Quench energy studies in ITER conductors for different magnetic field perturbations with Jackpot and THEA combined models

Abstract

The electromagnetic-thermal models for Cable-in-Conduit Conductors JackPot-ACDC and THEA (Thermal, Hydraulic and Electric Analysis of superconducting cables) are combined predicting the stability of ITER Central Solenoid conductors. The combination of both models allows the prediction of the effect of any type of magnetic field perturbation in time, relevant for the magnet coils during the plasma operation scenario of the reactor. At present, there is no experiment for testing the stability of the ITER Nb3Sn conductors under such conditions. Only limited experimental data on Minimum Quench Energy (MQE), defining the conductor stability, are available but the time and magnetic field amplitude settings are completely different from the actual ITER operating conditions. Nevertheless, such tests are useful as a basis to calibrate and benchmark the codes. The JackPot-THEA combination allows to determine the MQE for any magnetic field change in time and to fully describe the involved electromagnetic phenomena in strand-level detail in terms of local power dissipation and (peak) electric field along all strands. Thermally, the computation is still on a global scale for identifying the quench initiation and propagation. The predictions from the combined codes are in good agreement with the experimental results and provide a solid basis for extrapolative scaling of CICC's stability under plasma operating conditions.Disclaimer: The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.

Electromagnetic and thermal stability of the ITER Central Solenoid during a 15 MA plasma scenario

“…The stability of the conductor can be defined using the peak and average electric fields, as shown in [6]. The average electric field of the conductor is compared to the electric field at quench measured during the SULTAN DC T cs tests.…”

“…The stability is related to the time duration and space distribution of the disturbance [25]. As observed in [6], a conductor in transient condition is able to reach higher local electric field and power deposition depending on the pulse duration. The CSJA8 short sample peak electric field simulated with JackPot-THEA is used as a threshold to study the stability of the conductor.…”

“…In order to study the impact of the different effective strain on the electromagnetic performance of the CS, several simulations are performed varying only the effective strain applied to the superconducting strands. The results are presented in terms of peak and average electric field and compared to the stability electric field thresholds calculated with JackPot-THEA in [6], see figure 7. The peak and average electric fields during the plasma scenario are one order of magnitude lower than the stability threshold.…”

“…The SULTAN AC loss results after cycling of the CSJA8 sample are used to estimate the effects of current and magnetic field variation on the inter-strand contact resistance. The CSJA8 conductor sample was tested at three different conditions, for each of them JackPot solved an inter-strand resistivity to match the coupling loss results, see [6]. The CSJA8 test conditions, interstrand resistivities and coupling loss nτ are listed in table 1.…”

“…The second goal of this study is to model the thermal behavior of the most critical layer of the CSU2 pancake from inlet to outlet during a full 15 MA plasma scenario cycle and subsequent cycles. The simulation is performed using the Jack-Pot-THEA model as already validated and calibrated with the SULTAN short sample tests results in [6] and [7]. The simulation involves one layer of the CSU2 quadra-pancake, i.e.…”