PhD: Study of thermal runaway and quench in REBCO coils (M/F)

Job Description

Thesis Subject

High-temperature critical superconducting (HTS) materials, particularly those based on REBCO, enable the development of fully superconducting magnets capable of generating very high magnetic fields. The creation of magnets producing 20 T or more is a major challenge for physics (NMR, high-energy physics) as well as for the realization of compact Tokamaks, which have become highly attractive in recent years. The implementation of HTS REBCO materials for the production of high-energy-density magnets raises several scientific and technical challenges, particularly regarding the prevention of the consequences of losing the non-dissipative state, and especially the risk of thermal runaway (commonly known as a quench).
Solutions exist, such as removing the turn-to-turn insulation to homogenize dissipation and thus reduce the maximum temperature. Another approach involves the early detection of quench precursors through highly sensitive voltage measurements across the coil terminals: this is the solution developed in collaboration by G2Elab and the Néel Institute over several years. However, there is limited feedback on the effectiveness of these methods, as few prototypes are operational, especially for magnets with high operating currents and conductors composed of multiple REBCO tapes in parallel. It is therefore necessary to develop experimental and numerical study capabilities for quench dynamics in REBCO conductors and elementary windings, tailored to their specificities: a wide operating temperature range (4 K – 77 K) and high currents, initially up to several kA and later up to several tens of kA.
The objective of this thesis is to contribute to the development of these means, particularly in the context of the PEPR SupraFusion project. For the experimental part, the thesis work will initially rely on a test cryostat in the kA range, currently being assembled. The PhD student will be responsible for its commissioning and will have access to this tool throughout the thesis. This first test facility will provide valuable data on quench dynamics in winding models using a few tapes, such as those envisaged for high-field magnet projects. Associated with this test facility will be the development of sensitive instrumentation for the early detection of dissipation/quench, initially through voltage measurement, but other approaches (radio frequency, optical fiber, etc.) may also be considered. These developments will be carried out by the PhD student in collaboration with the CEA and other international partner teams (Tohoku University, Polytechnique Montréal). In parallel with this experimental work, the PhD student will collaborate with the G2Elab modeling team on numerical models of quench dynamics. This development will aim, in the long term, to enhance our ability to predict quench behavior, as well as to serve as a tool for analyzing the experimental data obtained. In a second phase, the experience gained from the implementation of this first test cryostat will enable the PhD student to contribute to defining the technological solutions required to provide the team with a higher-current test facility (in the 10 kA range), designed to be adaptable to the large-diameter magnets of the LNCMI. This will allow testing of very high-current conductors or sub-conductors necessary for large-scale applications such as fusion magnets, under external fields and thus with applied mechanical constraints.

List of expected and appreciated skills:

- experience in conducting complex experimental work with Electric applications and/or Cryogenics,
- numerical Modelling skills

Your Work Environment

Institut NÉEL is a CNRS unit (UPR 2940) under agreement with the University Grenoble Alpes. The laboratory is related to the CNRS Physique. It is located in Grenoble, in the heart of a unique scientific, industrial and cultural environment. It is one of the largest French national research institutes for fundamental research in condensed matter physics enriched by interdisciplinary activities at the interfaces with chemistry, engineering and biology. It consists of 450 employees, including 175 researchers.
CNRS is a public, scientific and technological organization.
The core mandate is to identify, to carry out or to have carried out, either alone or with partners, all research that advances science or contributes to the country's economic, social, and cultural progress. Internationally recognized for the excellence of its scientific research, the CNRS is a reference in the world of research and development, as well as for the general public.

The hosting team at Institut Néel is Magsup —Magnetism and Superconductivity —, which forms part of the MCBT department.













Magnetism and Superconductivity

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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