Innovative Non-Resonant Divertors Applied to Compact Toroidal Hybrid (CTH)

Non-resonant divertors separate the confined plasma from surrounding structures with the resulting boundary region comprised of cantori and/or stochastic regions, but without the presence of large islands. In contrast, island divertor configurations make use of low order rational surfaces with large islands mediating the confined plasma and the wall. These islands are highly sensitive to the value and shear of the rotational transform which can be affected by the evolution of the plasma equilibrium. Compact Toroidal Hybrid (CTH) can serve as a test-bed for the non-resonant divertor solution for divertor optimization. The currents in the field coil and ohmic current drive systems of CTH are controlled to alter the rotational transform between 0.3 < ι < 0.75. Utilizing the FLARE field-line following code, we calculate strike point locations for the exiting plasma for multiple ohmic current values. These calculations provide possible locations for divertor plates that will be built in the experiment to test non-resonant divertor resiliencies. These same techniques can be applied to other machines including ones that use the island divertor in the standard operation, like W7-X.