Speaker
Ezra van Lanen
(University of Twente)
Description
The twin-box pancake joints for the PF coils of ITER will be constructed by connecting overlapping sections of the cable-in-conduit conductors with copper soles. For the analysis of the stability of these joints in a plasma scenario, it is necessary to know how its coupling losses respond under different orientations of the background field. For this purpose, a new model has been developed based on JackPot, which can calculate the coupling losses in such a joint at strand level. It calculates the mutually induced voltages across strand and copper sole sections with Biot-Savart type equations which, due to the discretisation of the system, results in many tens of billions of mutual couplings. The Multi-Level Fast Multipole Method (MLFMM) has been implemented to calculate these couplings in an acceptable time. This method separates the system in groups of current carrying elements that are close to each other, for which the couplings are calculated directly, and in groups that are far away, in which case an approximation is used. Larger number of elements can be put into one group if they are farther away, for additional calculation efficiency. Since this method is highly suitable for parallel computation techniques, the code has been implemented for use on a Graphics Processing Unit (GPU).
The paper describes the implementation of the MLFMM in JackPot, and demonstrates the speedup that is acquired with it, at an acceptable tolerance. It also describes the results from coupling loss calculations on ITER PF pancake joints.
Author
Ezra van Lanen
(University of Twente)
Co-authors
Arend Nijhuis
(University of Twente)
Jeroen van Nugteren
(University of Twente)
