EX/P4-24 Advanced Divertor Scenario in the Large Helical Device

Neutral particle behavior in the Large Helical Device heliotron has been investigated to conduct the effective particle control using the intrinsic helical divertor. The torus in–out asymmetry was observed in the neutral pressure distribution, and the degree of the asymmetry depends on the divertor particle flux distribution, and thus, on the operational magnetic configuration. This asymmetry was well reproduced by the fully threedimensional neutral transport code, EIRENE. Degradation of the plasma confinement with increasing of the neutral pressure was observed, and that suggests the effective particle control is necessary for the sustaining of long discharge with high performance plasma and the further improvement of the confinement. The modification of the open helical divertor to the closed one is planned for the particle control using helical divertor. It has been investigated using EIRENE code. Results of the calculation show that proper rearrangement of divertor plates and additional components, such as dome structure make the neutral particles to be compressed well in the divertor region, and effective divertor pumping to be possible. Based on the simulation and experimental results, design and installation of closed helical divertor is programmed in the Large Helical Device in the near future.