  A backward computation method has been developed to accelerate modelling of
the critical state magnetization current in a staggered-array bulk
high-temperature superconducting (HTS) undulator. The key concept is as
follows: i) a large magnetization current is first generated on the surface of
the HTS bulks after rapid field-cooling (FC) magnetization; ii) the
magnetization current then relaxes inwards step-by-step obeying the critical
state model; iii) after tens of backward iterations the magnetization current
reaches a steady state. The simulation results show excellent agreement with
the H-formulation method for both the electromagnetic and
electromagnetic-mechanical coupled analyses, but with significantly faster
computation speed. Solving the FEA model with 1.8 million degrees of freedom
(DOFs), the backward computation method takes less than 1.4 hours, an order of
magnitude or higher faster than other state-of-the-art numerical methods.
Finally, the models are used to investigate the influence of the mechanical
stress on the distribution of the critical state magnetization current and the
undulator field along the central axis.
