PhD Research Project: Study and Characterization of a low pressure-high density plasma source

This work is part of a collaborative project between several CNRS laboratories CNRS with industrial partners and covering several scientific domains. The thesis subject is a first step and it be continued in the Consortium.

The Ph.D. student will work in the team TMP-D&S - Theory and Modeling of Plasmas - Discharges and Surfaces of LPGP. The thesis will be supervised by Prof. T. Minea (Univ. Paris-Sud/Paris-Saclay) with a significant implication of one post-doc as well as the assistance given by an engineer. During the thesis minimum two reports per year must be delivered.

The plasma micro-sources become very interesting due to their low energy consumption, and their high efficiency for gas ionization favoring the production of charged particles beams and providing high currents. The experimental study of the physics governing these discharges is crucial to understand and optimize these sources and aiming further others applications. The development of novel plasma sources, some of them designed and made at LPGP, require a deep knowledge of the involved phenomena. Two new configurations of discharges providing a well-focused charge particle beam are available in the lab. The fine characterization of the plasma and the flux of extracted particles is the objective of this thesis.

Four research axes are planned to be addressed in this study.

• (i) The experimental characterization of the ECR plasma operated at low pressure, but with the power density as high as possible. The goal is to quantify the plasma density and to estimate electron temperature. These studies should allow to explain the behavior of the extracted beams as function of the extraction voltage.
• (ii) The change of the extraction system should allow to find an optimum operation point for this plasma source such as the extracted current reaches its maximum. Particularly, the beam diagnostics far from the source is an important part of the thesis.
• (iii) Other excitations modes of the plasma wilt be tested and studied, namely bi-polar pulsed sources instead of the conventional ECR. These open new perspectives unexplored by now. The LPGP design and build high-voltage power supplies with evolutive features and very high reliability allowing to excite and operate very specific plasmas, different from the state of the art in the field.
• (iv) The numerical modeling of the extraction system of charged particles from the plasma will be performed using the know-how and the existing codes in the TMP-D&S team. Hence it becomes possible et estimate the beam profile extracted from the plasma source and the impact of the high voltage acceleration system. A comparison of the model calculations with experimental results will be performed as well.