Speaker
Description
CORC, STAR, and in general, conductors consisting of a set of helically wound conductors on a round core are of substantial interest for use in High Energy Physics accelerator magnets because of their high Bc2 and excellent transport properties in high fields. Their magnetization properties as well as their AC loss are also of interest, because they can cause particle beam defocusing and excess cryogen losses, respectively. In this work we use a combination of finite element and analytical modelling to calculate three important loss components, (i) hysteretic, (ii) eddy current, and (iii) coupling current losses. We chose to treat the case of fields well above penetration for simplicity, and also we take the case of low to modest ramp rates, both because it is the regime of interest for particle accelerators, but also because it allows us to treat these three components as non-interacting, at least for fields well above penetration. The hysteretic losses of tapes is seen to agree with (2/)* the straight tape in a perpendicular field if the cable pitch is large enough, and eddy currents with non-helical eddy current tape loss by (2/)2. The additional losses due to coupling currents can be estimated by treating the losses as a summation of tape pairs with inter-tape coupling currents. FEM calculations are compared to analytic models for these pairs over a range of sample lengths and dB/dt values before summing to give a total coupling loss. In this way we make an estimate of total CORC Magnetization and losses using a simple and fast model.
