Speaker
Marko Cvejic
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.2002.pdf
Current outflow to low-density plasma region of z-pinch with
pre-embedded axial magnetic field
M. Cvejić1 , D. Mikitchuk1 , R. Doron1 , E. Kroupp1 , C. Stollberg1 ,
A. L. Velikovich2 , J. L. Giuliani2 , E. P. Yu3 , A. Fruchtman4 , Y. Maron1
1 Weizmann Institute of Science, Rehovot 76100, Israel
2 Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375, USA
3 Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185-1186, USA
4 Holon Institute of Technology, P.O. Box 305, Holon 58102, Israel
Magnetic flux can be compressed within a conducting shell when the shell collapses by the
application of an external force. In z-pinch scheme, the conductor is plasma and it is imploded
by the J × B force due to a large current passed through it, see Fig.1. Compression of magnetic
flux and magnetized plasma is gaining interest due to the advances in producing plasmas of high
temperature and density for fusion purposes e.g.[1].
In our experiment, we employ a cylindrical configuration, in which an initial axial quasi-static
magnetic flux Bz0 (up to 0.4 T) is pre-embedded in an argon gas column. A high-power electric
discharge (300 kA, rise time 1.6 µs) then ionizes the gas and generates an azimuthal magnetic
field, creating a pressure that compresses the plasma inward together with the axial magnetic
field embedded in it. Non-invasive spectroscopic measurements of the azimuthal magnetic field
(Bθ ) evolution using recently developed spectroscopic method [2, 3] are presented. Systematic
measurements, performed for different initial Bz0 , show that with increasing initial values of
1
Bz0 , less current is flowing through the imploding Ar plasma shell. For Bz0 = 0.4 T, only ∼ 4
of the current if flowing through the imploding argon plasma whereas most of the current flows
at large radii, through a lower-density plasma. We conclude that even in the presence of a low
axial magnetic field (relative to the peak azimuthal magnetic-field) this effect is significant. Re-
markably, the low-density plasma does not implode under this considerable current, suggesting
a formation of a force-free configuration.
Bz References
[1] M. R. Gomez, et. al., Phys. Rev. Lett., 113, 155003,
Fr
(2014)
Jz Bθ
[2] D. Mikitchuk, M. Cvejic, R. Doron, E. Kroupp, C.
initial phase implosion phase stagnation phase Stollberg, A. L. Velikovich and J. L. Giuliani, A.
time Fruchtman and Y. Maron, submitted to PRL;
[3] G. Rosenzweig, E. Kroupp, A. Fisher, and Y. Maron,
Figure 1: Principle of magnetic flux compression by z- JINST 12, P09004 (2017)
pinch plasma
