cyclotron resonance heating experiments in fusion devices

The effect of strong anomalous absorption (up to three-quarters of the pump power) of microwaves in electron cyclotron resonance heating (ECRH) experiments in toroidal devices is predicted. It originates from the low-power-threshold two-plasmon parametric decay instability, for which the only effective saturation mechanism is provided by the pump wave depletion. This makes the power deposition profile different from that predicted by the linear theory and provides an alternative interpretation for its evident broadening observed on ECRH in toroidal devices. (letter)