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1982 -
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Within scientific collaboration between Soviet Academy of Sciences and Czech Academy of Sciences, Department of Plasma
Physics of the Institute of Physics of Georgian Academy of Scinces was involved in joint experimental investi-
gations with Institute
of Plasma Physics of Czech Academy of Sciences on the tokamak TM-1-MH. This tokamak has been moved from Moscow
Kurchatov Institute to Prague, Czech Republic in order to establish tokamak research there.
In the framework of this collaboration Sulkhan Nanobashvili - Senior Researcher of the Institute, Candidate of Phys.-Math.
Sciences has been sent on a mission to Prague.
At that time general experimental investigations have been performed on the tokamak which involved investigation of edge
plasma properties and influence of lower hybrid waves on them. These were first results obtained on this tokamak, which were
published in scientific journal.
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1985 -
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Agreement has been concluded on joint scientific investigations in the direction of the investigation of thermonuclear plasma
between Institute of Physics of Georgian Academy of Sciences and Institute of Plasma Physics of Czech Academy of Sciences,
which exists up to now and is renewed once every 5 years.
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1985 -
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New multijunction grill was created in order to investigate lower hybrid wave interaction with plasma on tokamak CASTOR
(tokamak TM-1-MH modernised in 1983 - 1984.) Possibilities for generation of toroidal current – current drive – by means
of the grill were investigated, physical basics of 4-waveguide grill calculation were developed, the grill was designed, constructed
and active experiemtns were performedon tokamak (J. Dátlov, S. Nanobashvili, F. Žáček,
J. Stöckel, F. Jiranek and Tokamak team).
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1986 – 1987
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Lower Hybrid Current Drive was accomplished on tokamak CASTOR and regular study of plasma properties in this
regime has been performed. It has been discovered for the first time by us that in the current drive regime radial profile of
plasma current is significantly flattened compared to ohmic regime. This could cause significant influence on plasma turbulence,
which was confirmed during forthcoming investigations. In particular, plasma turbulence is strongly reduced in current drive
regime (S. Nanobashvili, F. Žáček, J. Stöckel, M. Valovič, V. Kopecky and Tokamak team).
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1988 -
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Systematic study of edge plasma turbulent properties started on tokamak CASTOR and later was continued on new tokamak
COMPASS. This remained as one of the main and permanent research topic regardless of the wide variation of the goals and
conditions of experiments (J. Stöckel, I. Nanobashvili, S. Nanobashvili, F. Žáčekand and Tokamak team)
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1994 -
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Physical basics for lower hybrid wave excitation on tokamak CASTOR by means of quasipotical grill were developed
(J. Preinhaelter) and quasioptical grill was designed based on this concept (S. Nanobashvili).
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1995 -
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Quasioptical grill was constructed in mechanical shop of Prague Institute of Plasma Physics, grill was tuned, installed and
active experiments started on tokamak CASTOR. (S. Nanobashvili J. Preinhaelter, F. Žáček).
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1995 -
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Experiments in electrode biasing regime started and were actively continued during forthcoming decade on tokamak
CASTOR. In the biasing regime nonuniform radial electric field is generated in plasma, which caused plasma polarization and its
effective sheared poloidal rotation. This had significant influence on plasma electrostatic and magnetic fluctuations, namely, these
fluctuations were dramatically reduced (J. Stöckel,F. Žáček, S. Nanobashvili, I. Nanobashvili and Tokamak team).
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1996 -
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It was demonstrated experimentally on tokamak CASTOR that in front of both - multijunction and quasipotical grills
nonuniform radial electric field is generated in plasma, which creates in edge plasma well-known biasing effect. This result is
important, because in this regime electrode is not inserted in plasma and we deal with contactless biasing. Thus, we obtain very
important possibility for external control of turbulence in high temperature fusion plasma
(F. Žáček, S. Nanobashvili)
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1996 -
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Statistical analysis of tokamak plasma turbulent fluctuations started on tokamak CASTOR (I. Nanobashvili, J. Stöckel,
S. Nanobashvili)
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1996 -
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Waveguide schematics was developed and built by us (S. Nanobashvili, I. Nanobashvili) for 8 mm range 3 frequency
(29GHz, 31 GHz and 33 GHz) poloidal and toroidal correlation reflectometer. Emitting and receiving antenna system for both
O- and X-mode consisted of 3 horn antennas. Central – emitting antenna was oriented in central – toroidal plane, upper
and lower antennas were oriented towards tokamak discharge chamber center, forming 15° angle with respect to the toroidal
plane. This system functioned flawlessly for many years on CASTOR tokamak under various experimental conditions and was
practically standard diagnostics for the tokamak.
Soon we have found phase runaway effect during experiments. As further analysis showed this was related with Doppler shift of
the frequency of signal reflected from poloidally rotating plasma. This is evidently good possibility for measurement of plasma
poloidal rotation speed (S. Nanobashvili, F. Žáček, P. Plisek).
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1998 -
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It was detected experimentally for the first time by us significant broadening of the spectrum of lower hybrid waves injected
into tokamak turbulent plasma by means of multijunction grill. This was entirely in agreement with theoretical investigations
(R. Klima, J. Preinhaelter, F. Žáček, S. Nanobashvili, J. Stöckeland and Tokamak team).
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2001 -
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Highly sensitive microwave method was created by us for applied research department of Prague Institute of Plasma
Physics. This method allowed to measure dielectric constant and loss angle tangent of boron carbide deposited on metallic or
dielectric surface. These measured parameters are very important in technology of Ultra-High Frequency component
manufacturing (S. Nanobashvili.)
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2002 - 2005
and
2006 - 2009
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During these years group of our Institute working on tokamaks (S. Nanobashvili - Head of the
group,
I. Nanobashvili, G. Rostomashvili, G. Gelashvili, M. Mdivnishvili) together with leading plasma centers of
Europe (including Institute of Plasma Physics, Czech Academy of Sciences) had INTAS international grant. The grant project
was devoted to investigation of plasma turbulence on different European tokamaks and development of methods for its external
control, also to study of the possibilities for improved confinement of thermonuclear plasma in magnetic trap. This project was
recognized by INTAS as one of the best for that period of time.
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2002 - 2003;
2005 - 2007
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I. Nanobashvili, Senior Researcher of the Department of Plasma Physics of our Institute, Candidate of Phys.-Math.
Sciences, started work on the superconductive tokamak TORE SUPRA in the Department of Investigations of
Controlled Fusion, Cadarache Center of French Atomic Energy Commissariat. He performed experimental investigation of edge plasma turbulence under various
experimental conditions by means of movable – so called “plunging” probe system.
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2006 -
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New method – “method of bursts” was proposed for investigation of edge plasma turbulent processes. This method allows to
understand deeper physical nature of turbulent processes which take place in tokamak edge plasma and helps to develop the
methods for their external control (I. Nanobashvili).
This method has been intensively used for the analysis of plasma turbulent transport in TORE SUPRA, CASTOR and
TEXTOR tokmaks.
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2010 -
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I. Nanobashvili started experimental investigations on the TEXTOR tokamak
in Research Center Julich. These investigations included study of influence of dynamic ergodic divertor on edge plasma turbulent characteristics. Experimental
data analysis by means of the “Method of Bursts” showed that in certain regime dynamic ergodic divertor has an influence on edge plasma turbulence, which is
similar to the effect of electrode polarization – so called biasing. This is very important for high temperature tokamak plasma, because of possibility for external
control of edge plasma turbulence by means of contactless polarization (biasing).
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December 2006 -
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Tokamak CASTOR operation at Prague Institute of Plasma Physics was stopped and it was moved to Czech
Technical University, where it operates now under the name GOLEM. This was done in the framework of EURATOM.
agreement between the states according to which tokamak COMPASS-D was moved to Prague Institute of Plasma Physics
from Culham (UK) and new program of thermonuclear plasma investigation was launched.
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2007 -
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“Method of bursts” proposed by I. Nanobashvili on the Tore Supra tokamak has been widely applied for the analysis of
edge plasma turbulent fluctuation data (fluctuations of plasma density and floating potential) from existing database of CASTOR
tokamak (I. Nanobashvili, J. Stöckel, P.devynck, S. Nanobashvili, G. Van Oost, P.Peleman).
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December 2008 -
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Tokamak COMPASS-D Dstarted operation at the Prague Institute of Plasma Physics. On this tokamak
experimental investigation of plasma turbulence and related processes continued in the framework of the agreement which
existed (and still exists) between our Institute and Prague Institute of Plasma Physics.
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2008 -
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Systematic study of electron cyclotron and electron Bernstein wave emission from plasma started on Tokamak
COMPASS-D Dby means of the Ultra-High Frequency (UHF) radiometer. For this purpose special stainless steel spherical and
elliptic mirrors were created. They are placed in limiter shadow and are externally adjustable. UHF wave emitted from quartz
window of vacuum chamber was detected by special horn antenna and signal was supplied to the 16 channel UHF radiometer.
This system was designed by us (S. Nanobashvili) and was manufactured in mechanical shop of Prague Institute of Plasma
Physics. Entire system was installed on the tokamak, tuned and started operation in different discharge regimes, including neutral
beam heating. Experimental investigations and theoretical analysis of results continued for many years until the end of Tokamak
COMPASS-D functioning in December 2020 (J. Preinhaelter, S. Nanoba-
shvili, F. Žáček, J. Urban, J. Zajac).
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2009 –
till now
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We are entirely involved in development of Ultra-High Frequency diagnos tics for investigation of high density hot
thermonuclear plasma on tokamak COMPASS-D and new tokamak COMPASS-U Uwhich is under construction. In particular,
we adapt existing diagnostics and also create new ones. This involves plasma interferometry, reflectometry and
radiometry (M. Varavin, J. Zajac, F. Žáček, S. Nanobashvili).
First of all we develop interferometer for high density - n≥1020 m3 plasma. This is submillimeter range, straight-showing
(unambiguous), double frequency system, antenna system adapted for vacuum chamber, detecting device and connection with
database. Work in this direction is close to its practical accomplishment. Millimeter range reflectometer UHF system which
functioned of COMPASS-D tokamak seems to be entirely valid for new tokamak, but antenna system requires serious
adaptation to new tokamak discharge chamber.
As for the radiometer antenna system, work in this direction will start in near future. Generally, design process of COMPASS-U
tokamak is finished and now its major components are manufactured. The tokamak entire assembly and testing is planned in 2023-2025.
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2025 -
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It is planned to obtain first plasma on COMPASS-U tokamak.
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