Placing an l=1 continuous helical coil with a pitch modulation in an axisymmetric toroidal magnetic field, a helical axis configuration was obtained with characteristics similar to the Helias configuration for Wendelstein 7-X (W7-X). In the four pitch case, a device with an aspect ratio of 4-5 and good accessibility becomes possible, although a very weak magnetic hill exists. In a particular finite β magnetohydrodynamic (MHD) equilibrium, the magnetic well appears in the whole region for a central β value of β(0) ~ 1%. About a quarter of the particles at half radius are lost at β = 0; however, both the radial electric field and the finite β effect improve the particle orbit confinement significantly. The possibility of an open divertor is shown
Effect of helical coils on the magnetic field and the stability ofa compact toroidal plasma