Speaker
Masayasu Hata
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.2022.pdf
Effects of strong external magnetic field on high-intense laser propagation
into dense plasma
M. Hata , H. Sakagami , T. Sano , Y. Sentoku , H. Nagatomo
1 2 1 1 1
1
Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka, Japan
2
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu, Japan
The establishment of method for generating kilo-tesla class magnetic field using
high-power laser allows us to perform experiments of high-intense laser plasma interactions
(LPI) under strong external magnetic field [1,2]. Such strong magnetic field affects not only
fluid dynamics but also fast electrons and laser propagation. Recently, it is proposed that
fast electrons of which divergence is very large are guided by kilo-tesla class external
magnetic field and heat core efficiently, and related experiments have been intensively
performed [3,4]. With recent progress of strong magnetic field generation in laboratory,
fundamental studies using such strong magnetic field have been performed and
high-intense laser plasma interactions under strong magnetic field have been opened up as
new research area. In this study, we pay attention to high-intense laser propagation into
dense plasma under strong magnetic field and have conducted two-dimensional
Particle-In-Cell (PIC) simulations of high-intense LPI with strong magnetic field.
Target plasma is made of hydrogen and its density profile in x direction consists of
preplasma which has exponential profile with scale length of 20 µm and flat plasma with
density of 40 n . The density profile in y direction is uniform. Applied external magnetic
cr
field along the direction of laser propagation, namely x direction, is set to 50 kilo-tesla.
Linearly polarized laser that has temporally flattop and spatially Gaussian profiles with spot
diameter of 20 µm irradiates the target with normal incidence. At least 500 fs of simulation
has been done using 2D PIC code.
According to the linear theory of cold plasma in strong magnetic field, right-handed
circularly polarized (RCP) component of electromagnetic wave propagates into dense
plasma without cut-off density. Simulation results show that initially RCP component of
injected laser can propagate in dense plasma, but after a while following laser cannot
propagate. It is found that strong ion acoustic wave generates at the area where laser cannot
propagate and it triggers the reflection of RCP component of the injected laser. In the
presentation, inhibition mechanism of laser propagation will be discussed in detail.
[1] S. Fujioka et al., Sci. Rep. 3, 1170 (2013).
[2] H. Yoneda et al., Phys. Rev. Lett. 109, 125004 (2012).
[3] T. Johzaki et al., Nucl. Fusion 55, 053022 (2015).
[4] M. Bailly-Grandvaux et al., Nature Comm. 9, 102 (2018)
