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Modelling-driven requirements for Error Field Control Coil application to initial JT-60SA plasmas

L. Pigatto, G. Frello, Y. Q. Liu, L. Novello, M. Takechi, E. Tomasina, T. Bolzonella

TL;DR

This work tackles modelling-driven requirements for applying Error Field Correction Coils (EFCC) to JT-60SA initial plasmas amid resonant error fields. It combines linear resistive MHD modeling with an overlap-field criterion, constructing a plasma-response database via Equivalent Surface Current and Singular Value Decomposition to predict core response to $n=1$ external fields. A Matlab/Simulink dynamic tool computes EFCC current references and models the power-supply/load dynamics to plan safe EF operation. Results indicate that EFCCs can operate within current/voltage limits while reducing EF penetration, providing a practical framework for ITER risk mitigation and guiding future multi-coil optimization.

Abstract

JT-60SA is a large superconducting tokamak built in Naka, Japan. After the successful achievement of its first MA-class plasma, the installation of several additional sub-systems, including a set of non-axisymmetric Error Field Correction Coils (EFCC), is ongoing. Optimization of future JT-60SA plasma scenarios will critically depend on the correct use of EFCC, including careful fulfillment of system specifications. In addition to that, preparation and risk mitigation of early ITER operations will greatly benefit from the experience gained by early EFCC application to JT-60SA experiments, in particular to optimize error field detection and control strategies. In this work, EFCC application in JT-60SA Initial Research Phase I perspective scenarios is modeled including plasma response. Impact of (Resonant) Magnetic Perturbations on the different plasma scenarios is assessed for both core and pedestal regions by the linear resistive MHD code MARS-F. The dominant core response to EFs is discussed case by case and compared to mode locking thresholds from literature. Typical current/voltage amplitudes and wave-forms are then compared to EFCC specifications in order to assess a safe operational space.

Modelling-driven requirements for Error Field Control Coil application to initial JT-60SA plasmas

TL;DR

This work tackles modelling-driven requirements for applying Error Field Correction Coils (EFCC) to JT-60SA initial plasmas amid resonant error fields. It combines linear resistive MHD modeling with an overlap-field criterion, constructing a plasma-response database via Equivalent Surface Current and Singular Value Decomposition to predict core response to external fields. A Matlab/Simulink dynamic tool computes EFCC current references and models the power-supply/load dynamics to plan safe EF operation. Results indicate that EFCCs can operate within current/voltage limits while reducing EF penetration, providing a practical framework for ITER risk mitigation and guiding future multi-coil optimization.

Abstract

JT-60SA is a large superconducting tokamak built in Naka, Japan. After the successful achievement of its first MA-class plasma, the installation of several additional sub-systems, including a set of non-axisymmetric Error Field Correction Coils (EFCC), is ongoing. Optimization of future JT-60SA plasma scenarios will critically depend on the correct use of EFCC, including careful fulfillment of system specifications. In addition to that, preparation and risk mitigation of early ITER operations will greatly benefit from the experience gained by early EFCC application to JT-60SA experiments, in particular to optimize error field detection and control strategies. In this work, EFCC application in JT-60SA Initial Research Phase I perspective scenarios is modeled including plasma response. Impact of (Resonant) Magnetic Perturbations on the different plasma scenarios is assessed for both core and pedestal regions by the linear resistive MHD code MARS-F. The dominant core response to EFs is discussed case by case and compared to mode locking thresholds from literature. Typical current/voltage amplitudes and wave-forms are then compared to EFCC specifications in order to assess a safe operational space.
Paper Structure (8 sections, 2 equations, 5 figures)

This paper contains 8 sections, 2 equations, 5 figures.

Table of Contents

  1. Introduction and background
  2. Error Field and plasma response modeling
  3. Development of dynamic simulation tool
  4. Calculation of overlap EF
  5. Calculation of EFCC current reference
  6. Modeling EFCC power supply
  7. Discussion
  8. Conclusion

Figures (5)

  • Figure 1: Geometry of JT-60SA Error Field Correction Coils, represented as 3D mesh.
  • Figure 2: Simulink block for calculation of overlap field.
  • Figure 3: Right y-axis: total overlap error field for CS1-2 (solid) and corrected overlap field (dashed). Left y-axis: plasma current assuming E100738 as possible target shot.
  • Figure 4: Time evolution of currents in upper EFCC. Reference wave forms are shown in red dashed lines, load currents as blue solid lines.
  • Figure 5: Coil currents in the Upper, Mid-plane, and Lower EFCC (independently operated) at t=3.5s during flat-top phase.