The CHS-qa is a quasi-axial symmetric device, and its design work has been continued. In its design process, the geometry of outermost magnetic surface, which characterizes the optimum magnetic configuration, is determined at the beginning, and after that, the coil system which produces this magnetic surface is designed. The discrete modular toroidal coils are used for the coil system. Since the total number of coils is restricted, the bumpy ripple arises, which is not considered in the optimization process of outermost magnetic surface. The bumpy ripple deteriorates the neoclassical transport in 1/ν regime. This effect of bumpy ripple on the 1/ν neoclassical transport is not easy to calculate analytically for CHS-qa, because those shapes of modular toroidal coils are 3-dimenstional and structure of ripple is complicated. Therefore a numerical calculation is employed. For this numerical calculation, NEO-code [1] is used which can include effects of all ripples of magnetic field in the evaluation of 1/ν neoclassical transport. The bumpy ripple is important for the high-energy particle loss as well as neoclassical transport. The dependence of bumpy ripple on the high-energy particle loss is also investigated by drift orbit calculation.
Other issue related to coil design is the error of magnetic field that is caused by the error of coil location and slant. The modular coils are made separately in a factory, after that, all coils are assembled to the device. In this process of coil assembling, the error in position of coils may occur. In order to know the permissible error level for the coil position and slant, the effect of this error on the transport is examined.

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