AbstractNeutral particles in the LHD plasma periphery are investigated by three‐dimensional neutral particle transport simulation. The simulation predicts significant change of the density profile of neutral particles depending on magnetic configurations (radial position of the magnetic axis Rax ). The polarization resolved Hα spectra and the Hα intensity profile measured in the three different magnetic configurations are consistent with calculations by the simulation. It shows that the density of neutral hydrogen molecules in the inboard side of torus is relatively high in magnetic configurations (3.50m < Rax < 3.75m), which also indicates that enhancement of the neutral density by more than one order of magnitude is necessary for effective particle control in LHD plasmas. The simulation strongly suggests that installation of closed divertor components in the inboard side is reasonable. The simulation coupled with a one‐dimensional plasma fluid analysis on divertor legs proposes an optimized closed divertor configuration which can enhance the neural density in the inboard side of the torus. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)