Analysis of ITER NbTi and Nb₃Sn CICCs experimental minimum quench energy with JackPot, MCM and THEA models

Abstract

Cable-in-conduit conductors (CICCs) for ITER magnets are subjected to fast changing magnetic fields during the plasma-operating scenario. In order to anticipate the limitations of conductors under the foreseen operating conditions, it is essential to have a better understanding of the stability margin of magnets. In the last decade ITER has launched a campaign for characterization of several types of NbTi and Nb3Sn CICCs comprising quench tests with a singular sine wave fast magnetic field pulse and relatively small amplitude. The stability tests, performed in the SULTAN facility, were reproduced and analyzed using two codes: JackPot-AC/DC, an electromagnetic-thermal numerical model for CICCs, developed at the University of Twente (van Lanen and Nijhuis 2010 Cryogenics 50 139–148) and multi-constant-model (MCM) (Turck and Zani 2010 Cryogenics 50 443–9), an analytical model for CICCs coupling losses. The outputs of both codes were combined with thermal, hydraulic and electric analysis of superconducting cables to predict the minimum quench energy (MQE) (Bottura et al 2000 Cryogenics 40 617–26). The experimental AC loss results were used to calibrate the JackPot and MCM models and to reproduce the energy deposited in the cable during an MQE test. The agreement between experiments and models confirm a good comprehension of the various CICCs thermal and electromagnetic phenomena. The differences between the analytical MCM and numerical JackPot approaches are discussed. The results provide a good basis for further investigation of CICC stability under plasma scenario conditions using magnetic field pulses with lower ramp rate and higher amplitude.

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

“…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.…”

“…THEA is a thermal code modeling the coolant flow inside the conductor and it is able to reproduce the thermal quench and its propagation. The two models were combined to study the stability tests performed on the SULTAN sample CSJA8 in [7]. The combination of models was used to study the CS conductor performance subjected to longer sinusoidal magnetic field pulses, more relevant to plasma operating condition in [6].…”

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

“…The testing boundary conditions used for the stability simulations are summarized in Table 4. In the following paragraphs, the simulation results for 1 s and 5 s single sinusoidal magnetic field pulse period will be analyzed and compared with the 0.128 s pulse period results from [9]. The sine wave is chosen in order to minimize the difference between the model and the SULTAN fast pulse experiment and to clarify the influence of the pulse period and amplitude.…”

Development of a New Generic Analytical Modeling of AC Coupling Losses in Cable-in-Conduit Conductors

“…It is an electromagnetic and thermal model that describes the AC/DC performance of CICCs and joints at strand level detail [26]. This model is used to study effects of current distribution non-uniformity, optimization of cable patterns and ITER and DEMO conductor and joint stability [27].…”