Speaker
Andrey Vasil'evich Arzhannikov
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/O2.J202.pdf
Studying the mechanisms of sub-mm wave emission from plasma due to
two-stream instability of relativistic electron beam
A.V. Arzhannikov1,2 , V.S. Burmasov1,2 , I.A. Ivanov1,2 , A.A. Kasatov1,2 ,
S.A. Kuznetsov1,2 , M.A. Makarov1, K.I. Mekler1, S.V. Polosatkin1,2 , S.S. Popov 1,2 ,
A.F. Rovenskikh1, D.A. Samtsov1,2 S. L. Sinitsky1,2 , V.F. Sklyarov1,2,
V.D. Stepanov1,2 , I.V. Timofeev1,2
1
Institute of Nuclear Physics, SB RAS, Novosibirsk, Russia
2
Novosibirsk State University, Novosibirsk, Russia
Studying the mechanisms of electromagnetic wave emission from magnetized
plasma due to the development of two-stream instability of a high-current relativistic
electron beam (REB) is considerably important. The two-stream instability is a fundamental
process occurring in both cosmic and laboratory plasmas. In laboratory experiments, the
beam-plasma interaction allows one to generate high-power sub-mm waves with the
promptly varying frequency1 that is important for practical applications. In this paper, we
present the novel results on studying the mechanisms of sub-mm wave emission produced in
a REB-plasma system as a result of the two-stream instability development.
Experimental investigations are carried out at the GOL-PET device. In these
experiments, the high-power REB (0.7 MeV/ 20kA/ 10 μs) is transported through a plasma
column of 2 m length with the density np= (0.5÷2)1015 см-3 which is confined in corrugated
magnetic field with average induction Bm= 4.2 T and corrugation factor 1.5. We have
measured the temporal dynamics of the radiation spectra by a 8-channel polychromator with
semiconductor diodes for the frequency range 0.1÷0.5 THz and by an additional 2-channel
system of cryogenic sensors for 0.5÷0.9 THz one. It is found that the high level of spectral
power density of the radiation is mainly concentrated in two clearly distinct regions of
spectrum. For the plasma with density near 11015 см-3, the first frequency region is located
from 0.25 up to 0.35 THz, the second one from 0.6 up to 0.8 THz. The emission power in
these regions depends essentially on the radial profile of the plasma density in the cross
section of the plasma column. This profile is measured by Thomson scattering system
during the beam injection in eight points over the plasma column diameter.
We have compared the experimental results with existing theoretical models
describing the conversion of the beam-driven plasma oscillations into electromagnetic
radiation for the typical conditions of our experiments. It is found that for the first frequency
region the observed emission can be interpreted by the linear mode conversion2 of the
upper-hybrid branch of plasma oscillations to the electromagnetic radiation in the regions of
strong plasma density gradients. For the second frequency region the emission is occurred
due to merging of these oscillations at a high level of plasma turbulence3.
1. A.V. Arzhannikov, A.V. Burdakov, V.S. Burmasov, et al., IEEE Transactions on Terahertz Science
and Technology, Vol. 6, No. 2, P.245 (2016)
2. I.V. Timofeev, V.V. Annenkov, A.V. Arzhannikov, Physics of Plasmas 22, p.113109 (2015),
http://dx.doi.org/10.1063/1.4935890
3. A.V. Arzhannikov and I. V. Timofeev. Plasma Phys. Controlled Fusion 54, 105004 (2012).
http://dx.doi.org/10.1088/0741-3335/54/10/105004.
