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Reference : UPR3021-ISAZOL-024
Workplace : ORLEANS
Date of publication : Tuesday, October 08, 2019
Scientific Responsible name : Stéphane MAZOUFFRE
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 January 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Thesis title: Physics of an Helicon plasma thruster
Helicon plasma thrusters are electrothermal propulsion devices for spacecraft. Compared to other technologies like Hall thrusters and ion engines they offer several advantages: they are neutralizer-free and therefore have a high reliability, the electrode (RF antenna) is not in direct contact with the plasma, thus assuring a long operational life, and they are relatively simple and compact. They are therefore good candidates for various types of missions such as attitude control and orbit transfer of small satellites, scientific studies in low-Earth orbit and propulsion of robotic space probes in the context of Moon and Mars exploration.
Helicon thrusters rely on a low-pressure radio-frequency plasma discharge in ICP or preferably Helicon mode coupled to a magnetic nozzle. Ions are produced in the discharge from atoms of the injected propellant, typically xenon, and subsequently accelerated through the magnetic nozzle where the electron thermal energy is converted into ion kinetic energy. Expansion of the plasma behind the demagnetization region generates thrust and specific impulse. Current Helicon thrusters deliver around 10 mN of thrust, 1000 s of Isp with an efficient of about 15 %.
This thesis subject seeks to better understand the physics at play in these devices to increase and optimize performance and extend the lifetime in order to achieve large velocity increments. The goal is to answer open questions concerning the plasma discharge and the plasma expansion in vacuum, for instance: what is the role of plasma turbulence in energy transfer and dissipation? What are the electron properties and how are they related to operating conditions? What is the exact mechanism for ion acceleration? How do electrons detach from magnetic field lines? Are there interesting propellant options for improving performance and efficiencies?
To respond to these questions, this thesis will mainly involve experimental aspects. The student will apply laser-aided diagnostics and electrical diagnostics to the study of electron and ion dynamics and properties in the discharge and the nozzle of a RF reactor available at ICARE. These experiments will be coupled with numerical investigations carried out at the UC3M in Madrid.
located on the CNRS campus in Orleans, ICARE is a research unit of the CNRS (Centre National de la Recherche Scientifique) and its main research fields are combustion, environmental research and space propulsion. Information on the laboratory themes can be reviewed at the lab website. The student will join the ICARE Electric Propulsion Team.
The proposed study will be performed in the framework of the H2020 HIPATIA project, which is led by the Spanish SENER company, on development and optimization of helicon and RF plasma thrusters for spacecraft.
Constraints and risks
The student will work with vacuum chambers, RF power supplies and RF plasma discharges, and will use laser-based diagnostics such as LIF spectroscopy and Thomson scattering as well as electrical diagnostics like Langmuir probes, RPA and E×B probes.
Thesis work will be performed primarily at the ICARE laboratory in Orléans, but the student will collaborate with colleagues at the UC3M University in Madrid who work on modelling and numerical simulations. The student will perform short stays ( 1-2 week long) in Madrid.
The candidate should have an engineering degree and/or a master's diploma in physics. Experience with plasma physics, optics, and hands-on experimentation are advised. Knowledge in electric space propulsion is welcomed. Strong communication skills in English are preferable, as the candidate will be expected to interact regularly with foreign researchers and present work at international conferences. Candidates are expected to show intellectual curiosity and a readiness to develop familiarity with current plasma physics research related to the thesis topic.
Candidates should include a detailed CV with references and a motivation letter, to be addressed to the project supervisors using the CNRS job portal.
Interested candidates are invited to apply until mid-October, 2019. Interviews of selected candidates will take place before the end of October at ICARE or by videoconference.
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