5 sujets IRFU/DACM

Dernière mise à jour : 08-12-2021


• Accelerators physics

• Electromagnetism - Electrical engineering

• Radiation-matter interactions

• Solid state physics, surfaces and interfaces

• Thermal energy, combustion, flows

 

ADVANCED AND ARTIFICIAL INTELLIGENCE TECHNIQUES TO MITIGATE LINEAR AND NON-LINEAR IMPERFECTIONS IN FUTURE CIRCULAR COLLIDERS

SL-DRF-22-0514

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 :

Barbara Dalena

Starting date : 01-10-2022

Contact :

Barbara Dalena
CEA - DRF/IRFU/DACM


Thesis supervisor :

Barbara Dalena
CEA - DRF/IRFU/DACM


Personal web page : http://dalena.web.cern.ch/dalena/

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

After the discovery of the Higgs boson at the LHC, particle physics community is exploring and proposing next accelerators, to address the remaining open questions on the underlying mechanisms and on the constituents of the present universe. One of the studied possibilities is FCC (Future Circular Collider), a 100-km-long collider at CERN. The hadron version of FCC (FCC-hh) seems to be the only approach to reach energy levels far beyond the range of the LHC, in the coming decades, providing direct access to new particles with masses up to tens of TeV. The electron version of FCC brings a tremendous increase of production rates for phenomena in the sub-TeV mass range, making precision physics studies possible. A first study has shown no major showstopper in the colliders’ feasibility but has identified several specific challenges for the beam dynamics: large circumference (civil engineering constraints), beam stability with high current, the small geometric emittance, unprecedented collision energy and luminosity, the huge amount of energy stored in the beam, large synchrotron radiation power, plus the injection scenarios. This thesis will focus on the optimization of the hadron option of the future circular collider against linear and non-linear imperfections (i.e. magnets alignments and their field quality). A key point of this thesis is the comparison of current advanced correction schemes to techniques based on machine learning. The application of these techniques to accelerators is one of current hot topics in the field and pursued worldwide.

Impact of the Mechanical Stress on the Training of High Field Superconducting Nb3Sn Magnets

SL-DRF-22-0561

Research field : Electromagnetism - Electrical engineering
Location :

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

Laboratoire d’Etudes des Aimants Supraconducteurs (LEAS)

Saclay

Contact :

Etienne Rochepault

Starting date : 01-10-2022

Contact :

Etienne Rochepault
CEA - DRF/IRFU/DACM

01 69 08 37 75

Thesis supervisor :


-


Personal web page : https://www.researchgate.net/profile/Etienne-Rochepault

Laboratory link : https://irfu.cea.fr/dacm/index.php

More : https://home.cern/science/accelerators/future-circular-collider

In order to increase performances of future particle accelerators, high field superconducting electromagnets (higher than 10 T), based on Nb3Sn, are being developed. The LEAS at CEA Paris-Saclay is involved in several projects consisting in the design, manufacture and test of superconducting magnet demonstrators generating up to 16 T. The high fields and high currents (>10kA) required, generate high stresses on the conductor. The main problematic of these magnets is the sensitivity to external perturbations: the simple energy release can provoke the brutal transition of the superconductor to the resistive state. It is possible to bring the superconductor to a stable state using a “training”, which consists in performing successive transitions in order to progressively modify the initial conditions. To do so, the stress state of the superconductor must be understood and mastered. The PhD student will lead the development and the setup of experiments aiming at studying the impact of the mechanical stress on the training of Nb3Sn magnets. In addition, the PhD student will be in charge of developing Finite Element Models which should allow the simulation of the training phase. This work should allow a better understanding and mastering of the phenomena in order to push forward the limits of Nb3Sn magnets.
improved secondary electron yield by atomic layer deposition

SL-DRF-22-0289

Research field : Radiation-matter interactions
Location :

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

Laboratoire d’Ingénierie de Systèmes Accélérateurs et Hyperfréquences (LISAH)

Saclay

Contact :

Juliette PLOUIN

Mohamed Belhaj

Starting date : 01-09-2022

Contact :

Juliette PLOUIN
CEA - DSM/IRFU/SACM/LISAH

+33 169 08 12 65

Thesis supervisor :

Mohamed Belhaj
ONERA - DESP

+33 5 62 25 25 66

Multipactor is a parasitic phenomenon that occurs in devices where a microwave is transmitted under vacuum such as electronic vacuum tubes for electron microscopy, resonant cavities and couplers for particle accelerators and microwave circuits. on board the satellites. It consists of an avalanche of electrons set in motion by a radiofrequency field which can cause, under certain conditions, a disturbance of measurements, damage or even destruction of RF devices.

This phenomenon is directly linked to the emission of so-called secondary electrons from a material when it is irradiated with electrons. The secondary electron production yield (SEY for Secondary Emission Yield) is therefore a crucial parameter if we want to greatly reduce the multipactor phenomenon.

This thesis project aims at the fundamental study of SEY of thin films synthesized by Atomic Layer Deposition (ALD). ALD is a thin film synthesis technique used in the microelectronics, photovoltaic, battery industries…, which allows unparalleled control of thickness and chemical composition down to the atomic level on complex surfaces. This deposition technique is therefore a remarkable tool for 1 / studying separately and in a controlled manner the impact of different alloys (chemical composition), and their thickness on the SEY and 2 / directly applying these optimized structures on "real »RF devices. This thesis will be done in collaboration between CEA and ONERA. It combines at the same time a proven deposition technique, means of spectroscopic surface characterizations of peaks and numerical simulations.
Study of coherence losses mechanisms in superconducting resonators by tunneling and X-ray spectroscopy

SL-DRF-22-0288

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

Starting date : 01-09-2022

Contact :

thomas proslier
CEA - DRF/IRFU/DACM

0169088711

Thesis supervisor :

thomas proslier
CEA - DRF/IRFU/DACM

0169088711

Superconducting resonators are used in a wide variety of application; from Qubits or single photon detectors to radio frequency cavities used in particle accelerators. Superconducting quantum bits (Qubits) have attracted increasing attention and significant public investment in recent years. One of the main challenges is to maintain coherence / quantum information long enough to be able to perform calculations. Nowadays, Qubits can achieve a coherence time of about 100 µs and superconducting cavities ~ 100 ms; current research aims at increasing these times by at least an order of magnitude. Although these two superconducting devices (Qubits and cavities) are very different (operating temperature, geometries, etc.), recent experiments indicate that similar microscopic mechanisms limit their performance; Impurities (two-level systems, magnetic impurities, etc.) present within the dielectrics or at the interface between the dielectric and the superconducting film have been identified as potential candidates for loss of coherence. In addition, the superconducting properties of films, and in particular their spatial variations, are also important parameters that limit the resonators performances, and must therefore be systematically characterized.

This thesis project, in collaboration with IIT in the USA, CEA/SPEC and CERN, aims at studying by tunneling (ST) and X-ray photoemission (XPS) spectroscopies these superconducting surface parameters as well as the characteristic spectral signatures of impurities on new materials used for superconducting cavities and bits. Quantum. The aim is to provide a detailed understanding of these phenomena, to establish correlations between the measurements taken on samples and the performance of superconducting devices and finally to be able to propose technological solutions to improve their performance.
Numerical and experimental study of a small cryogenic pulsating heat pipe

SL-DRF-22-0331

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 :

Bertrand BAUDOUY

Starting date : 01-10-2022

Contact :

Bertrand BAUDOUY
CEA - DRF/IRFU/DACM/LCSE

0169084207

Thesis supervisor :

Bertrand BAUDOUY
CEA - DRF/IRFU/DACM/LCSE

0169084207

Recently the development of passive thermal links with high efficiency attracts attention for the cooling of miniature devices and energy savings purposes. One such device is the Pulsating Heat Pipe (PHP), built from shaped capillary tubes usually closed. Due to the phase change phenomenon of the included working fluid, a PHP can transfer heat fluxes about several dozen Watts at room but also low temperature. Nowadays, the dynamic and thermal operation of PHP is not yet fully understood due to the lack of a real fundamental understanding of the two-phase heat and mass transfer coupling mechanism within the PHP. Hence, the design of such thermal links is based on heuristic methods based on experimental data and simple computations. This project aims at developing experimental and numerical tools to comprehend the capillary two-phase heat and mass transfers for this particular heat pipe and to implement such a small heat pipe in an MRI system. A small dimension heat pipe will be constructed and tested at CEA Paris-Saclay. The PHP heat and mass transfer modeling will be developed with an open-source software based on finite volume method (OpenFoam) at the Wroclaw University of Science and Technology (WUST).

 

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