  A neoclassically optimized compact stellarator with simple coils has been
designed. The magnetic field of the new stellarator is generated by only four
planar coils including two interlocking coils of elliptical shape and two
circular poloidal field coils. The interlocking coil topology is the same as
that of the Columbia Non-neutral Torus (CNT). The new configuration was
obtained by minimizing the effective helical ripple directly via the shape of
the two interlocking coils. The optimized compact stellarator has very low
effective ripple in the plasma core implying excellent neoclassical
confinement. This is confirmed by the results of the drift-kinetic code SFINCS
showing that the particle diffusion coefficient of the new configuration is one
order of magnitude lower than CNT's.
