Research

My current research interests include studies of plasma waves and particle properties in magnetized sources and diagnostic development.

Laser diagnostics for fundamental studies

PRAXIS (PRopulsion Analysis eXperiments via Infrared Scattering)

Coherent scattering investigations of Hall thruster physics with PRAXIS at the national thruster facility PIVOINE-2G, Orléans

  • developed during my PhD, in collaboration with colleagues from the LPP, Ecole Polytechnique, and IJL, Nancy
  • applied to the microturbulence studies in Hall thrusters and more recently, planar magnetrons: identification of instabilities implicated in anomalous electron transport, as well as other modes. This diagnostic exploits coherent (or collective) Thomson scattering to measure very weak electron density fluctuations associated with such instabilities, on the order of 1% or below.

Plasma instabilities play a key, complex role in the operation of a range of plasma sources, yet it is not always feasible to study them with traditional diagnostics such as Langmuir probes. Work with coherent Thomson scattering has revealed the presence of the electron cyclotron drift instability in thrusters and planar magnetrons for the first time, and the presence of other modes, such as two-species ion streaming instabilities. Improving physical insights into such instabilities gives us clues as to how theory and numerical simulations need to be adapted. 

 

THETIS (THomson scattering Experiments for low Temperature Ion Sources)

Incoherent Thomson scattering implementation for measurement of hollow cathode electron properties at the ICARE Electric Propulsion Team facility, Orléans

  • developed with my PhD student, B. Vincent, and in the context of an ongoing collaboration with colleagues from LPGP, Orsay, and CEA Saclay
  • intended for measurement of absolute electron properties (density, electron energy distribution functions, drift velocity) in different plasmas. These plasmas include Hall thrusters, hollow cathodes, planar magnetrons and electron cyclotron resonance ion sources. This diagnostic is based on incoherent Thomson scattering and is specifically optimized to maximize the scattered signal recovered in very low-density plasmas (1016 particles /m3).

Conventional diagnostics for electron properties require a number of limiting assumptions and possess drawbacks such as plasma perturbation. Optical diagnostics such as incoherent Thomson scattering are more challenging to implement, but can yield more reliable information. This incoherent Thomson scattering diagnostic for low-density plasma investigations has provided new insights, including: evidence for deviations from Maxwell-Boltzmann electron energy distribution functions, anisotropies in electron temperatures, and the presence of high energy electrons.

Plasma sources

Studies so far undertaken involve a range of magnetized and unmagnetized devices:

Views of plasma sources: Hall plasma thruster, hollow cathode, planar magnetron, ECR plasma. These sources are relevant for applications such as plasma propulsion, thin film fabrication and ion generation in particle accelerators.


Collaborators, past and present

  • ICARE, Orléans: S. Mazouffre, Electric Propulsion team head
  • LPP, Ecole Polytechnique, Palaiseau: C. Honoré, D. Grésillon
  • CPHT, Ecole Polytechnique, Palaiseau: A. Héron, J-C. Adam
  • LPGP, Orsay: T. Minea, A. Revel, C. Ballage
  • CEA Saclay: J. Fils, O. Tuske, J. Schwindling
  • LAPLACE, Toulouse: L. Garrigues
  • IJL, Nancy: N. Lemoine, J. Cavalier
  • Univ. of Greifswald, Germany: K. Matyash, R. Schneider
  • PPPL, Princeton, USA: Y. Raitses
  • Stanford University, USA: K. Hara, M. Cappelli