Thesis Archives - Physics of the Interactions of Ions and Molecules

PhD Thesis (M/F) – Physics – 2024/2027

The present work deals with negative-ions for fusion applications in the context of the international project ITER and its successor DEMO, which aim to demonstrate controlled nuclear fusion for energy production. In tokamaks (nuclear fusion reactors), a plasma composed of deuterium and tritium is magnetically confined and heated to very high temperatures, around 1.5·108 K to achieve nuclei fusion. In the ITER and DEMO devices, the heating of the plasma will mainly be produced by Neutral Beam Injectors (NBI). The ITER NBIs are required to inject 1 MeV beams of neutral deuterium atoms (D) into the tokamak, providing plasma heating. The production of such D beams relies on neutralization of high- intensity D- beams. D- negative-ions are produced in a low-pressure plasma source and subsequently extracted, accelerated and neutralized. The only up to date solution to produce the high intensity (40 A) beam required is to inject in the plasma source caesium (Cs). Caesium deposits on all surfaces and lower the material work function, thus enhancing the capture of electrons by incoming deuterium ions or atoms. While the solution is efficient, it has many drawbacks that could complicate NBI operation.

Several laboratories in France are associated in the development of a completely new concept of Neutral Beam Injector. At PIIM laboratory we participate to this effort by focusing on the alternative solutions to caesium. The experiments are conducted on a small scale plasma reactor well equipped with many diagnostics allowing for in depth investigation of negative- ion surface production in caesium free plasmas. The goal is to find solutions to produce high yields of negative-ions without injecting caesium.

PIIM laboratory has developed many tools, both numerical and experimental, to study negative-ion surface production in low-pressure low temperature plasmas. It is proposed here to investigate the fundamental parameters of negative ion production and extraction in Cs-free hydrogen/deuterium plasmas by using these tools: Langmuir probes, mass spectrometry with energy analysis, Magnetized Retarding Field Energy Analysis, surface analysis such as Raman spectroscopy, SEM, XPS, UPS and the newly developed Photoemission Yield Spectroscopy (PYS) diagnostic allowing in situ measurements of material work function, a key parameter in negative-ion surface production… Materials with interesting electronic properties such as diamond will be investigated, as well as other insulators and recently developed innovative low work function conductive ceramics.

Skills and knowledge: Knowledge in plasma science and/or surface science is required. The experimental aspect of physic research must motivate the candidate.

GD/2 PhD Thesis (M/F) – Chemistry – 2024/2027

Context: Since fifteen years, the ASTRO team draws a unique scenario that starts from the primitive dense molecular cloud up to the development of a prebiotic chemistry at the surface of the early Earth. They develop experimental approaches questioning the origin of the organic matter observed in the various interplanetary bodies of our solar system. They demonstrated that a part of this matter could be related to the chemistry occurring during the collapse of the native dense molecular clouds and its evolution to a protoplanetary disk. The accretion step could have then led to an incorporation of a fraction of this primitive organic matter in asteroids and comets, where, depending on the body, secondary alterations could have occurred, leading to a new evolution of the organic content. As observed on Earth with the presence of meteorites, the organic content of interplanetary bodies may have been delivered at the surface of the early Earth, 4.3 to 3.8 Go ago. This extraterrestrial organic matter may have been an important reservoir of organic matter that could have played a role in the emergence of life on the early Earth.

Objectives the scientific project: The aim is to develop, under the supervision of Pr. Grégoire Danger and in collaboration with Dr. Robert Pascal and Dr Vassilissa Vinogradoff, prebiotic chemistry experiments in order to understand the chemistry occurring in the context of the early Earth. A reductionist approach will be developed that aims to investigate the reactivity possibly occurring in the known conditions of the early Earth, by working on simple chemical systems to understand the role of specific chemical compounds involving high energy components such as nitriles and species capable of overcoming their otherwise limited reactivity like thiols and others. Our research will focus on amino acid and sugar chemistries, as well as on the chirality evolution.
Situation of the position: He/She will integrate the current project developed in the reductionist approach. The candidate will be part of a unique interdisciplinary project in the ASTRO team at the PIIM laboratory of the CNRS/Aix-Marseille University. We week for a candidate with skills in analytical chemistry, physical chemistry and/or organic chemistry.

Administrative information:
– The position is for three years. The funding is part of the AMIDEX IMOTEP project AMX-22-RE-AB-190.
– Applicants must have a Master degree in analytical chemistry, physical chemistry or organic chemistry by the date of appointment.
– The starting date is no later than October 2024.
– Applicants should submit a cover letter, a CV, a statement (2 pages max) explaining interests and qualifications, and if available letters of recommendation.
– Review of applications will begin upon receipt until the position is filled and all applications received by the deadline will receive full consideration.
– Selected applicants will be interviewed. They will have to present their research background and to propose a project in relation with the aim of the current position. The selection of the candidate will be held after these interviews.

Application Deadline: June 1th, 2024
Audition Deadline: July 1th, 2024
Starting date: October, 2024
End Date: October, 2027
Attention To: Grégoire Danger – Email: gregoire.danger@univ-amu.fr

Selected references:
1. The transition from soluble to insoluble organic matter in interstellar ice analogs and meteorites, G. Danger*, A. Ruf, T. Javelle, J. Maillard, V. Vinogradoff, C. Afonso, I. Schmitz-Afonso, L. Remusat, Z. Gabelica and P. Schmitt-Kopplin, Astronmy and Astrophysics, 2022, 667, A120
2. Identify Low Mass Volatile Organic Compounds from Cometary Ice Analogs using Gas Chromatography coupled to an Orbitrap mass spectrometer associated to Electron and Chemical Ionizations. T. Javelle, M. Righezza, G. Danger*. Journal of Chromatography A, 2021, 1652, 462343
3. Exploring the link between molecular cloud ices and chondritic organic matter in laboratory. G. Danger*, V. Vinogradoff*, M. Matzka, J-C. Viennet, L. Remusat, S. Bernard, A. Ruf, L. Le Sergeant d’Hendecourt and P. Schmitt-Kopplin. Nature Communication, 2021, 12, 3538
4. Impact of phyllosilicates on amino acid formation under asteroidal conditions. V. Vinogradoff*, L. Remusat, H.L. McLain, J.C. Aponte, S. Bernard, G. Danger, J.P. Dworkin, J.E Elsila, M. Jaber. ACS Earth and Space Chemistry, 2020, 4, 1398-1407
5. The Prebiotic C-Terminal Elongation of Peptides can be Initiated by N-Carbamoyl Amino Acids. N. Abou Mrad, G. Ajram, J-C Rossi, L. Boiteau, F. Duvernay, R. Pascal and G. Danger*. Chemistry – A European Journal, 2017, 23, 7418-7421
6. 5-(4H)-Oxazolones as Effective Aminoacylation Reagents for the 3′-Terminus of RNA. Z. Liu, C. Hanson, G. Ajram, L. Boiteau, J-C Rossi, G. Danger, R. Pascal* Synthetic Letters, 2017, 28, 73-77
7. Characterization of interstellar/cometary organic residue analogs using very high resolution mass spectrometry, G. Danger*, F-R. Orthous-Daunay, P. de Marcellus, P. Modica, V. Vuitton, F. Duvernay, L. Le Sergeant d’Hendecourt, R. Thissen, and T. Chiavassa, Geochimica & Cosmochimica Acta, 2013, 118, 184-201
8. 5(4H)-Oxazolones as Intermediates in the Carbodiimide- and Cyanamide- Promoted Peptide Activations in Aqueous Solution, G. Danger, A. Michaut, M. Bucchi, L. Boiteau, J. Canal, R. Plasson, and R. Pascal*, Angewandte Chemie International Edition, 2013, 52, 611-614

IC/1 PhD Thesis (M/F) – Chemistry – 2024/2027

Titan, Saturn’s largest satellite, is the only satellite in the solar system to have a dense atmosphere (1.5 bar) composed mainly of nitrogen and a few percent of methane. Subjected to various sources of irradiation, this atmosphere constitutes a very reactive medium evolving by molecular growth and by permanent production of aerosols. Among the molecules formed, hydrocarbons (C6H6, C4H2…) and nitriles (HC3N, HCN…) are known to condense in the lower stratosphere and lead to the formation of icy particles (Figure 1). During their stay at the level of the lower atmosphere (stratosphere and troposphere), these particles are then subjected to radiation of wavelengths higher than 230 nm and presumably to GCR ions, and can thus evolve chemically
The objective of this project is to study the aging of the ice formed in the lower stratosphere of Titan. For that, the student will have to take in hand the experimental device (PIIM) in order to condense the molecules present in the stratosphere while making them undergo the average UV radiations and electronic bombardments. In order to analyze the results, the student will use infrared spectrometry, UV spectrometry and very high-resolution mass spectrometry. The student will have to travel to Grenoble and Caen to carry out some experiments and model the interactions of aerosols with ion sources from both a qualitative and quantitative point of view, in particular the dN/dE flux density of GCRs in the atmosphere.

Expected profile of the candidate
Candidates for the PhD position should have a Masters’ degree in chemistry, with major interest in spectroscopy, physical chemistry and analytical chemistry. The successful applicant will have obtained excellent grades in his/her Bachelor and Master’s degrees (or equivalent). He/she should be well motivated, hardworking, willing, and able to work as part of a team. Background / experience in astrochemistry would be beneficial, interest for planetology welcome. Applicants are invited to send their CV, a cover letter, their transcripts of academic records, and the contact information for at least two references to Isabelle Couturier (Isabelle.couturier@univ-amu.fr) before June 10.

Réf.:
1. I. Couturier-Tamburelli, M. S. Gudipati, A. Lignell, R. Jacovi, N. Piétri, Icarus 2014, 234, 81–90.
2. M. S. Gudipati, R. Jacovi, I. Couturier-Tamburelli, A. Lignell, M. Allen, Nat. Commun. 2013, 4, 1648.
3. J. Mouzay, I. Couturier-Tamburelli, N. Piétri, T. Chiavassa, J. Geophys. Res. Planets, 2021,126, e2020JE006566.
4. J. Mouzay, K. Henry, A. Ruf, I. Couturier-Tamburelli, G. Danger, N. Piétri and T. Chiavassa, 2021 Planet. Sci. J. 2 37.
5. I. Couturier-Tamburelli, G. Danger, J. Mouzay, C. Pardanaud & N. Piétri, 2024 The Journal of Physical Chemistry A 128, 3, 636–645.

Thesis – Physics – Modeling – 2212/TP/YE/2

The proposed thesis subject is : advanced shaping of wave-particle interaction in traveling wave tubes

Before addressing the details of this subject further down in the text, it is appropriate to specify for the attention of the candidates (F/M) the practical modalities of this thesis and of the preparation of the doctoral degree in which it is included.

This thesis is in the framework of a French PhD diploma, prepared at the doctoral school “Physics and Material Sciences” (ED252) of Aix-Marseille University. The start is planned for the fall of 2023. Half of the funding is provided by the French Centre National d’Etudes Spatiales (CNES) and the other half by the company Thales. For the successful candidate (F/M), it will take the form of a fixed-term employment contract called “doctoral contract” for a period of 3 years from 01/10/2023 to 30/09/2026. The employer would be the CNES and the thesis would take place at the PIIM laboratory in Marseille with regular travel to Thales in Velizy (Paris area). The selected candidate (F/M) would be consequently employed by CNES for 3 years, the work contract remaining conditioned by the continuation of the preparation of the PhD.

Thus, the applications will have to be, in due time, formalized with the CNES, on its application site, i.e. between 01/02/2023 and 15/03/2023 when the position is posted.

Before applying, it is strongly recommended to read very carefully the subject and then to contact as soon as possible by mail the future co-supervisors, Professor Yves Elskens (yves.elskens (at) univ-amu.fr) at the PIIM laboratory, and Frédéric André (frederic.andre (at) thalesgroup.com), research engineer at Thalesgroup (AVS Microwave and Imaging Systems).

This topic is also closely related to the internship offered at the laboratory from March to July 2023. It goes without saying that a successful internship on this topic finds its natural extension in the preparation of the PhD.

Thesis subject : advanced shaping of wave-particle interaction in traveling wave tubes

Wave-particle interaction is a fundamental process in the physics of hot and natural plasmas, accelerators and beams ; in particular, it is the basis of wave amplifiers such as free electron lasers, gyrotrons, traveling wave tubes… The power in some of these devices and their broad frequency spectrum lead to instabilities, nowadays increasingly critical and hard to simulate. A microscopic description enables a better understanding of the coupling mechanisms between N particles and the amplified radiofrequency waves using hamiltonian dynamics. For N → ∞, the dynamics of this system converges to the one described by vlasovian kinetic equations.

Numerical simulation currently relies on two types of models. Particle-in-Cell (PIC) models rest on a minimal simplification of physics equations but lead to huge computing times, as the number of degrees of freedom is very large. Specialized models, in contrast, allow simulating only particular regimes, but with outstandingly shorter times.

The very popular envelope model is a frequency-domain model in which the amplified wave is represented by the cold wave (the wave propagating in the absence of beams), multiplied with an envelope function varying with the position along the propagation direction. This frequency-domain approach is not fit for investigating nonlinear regimes, like saturation instabilities and intermodulation effects.

We developed a novel time-domain model with few degrees of freedom thanks to an efficient representation of fields, enabling a realistic simulation of amplification in traveling wave tubes. We shall confront these simulations with experiment in space traveling wave tubes and in the 4 metre long device which enabled our laboratory to perform the first direct observation of several fundamental processes of this physics.

The Ph.D. will focus on developing simple nonlinear models and using them numerically toward applications in particular to the traveling wave tubes of Thales Avionics (Vélizy) and in our laboratory (Marseille). Three specific research lines are being considered :

– adapting the current model (designed for uniform structures) to structures with space-dependent characteristics (tapers) ;

– describing more accurately the reflection processes at space-dependent defects ;

– investigating the operation of TWT with pulsed RF input (instead of permanent harmonic input) ; this pulsed regime may enable reachng much higher interaction efficiencies ; this physics is also relevant to other applications, aiming at accelerating particles using short pulses. A master degree internship is open with our team from March 2023.

References :
– Y. Elskens & D. Escande, Microscopic dynamics of plasmas and chaos (IoP Publishing, Bristol, 2003).
– F. André, P. Bernardi, N.M. Ryskin, F. Doveil & Y. Elskens, Hamiltonian description of self-consistent wave-particle dynamics in a periodic structure, Europhys. Lett. 103 (2013) 28004.
– D.F.G. Minenna, Y. Elskens, F. André & F. Doveil, Electromagnetic power and momentum in N-body hamiltonian approach to wave-particle dynamics in a periodic structure, Europhys. Lett. 122 (2018) 44002.
– Kh. Aliane, Y. Elskens, F. André & D.F.G. Minenna, Many-particle models and short pulse amplification in traveling wave tubes, IEEE Trans. El. Dev. 68 (2021) 6476-6481
– D.F.G. Minenna, Kh. Aliane, Y. Elskens, A. Poyé, F. André, J. Puech & F. Doveil, Time simulation of the nonlinear wave-particle interaction in meters long traveling-wave tubes, Phys. Plasmas 28 (2021) 092110
– PhDs in Marseilles : A. Macor (2007), A. Aïssi (2008), P. Bernardi (2011), S. Théveny (2016), D. Minenna (2019), Kh. Aliane (in progress).