PhD subjects

5 sujets IRFU/DACM

Dernière mise à jour : 17-09-2019


• Accelerators physics

• Electromagnetism - Electrical engineering

• Mechanics, energetics, process engineering

• Solid state physics, surfaces and interfaces

• Thermal energy, combustion, flows

 

Light Ion Source Optimisation for High Intensity production

SL-DRF-19-0298

Research field : Accelerators physics
Location :

Département des Accélérateurs, de Cryogénie et de Magnétisme (DACM)

Laboratoire d'Etudes et de Développements pour les Accélérateurs (LEDA)

Saclay

Contact :

Olivier TUSKE

Starting date :

Contact :

Olivier TUSKE

CEA - DRF/IRFU/SACM/LEDA

+33 1 69 08 68 20

Thesis supervisor :

Olivier TUSKE

CEA - DRF/IRFU/SACM/LEDA

+33 1 69 08 68 20

Since more than 20 years, CEA Saclay developed and built high intensity ion sources for accelerators, mainly heated by the electronic cyclotronic resonnant mechanism (ECR). The experience of the CEA is well recognize worldwide, our group was chosen to built ion sources for different facilities: IFMIF/LIPAc (Japan), SPIRAL2 facility (France) and FAIR in Germany.

High performances, in particular the high reliability of our ions sources made them essential for futur high intensity neutron source for fusion reactor material research, or experiences in neutron diffraction or cancer cure with the boron neutron capture therapy (BNCT).

The aim of this thesis is to provide us to a better understanding of the physical phenomena inside the ion sources, as the microwave-plasma interaction/coupling, or the plasma confinement. The primary goal is to optimize beam quality for ions sources, in term of stability in time, in homogeneity and purity but also to increase the extracted current far beyond actual performances. Compact ion sources with a better efficiency are also expected.

This ambitious program could be only validated with various experimental measurements at Saclay on a plasma reactor or on an extracted intense light ion beam with dedicated diagnostics.

Mastering high intensity beam production is the key of the future. Those innovative ion sources will play a large part in maintaining CEA leadership in the field of light ion sources and also in particles accelerators.

Contribution to the high gradient and large aperture superconducting accelerator magnets developments using of high magnetic field superconductors

SL-DRF-19-0768

Research field : Electromagnetism - Electrical engineering
Location :

Département des Accélérateurs, de Cryogénie et de Magnétisme (DACM)

Laboratoire d'Etudes des Aimants Supraconducteurs (LEAS)

Saclay

Contact :

Thibault LECREVISSE

Pascal TIXADOR

Starting date : 01-10-2019

Contact :

Thibault LECREVISSE

CEA - DRF/IRFU/DACM/LEAS

+33 (0)1 69 08 68 27

Thesis supervisor :

Pascal TIXADOR

CNRS -

Laboratory link : http://irfu.cea.fr/dacm/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=297

The Large Hadron Collider (LHC) at CERN is now in exploitation phase. The European physicians on particle physic community has already started the conceptual studies for the Future Circular Collider (FCC) with a collision energy increase to nearly 100 TeV to go deeper in the LHC studies possibility (14 TeV). Such a device would keep the leadership position of the European community in term of high energy physics. In the interaction (IR) area of this accelerator, few specific quadrupole magnets are needed in order to increase the luminosity (the number of collision with time unit) and the statistic related to new particles discovery. Such magnets have to generate a high magnetic field gradient in the largest possible aperture. High Field Superconductors (HFS, also called High Temperature Superconductors: HTS) would find here a use justification considering the higher cost compared to classical Low Temperature Superconductors (LTS).

We are proposing to demonstrate the feasibility of an interaction quadrupole magnet with a gradient over 150 T/m (1.5 time the FCC IR quadrupole gradient) in an aperture of 210 mm (design FCC). Such magnets will require specific design consideration and optimization, new winding technics and insulation process to be able to protect it against fast resistive transition.

The PhD student will interact with DACM team in order to design a quadrupole magnet corresponding to the accelerators requirement. A design step will be necessary in order to develop the fabrication process. Nevertheless the student will be able to look at specific aspect of the magnet fabrication, like the insulation or the protection aspects in such very high energy magnets.

Study of the Thermomechanical Behavior of the Superconductor Nb3Sn in Coils for Future Accelerator Magnets

SL-DRF-19-0486

Research field : Mechanics, energetics, process engineering
Location :

Département des Accélérateurs, de Cryogénie et de Magnétisme (DACM)

Laboratoire d'Etudes des Aimants Supraconducteurs (LEAS)

Saclay

Contact :

Etienne Rochepault

Olivier Hubert

Starting date : 01-10-2019

Contact :

Etienne Rochepault

CEA - DRF/IRFU/DACM

01 69 08 37 75

Thesis supervisor :

Olivier Hubert

ENS Pari-Saclay - LMT

01 47 40 22 24

Personal web page : https://www.researchgate.net/profile/Etienne_Rochepault

Laboratory link : http://irfu-i.cea.fr/dacm/index.php

In order to develop future particle accelerators such as the Future Circular Collider (FCC), high field superconducting electromagnets (higher than 15 T) are necessary. The superconductor Nb3Sn is aimed, however it causes some technical issues yet not solved during its production. The Nb3Sn is produced in the form of cables of the Rutherford type. These cables are then wound to form the coils of the electromagnet. Following winding, the conductor requires a heat treatment at 650°C in order to form the Nb3Sn superconducting phase. It is now established that significant dimensional changes of the strands occur during this phase change, translating in dimensional changes of the cables. If these changes in dimensions are not permitted by the tooling, mechanical stress add up in the coil and the superconducting performances degrade. Currently this issue is dealt with empirically by allowing clearances in central posts, around which are wound the superconducting cables, and by varying iteratively the clearances. However, the thermomechanical behavior of the Nb3Sn cables in a coil during the heat treatment needs to be quantified. The goal of this thesis is to observe and understand the changes of dimensions of this type of Nb3Sn conductors in order to help dimensioning the coil fabrication tooling for future accelerator magnets, and potentially improve their performances.

Nano Hetero structure for next generation superconducteurs under intense RF fields

SL-DRF-19-0425

Research field : Solid state physics, surfaces and interfaces
Location :

Département des Accélérateurs, de Cryogénie et de Magnétisme (DACM)

Laboratoire d’Intégration et Développement des Cavités et Cryomodules (LIDC2)

Saclay

Contact :

thomas proslier

Claire ANTOINE

Starting date :

Contact :

thomas proslier

CEA - DRF/IRFU/SACM/LIDC2

0169088711

Thesis supervisor :

Claire ANTOINE

CEA - DSM/IRFU/SACM/LIDC2

+33 169 08 73 28

Laboratory link : http://irfu.cea.fr/dacm/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=3301

Since their discoveries at the beginning of the twentieth century, the unique properties of superconductivity have been used in a wide variety of applications from powerful electromagnets used in MRIs and fusion reactors, to next generation electronic fast digital circuits (Quantum-bits) and particle accelerators. Major causes for performance limitations in a superconductor originate from its interaction with external electro-magnetic fields which are responsible for the entire electromagnetic behavior of applied superconducting materials. We propose an original approach to mitigate the superconducting dissipation originating from deleterious vortices: a new superconducting multilayer as efficient screening structure to inhibit vortices entry into the bulk superconductor. The synthesis and design of these nano hetero-structures by Atomic Layer Deposition will be optimized and tailored to drastically improve the performance of a superconductor-based device: superconducting radio frequency (SRF) cavities.

The PhD student will be an important active part of the synergistic approach between synthesis, design, characterization and performance tests of the most effective screening hetero-structures based on the superconducting nitride alloys NbN, NbTiN, MoN and insulating materials AlN, MgO, SrTiO3 in order to provide a technological breakthrough towards unprecedented superconductor performances for superconducting resonators. This 3 years program will focus on three research thrusts or work packages:

1- Explore synthetic routes to deposit innovative hetero-structures. Years 1-2.

2- Tailor hetero-structure properties to optimize superconductor performances. Years 2-3

3- Test optimized hetero-structure on superconducting Nb resonators. Year 3.

Study and modelling of the thermohydraulic phenomena taking place during the quench of a superconducting magnet cooled with supercritical helium

SL-DRF-19-0878

Research field : Thermal energy, combustion, flows
Location :

Département des Accélérateurs, de Cryogénie et de Magnétisme (DACM)

Laboratoire Cryogénie et Stations d'Essais (LCSE)

Saclay

Contact :

Walid ABDEL MAKSOUD

Bertrand BAUDOUY

Starting date :

Contact :

Walid ABDEL MAKSOUD

CEA - DRF/IRFU/DACM/LCSE

Thesis supervisor :

Bertrand BAUDOUY

CEA - DRF/IRFU/DACM/LCSE

0169084207

Nowadays, superconducting magnets are more and more used for applications related to the future energy. Indeed, they represent one main component of the so-called "Tokamak" machines which goal is to produce one day electricity from thermonuclear fusion energy. In order be in a superconducting state and to transport high current densities, these magnets are cooled by supercritical helium at a temperature of 5 K. However, a disturbance or fault in the machine could induce a heat deposition on the conductor and make it transit from his superconducting state to a normal resistive state. Once the conductor is resistive, the high current passing in it induces high heat deposition by joule effect and thus a transition of the conductor lengths close by. This transition chain reaction of the conductor from its superconducting state to its normal state is called "Quench". In the Framework of a collaboration between Europe and Japan, 20 superconducting magnets of the JT60SA Tokamak were tested by CEA under their nominal operating conditions (25 kA and 5 K). Quench experiments have been performed on each one of them. The PhD work will consist first in the physical analysis of the data obtained during quench experiments and the identification of the physical phenomena taking place during a quench. Then the PhD student may propose and carry out new complementary experiments allowing him to better understand the main thermo-hydraulic phenomena taking place. Finally, the PhD student will have to build a numerical model that reproduces and predicts the behavior of the magnets during a quench experiment. This model will be implemented in and existing industrial software.

 

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