Transcript Hydrogen retention after boron carbide coating during plasma shot of tokamak Т11-М

Hydrogen retention after boron
carbide coating during plasma
shot of tokamak Т11-М
O.I. Buzhinskij , E.A. Azizov, V.G. Otroshchenko, V.P. Rodionova, N.B.
Rodionov, S.M. Sotnikov, I.Ya. Shipuk, S.N. Tugarinov, A.G. Trapeznikov
Presented by
Prof. Oleg Buzhinskij
Head of Boundary Physics
Federal State Unitary Enterprise State Scientific Center Troitsk,
Institute for Innovation and Fusion Researches,
Troitsk Moscow reg., 142190, Russia
June 1-4
SALAMANCA, SPAIN
2008
Troitsk Moscow reg., Russia
Experimental results on boronization in plasma
shots of the tokamak T-11M are presented. Nontoxic and not explosive metacarborane C2H12B10
was used in the boron deposition process.
Experiments have been carried out in shots with
parameters: toroidal field ~1-1.2 Т, plasma current
Ip = 70кА, average shot duration tp ~ 150ms and
electron density along the central chord ne ~
2.5∙1013 cm-3. As a result of experiment, a dense
film of ~ 0.2 microns thickness with good
adhesion to a surface has formed on the reference
specimens after 8 second boronization.
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
Crystalline boron carbide coating В4С, produced by
a method of the chemical vapor deposition in a
reactor from the fluoride phase at the temperatures
to ~ 2000°С, is widely used in the Russian
tokamaks [1]. The coating has a number of
substantial advantages before graphites: the small
chemical and physical sputtering, low ionstimulated desorption and radiation-accelerated
sublimation. As a result, a rate of the film erosion
and sputtering at ion and plasma irradiation in the
up-to-date accelerating and thermonuclear facilities
is much below, than for graphites [1]. These
characteristics vary a little up to the temperatures of
~ 1400°С.
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
Hydrogen
capture in boron
carbide in
several times is
less, than in finegrained, dense
graphites and
CFC composites
[2]. This
difference is
increased with
an irradiation
dose, hydrogen
capture in В4С is
saturated at
doses about 1023
аt/m2.
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
Thermal conduction of boron carbide is not high (20
W/mK), but the coating of thickness up to 100 μm,
deposited on graphites with high thermal
conduction, withstands high heat loads without its
destruction and integrity losses. In all experiments
the boron carbide coating showed a high resistance
to heat loads without destruction and integrity
losses, without changes in the chemical
composition and material structure. The best
coatings were at the deposition on graphites with a
high thermal conduction (RGT or pyrolitic
graphite) [5].
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
Boron carbide coating produced by chemical vapour
deposition has obvious advantages. However,
because of complex technology of production at high
temperatures a coating can be used in tokamaks only
at the stage of initial mounting, reconstruction and
modification of a discharge vessel. Boronization in a
glow discharge in-situ results in to formation of thin
amorphous films of thickness up to 100 nm [3,4].
Recently, boron carbide films with a composition
close to stochiometric В4С have been obtained on the
PISCES-B facility in the University of California,
San Diego. Deposition rate was extremely high and
achieved of ~30 nm/sec, that approximately in one
thousand times exceeds a rate of film deposition in a
glow discharge. Thickness of deposited layer
depended on discharge time and achieved of 40 μm
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
R - 0,7m
a - 0,2m
Bт - 1Т
Ip - 70kA
Poh ~ 100kVt
∆t ~ 0,1s
Crystalline metacarborane was placed in the glass
container that connected with high-vacuum
electromagnetic valve. Electromagnetic valve was
connected to a diagnostic port of the T-11M
tokamak discharge chamber through a vacuum gate
valve.
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
Boronization in the Т-11М tokamak was
carried out after operation with lithium
limiter without preliminary induction
heating and cleaning of chamber by a glow
discharge. In anterior shots (before
boronization) atomic lithium, and also
impurities came in plasma at the expense of
an ion sputtering from chamber walls.
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
A radiation spectrum of plasma before boronization is shown by red
colour. There is a bright line of Li ion in the plasma radiation
spectrum. However, already after several shots with carborane Li
line and impurities lines practically vanish from plasma radiation
spectrum (black line), and B ion line appears.
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
During boronization D:H ratio in peripheral plasma changed up to ~
1:4. When a valve for carborane injection was closed, from the plasma
radiation spectrum B line vanished, at the same time lines of impurities
have completely vanished. The carborane injection valve has been
opened at the most for 50 ms before the plasma shots start and start
time of its opening could be varied in a wide range.
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
The time dependencies of plasma current, plasma
density, of volts-seconds, hard X-rays detector along a
central chord for carborane container temperature 100°С
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
The time dependencies of plasma current, plasma
density, of volts-seconds, hard X-rays detector along a
central chord for carborane container temperature 50°С
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
Dependencies of a loop voltage before
and after boronization
SALAMANCA, SPAIN, 1-4 June, 2008
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Time dependence of the B line intensity at opening of an
injection valve for 50 ms before the plasma shot start
(black line) and for 75 ms after shot start (red line)
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
The time dependencies hydrogen into a chamber after
(red line) and during boronization (black line)
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
0
22673-BIII (60 C )
0
22691-BIII (100 C )
400000
Intensity (a.u.)
300000
200000
100000
0
50
100
150
200
Time (msec)
Time dependence of the B line intensity
for carborane container temperature
100°С (red line) and 60°С (black line)
SALAMANCA, SPAIN, 1-4 June, 2008
250
Troitsk Moscow reg., Russia
optic microscope x 1500
Images of the boron-carbon
film surface, SEM x 1400
optic microscope x 1500
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
coating images on the vacuum chamber T-11M
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
Conclusion
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Experiments on boronization in the tokamak T-11M plasma shots using
metacarborane were carried out.
Stabilization of a plasma column has improved, hydrogen recycling from
the vessel walls has decreased.
Plasma shot duration without disruption has essentially increased. At the
density of ne=1.3∙1013сm-3, Ip = 70кА a shot duration was ~350 ms and at
the density of ne=4.65∙1013сm-3, Ip = 70кА was ~ 250 ms, the hard X-rays
intensity in plasma shot and radiation losses have decreased, a plasma
lifetime has increased almost in four times.
High repeatability of experimental results has appeared.
The film with microhardness Н10 – 600 and the thickness up to 0,2 μm at
deposition rate of ~ 25 nm/s has been produced as a result of
boronization.
The impurities in wall areas were suppressed, high vacuum characteristics
of the discharge chamber have stabilized.
Presented technology opens the possibility of practical production of
renewable structured boron-carbon coating with use of plasma shots in
large-scale tokamaks, such as T-15M, ITER, DEMO.
SALAMANCA, SPAIN, 1-4 June, 2008
Troitsk Moscow reg., Russia
References
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[1] O.I. Buzhinskij, M.I. Guseva, G.V. Gordeeva, J. Nucl.
Mater. 196-175 (1990) 262
[2] L. Begrambekov, O. Buzhinskij, A. Gordeev, E. Miljaeva, P.
Leikin and P. Shigin, Physica Scripta, 108 (2004) 72.
[3] J. Winter, H.Esser, L. Konen, H.Reimer, L. Grobush, P.
Wienhold, J. Nucl. Mater. 162-164 (1989) 713.
[4] O.I. Buzhinskij and Yu.M. Semenets, Fusion Techn. 32 (1)
(1997) 1.
[5] O.I. Buzhinskij, V.G. Otroshchenko, D.G. Whyte, M.
Baldwin, R.W. Conn, R.P. Doerner, R. Seraydarian, S.
Luckhardt, H. Kugel, W.P. West, J. Nucl. Mater. 313-316 (2003)
214.
[6] V.A. Evtikhin, I.E. Lyublinski, A.V. Vertkov, S.V. Mirnov,
V.B.Lazarev, Proc. 16 IAEA Fusion Energy Conference, IAEA 3
(1997) 659.
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