Марко Цвејић

18. октобра 2019.

У оквиру семинара Лабораторије за спектроскопију плазме и ласере, у среду, 23. октобра 2019. у 12 часова у читаоници библиотеке „Др Драган Поповић“, Марко Цвејић (Weissman Institute of Physical Sciences, Israel) одржаће предавање:

Challenges in the investigation of compression of magnetized plasma


The seminar will refer to a compression of magnetic flux that is
initially embedded in a plasma that undergoes an implosion. The plasma
is produced in a Z-pinch configuration in which a gas puff load is
ionized and implodes under the J×B forces resulting from a 1-μs long,
300 kA, current pulse.
The subject of compression of magnetic flux and magnetized plasma is a
fundamental problem manifested in a variety of conducting fluid
phenomena in laboratory plasmas and astrophysics. Recently, this subject
has gained particular interest due to the advances in producing plasmas
of high temperature and density for fusion purposes, based on the
approach of magnetized plasma compression.
We report the first-time development and employment of spectroscopic
methods, based on the Zeeman effect and polarization techniques, to
measure both the compressed (axial) and the compressing (azimuthal)
magnetic fields throughout the implosion and stagnation processes. Time
and space resolved spectroscopic measurements showed that the
application of a relatively weak axial magnetic field (Bz0) has a
dramatic effect on the implosion dynamics affecting significantly the
current distribution in the plasma [1]. It was found that in the
presence of Bz a large part of the current does not flow in the
imploding plasma, rather it flows through a slow-imploding low-density
plasma (LDP) residing at large radii. Furthermore, it is observed that
the fraction of total current that flows in the LDP increases with Bz0.
We suggest an explanation of the phenomena, based on the development of
a force-free current configuration.
Previously unpredicted observations in high-power magnetized-plasma
experiments, including recent unexplained structures observed in the
Magnetized Liner Inertial Fusion experiment, may be connected to the
present discovery.
[1] Mikitchuk, D., Cvejić, M., Doron, R., Kroupp, E., Stollberg, C.,
Maron, Y., Velikovich, A. L., Ouart, N. D., Giuliani, J. L., Mehlhorn,
T. A., Yu, E. P., and Fruchtman, A. “Effects of a preembedded axial
magnetic field on the current distribution in a Z-pinch implosion”,
Phys. Rev. Lett. 122, 045001 (2019).