5. Conclusions

Plasma detachment from divertor targets is an important and very interesting phenomenon in fusion devices including helical systems and tokamaks. On the one hand, it can lead to the deterioration of the plasma performance and even to the total collapse of the discharge. On the other hand, detachment, if it is controlled and Experimental Studies of and Theoretical Models for Detachment in Helical Fusion Devices DOI: http://dx.doi.org/10.5772/intechopen.87130

stable can be useful for the reduction of the heat power losses to the target plates and even may lead to peaking of the pressure profiles in the plasma core that manifests in a confinement improvement. Resonant magnetic perturbations providing a broad enough magnetic island close to the separatrix has proven to be an effective method to control detachment in LHD.

Often at the onset of the detachment, large nonlinear oscillations of relatively low frequency can be observed in different plasma parameters, such as radiated power and ion saturation current to the target plates. Two models of such selfsustained oscillations are proposed. The first one is relevant to the radial detachment in LHD with divertor legs of low plasma density and transparent for neutrals. The second model offers an explanation for phenomena in tokamaks observed at the transition from strong recycling to plasma detachment at divertor targets.
