Analysis and control of magnetized plasma column rotation in the frame of astrophysics accretion mechanisms study

Nom de l'entreprise / du laboratoire: PIIM UMR 7345
Adresse web: http://piim.univ-amu.fr/
Encadrant: Alexandre Escarguel
Date de début: octobre 1, 2024
Durée: 3 ans

Accretion disks are complex systems whose dynamics covers a large number of research fields. Stellar disks are indeed made of dust, neutral gas and plasmas orbiting around young or rising stars and seed planet formation [1]. In link with the observation capabilities of modern instruments such as James Webb space telescope [2], intense efforts are nowadays undertaken to explain accretion mechanisms and disk formation. The link with a Keplerian nature of rotating discs is thus still a matter of debate, which might be elucidated by setting up dedicated experimental devices. Laboratory plasma experiments with a controlled plasma rotation is an innovative way to explore such scientific questions.

Mistral is a cold magnetized plasma experiment with a constant magnetic field [3, 4 ,5, 6]. It is a canonical experiment to study various kind of instabilities of weakly magnetized plasmas such as centrifugal instabilities [7]. Rotating plasma are easily obtained, but there is a lack of control of the azimuthal differential rotation. The prediction of the rotation properties and the control of the flow profiles is still an open problem regarding rotating plasmas in devices. Indeed, previous works in our SoPlasma network (https://gitlab.com/soplasma/soplasma), including the MISTRAL device, have shown that rotation of plasmas cannot be modified far beyond the very thin plasma sheath regions at the boundaries using standard biased electrodes. Recent progress however provide a path to achieve this important objective. Indeed, theoretical [8] and experimental [9] studies indicate a capacity to modify plasma rotation using emissive cathodes. Another possible way to control the plasma column rotation is to control the energetic ionizing electrons in Mistral by independent concentric grids. This PhD is centered on how the boundary conditions affect the magnetized plasma column rotation in Mistral to find strategies to control its azimuthal differential rotation. After becoming familiar with the MISTRAL experiment and its diagnostics, the plasma column  rotation will be studied by controlling boundary conditions with different experimental configurations. The corresponding rotating instabilities will be characterized by rapid imaging and by space/time resolved probe acquisitions and experimental results will be compared with theory.

This project, being within the framework of AMIDEX (“Excellence initiative” of Aix-Marseille University) project “Table Top Accretion Disks”, is 50% funded. 50% other funds could be obtained with a specific Aix-Marseilles physics doctoral school call dedicated to 50% funded projects (ED352: https://ecole-doctorale-352.univ- amu.fr/en) or with the ANR project « Cantaloupe » (see attached file) which has passed the 1st phase of ANR selection (http://anr.fr).

 

References
[1] G. R. J. Lesur, J. Plasma Phys. 87 205870101 (2021)
[2] Burrows et al, Astrophys. J 473, 437 (1996)
[3] N. Claire, A. Escarguel, C. Rebont, F. Doveil, Phys.Plasma 25, 061203 (2018)
[4] A. Escarguel, Eur. Phys. J. D, 56, 209-214 (2010).
[5] Th. Pierre, A. Escarguel, D. Guyomarc’h, R. Barni, C. Riccardi, Phys. Rev. Lett., 92, 065004 (2004).
[6] S. Aggarwal, Y. Camenen, A. Escarguel, and A. Poye, Journal Plasma Phys., 89(3), 905890310 (2023).
[7] R. Gueroult et al, Phys. Plasmas 082102 (2017)
[8] B. Trotabas and R. Gueroult, Plasma Sources Sci. Technol. 31, 025001 (2022)
[9] V.Désangles et al, J. Plasma Phys. 87, 905870308 (2021) and Désangles, Ph.D. thesis, Ecole Normale Supérieure de Lyon, France (2018)

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Pour postuler, envoyez votre CV et votre lettre de motivation par e-mail à alexandre.escarguel@univ-amu.fr