Quench simulation of a CICC model coil subjected to longitudinal and transverse field pulses

This paper describes the work done under a collaboration between the Nation al High Magnetic Field Laboratory (NHMFL), and Indian Institute for Plasma Research (IPR). The objective of our work was to simulate quench initiation and evolution as a tool to help IPR with data interpretation on a series o f model coil experiments. The model coil consisted of a solenoid pancake-wo und with a NbTi CICC (forced flow SHe at 4.5 K, 10 kA rated current at 5 T) . The intent of the experiment was to determine the conductor stability whe n subjected to longitudinal and transverse magnetic field pulses similar to those present in the full-size SST-1 fusion reactor. For that purpose, the model coil was mounted in a rather complex setup. The NHMFL's role was to create a computer simulation model to assist IPR in experimental data inter pretation. The computer code Gandalf L. Bottura, Quench analysis of large s uperconducting magnets. Part I: Model description, Cryogenics 1992;32(7):65 9 was used to simulate the quench tests performed on the model coil. The si mulations uncovered the need to modify the standard AC loss models to signi ficantly increase the contribution of the longitudinal (toroidal) pulsating field to match the observed quench initiation. With these modifications (p ointing to higher than expected AC losses), the computer simulations matche d the experiment very closely in terms of quench initiation. Given the comp lexity of the geometry (leading to very non-uniform field distributions), q uench evolution was also complex, with multiple initial normal zones that r ecovered, grew, or coalesced depending on the location. The computer simula tions were able to shed light on the quench evolution; however, agreement w ith the experimental data was not achieved, pointing to a possible problem with the calibration methods used in the experiment. (C) 2001 Elsevier Scie nce Ltd. All rights reserved.