In situ quantification of plasma facing surface Conditions in the Uragan-2M torsatron
The method and device has been developed and used for operative estimation of impurity level, outgassing rate and number of impurity gases molecular layers, on the surface of the Uragan-2M (U-2M) vacuum chamber walls. It is based on the thermal desorption of gases into a vacuum vessel from the sur...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2018
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| Цитувати: | In situ quantification of plasma facing surface Conditions in the Uragan-2M torsatron / G.P. Glazunov, D.I. Baron, M.N. Bondarenko, V.E. Moiseenko, I.E. Garkusha, A.L. Konotopskiy, A.V. Lozin, A.I. Lyssoivan, T. Wauters // Вопросы атомной науки и техники. — 2018. — № 6. — С. 12-16. — Бібліогр.: 11 назв. — англ. |
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irk-123456789-1488502019-02-19T01:26:22Z In situ quantification of plasma facing surface Conditions in the Uragan-2M torsatron Glazunov, G.P. Baron, D.I. Bondarenko, M.N. Moiseenko, V.E. Garkusha, I.E. Konotopskiy, A.L. Lozin, A.V. Lyssoivan, A.I. Wauters, T. Магнитное удержание The method and device has been developed and used for operative estimation of impurity level, outgassing rate and number of impurity gases molecular layers, on the surface of the Uragan-2M (U-2M) vacuum chamber walls. It is based on the thermal desorption of gases into a vacuum vessel from the surface of a special stainless steel probe during its heating up to temperature of 300ºC. The investigations were carried out of an outgassing rate and number of molecular layers on the probe surface in situ in the torsatron Uragan-2M. Decrease released gas amount from the surface by more than two orders of magnitude was recorded after Uragan-2M vacuum chamber VHF/RF discharge cleaning in various regimes and pumping. The method had been also tested in the regime of the measurements of hydrogen gas release retained in the probe before and after impact of RF plasma pulse discharges in work regime. Для оперативної оцінки кількості домішок на поверхні вакуумної камери торсатрона Ураган-2М використано метод, що грунтується на термодесорбції газів у вакуумі з поверхні зонда з нержавіючої сталі при його нагріві до температури 300ºС. Проведено дослідження газовиділення і оцінка числа моношарів домішок на поверхні зонда безпосередньо в торсатроні Ураган-2М. Після відкачування і чищення ВЧ/УКВ розрядами в різних режимах кількість домішок на поверхні знизилася більш ніж на два порядки. Метод випробувано також у режимі виміру швидкості виділення водню із зонда до і після дії плазми імпульсних ВЧ-розрядів у робочому режимі. Для оперативной оценки количества примесей на поверхности вакуумной камеры торсатрона Ураган-2М использован метод, основанный на термодесорбции газов в вакууме с поверхности зонда из нержавеющей стали при его нагреве до температуры 300ºС. Проведены исследования газовыделения и оценка числа монослоев примесей на поверхности зонда в непосредственно торсатроне Ураган-2М. После откачки и чистки ВЧ/УКВ разрядами в различных режимах количество примесей на поверхности снизилось более чем на два порядка. Метод испытан также в режиме измерения скорости выделения водорода из зонда до и после воздействия плазмы импульсных ВЧ-разрядов в рабочем режиме. 2018 Article In situ quantification of plasma facing surface Conditions in the Uragan-2M torsatron / G.P. Glazunov, D.I. Baron, M.N. Bondarenko, V.E. Moiseenko, I.E. Garkusha, A.L. Konotopskiy, A.V. Lozin, A.I. Lyssoivan, T. Wauters // Вопросы атомной науки и техники. — 2018. — № 6. — С. 12-16. — Бібліогр.: 11 назв. — англ. 1562-6016 PACS: 52.40.Hf http://dspace.nbuv.gov.ua/handle/123456789/148850 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| topic |
Магнитное удержание Магнитное удержание |
| spellingShingle |
Магнитное удержание Магнитное удержание Glazunov, G.P. Baron, D.I. Bondarenko, M.N. Moiseenko, V.E. Garkusha, I.E. Konotopskiy, A.L. Lozin, A.V. Lyssoivan, A.I. Wauters, T. In situ quantification of plasma facing surface Conditions in the Uragan-2M torsatron Вопросы атомной науки и техники |
| description |
The method and device has been developed and used for operative estimation of impurity level, outgassing rate and
number of impurity gases molecular layers, on the surface of the Uragan-2M (U-2M) vacuum chamber walls. It is based
on the thermal desorption of gases into a vacuum vessel from the surface of a special stainless steel probe during its
heating up to temperature of 300ºC. The investigations were carried out of an outgassing rate and number of molecular
layers on the probe surface in situ in the torsatron Uragan-2M. Decrease released gas amount from the surface by more
than two orders of magnitude was recorded after Uragan-2M vacuum chamber VHF/RF discharge cleaning in various
regimes and pumping. The method had been also tested in the regime of the measurements of hydrogen gas release
retained in the probe before and after impact of RF plasma pulse discharges in work regime. |
| format |
Article |
| author |
Glazunov, G.P. Baron, D.I. Bondarenko, M.N. Moiseenko, V.E. Garkusha, I.E. Konotopskiy, A.L. Lozin, A.V. Lyssoivan, A.I. Wauters, T. |
| author_facet |
Glazunov, G.P. Baron, D.I. Bondarenko, M.N. Moiseenko, V.E. Garkusha, I.E. Konotopskiy, A.L. Lozin, A.V. Lyssoivan, A.I. Wauters, T. |
| author_sort |
Glazunov, G.P. |
| title |
In situ quantification of plasma facing surface Conditions in the Uragan-2M torsatron |
| title_short |
In situ quantification of plasma facing surface Conditions in the Uragan-2M torsatron |
| title_full |
In situ quantification of plasma facing surface Conditions in the Uragan-2M torsatron |
| title_fullStr |
In situ quantification of plasma facing surface Conditions in the Uragan-2M torsatron |
| title_full_unstemmed |
In situ quantification of plasma facing surface Conditions in the Uragan-2M torsatron |
| title_sort |
in situ quantification of plasma facing surface conditions in the uragan-2m torsatron |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2018 |
| topic_facet |
Магнитное удержание |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/148850 |
| citation_txt |
In situ quantification of plasma facing surface Conditions in the Uragan-2M torsatron / G.P. Glazunov, D.I. Baron, M.N. Bondarenko, V.E. Moiseenko, I.E. Garkusha, A.L. Konotopskiy, A.V. Lozin, A.I. Lyssoivan, T. Wauters // Вопросы атомной науки и техники. — 2018. — № 6. — С. 12-16. — Бібліогр.: 11 назв. — англ. |
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Вопросы атомной науки и техники |
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ISSN 1562-6016. ВАНТ. 2018. №6(118)
12 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2018, № 6. Series: Plasma Physics (118), p. 12-16.
IN SITU QUANTIFICATION OF PLASMA FACING SURFACE
CONDITIONS IN THE URAGAN-2M TORSATRON
G.P. Glazunov, D.I. Baron, M.N. Bondarenko, V.E. Moiseenko, I.E. Garkusha,
A.L. Konotopskiy, A.V. Lozin, A.I. Lyssoivan*, T. Wauters*
National Science Center “Kharkov Institute of Physics and Technology”,
Institute of Plasma Physics, Kharkiv, Ukraine;
*Laboratory for Plasma Physics, ERM/KMS, Brussels, Belgium
The method and device has been developed and used for operative estimation of impurity level, outgassing rate and
number of impurity gases molecular layers, on the surface of the Uragan-2M (U-2M) vacuum chamber walls. It is based
on the thermal desorption of gases into a vacuum vessel from the surface of a special stainless steel probe during its
heating up to temperature of 300ºC. The investigations were carried out of an outgassing rate and number of molecular
layers on the probe surface in situ in the torsatron Uragan-2M. Decrease released gas amount from the surface by more
than two orders of magnitude was recorded after Uragan-2M vacuum chamber VHF/RF discharge cleaning in various
regimes and pumping. The method had been also tested in the regime of the measurements of hydrogen gas release
retained in the probe before and after impact of RF plasma pulse discharges in work regime.
PACS: 52.40.Hf
INTRODUCTION
In many cases during experiments or technological
processes in a high vacuum it is very important to know
not only such vacuum parameters as residual gas pressure
and partial impurity pressures in a volume of vacuum
chamber which usually are measured. The outgassing rate
of wall material, number of impurity molecular layers on
the wall surfaces are also important. In particular, the
latter essentially influences on the intensity of impurity
influx to plasma at the initial stage of plasma device
operation. For example, removing more than 100
molecules layers from the surfaces of the LHD stellarator
vacuum vessel (NIFS, Japan) due to ECR discharge
cleaning resulted in essential increase of plasma stored
energy.
In the case of the Uragan-2M (IPP, NSC KIPT,
Kharkov, Ukraine) the total number of gas molecules in
vacuum vessel with volume of 4 m3 at the pressure of
10-6 Torr is 1.4·1017. At the same time 100 impurity
molecular mono-layers on the surface of the U-2M
vacuum chamber contain more than 1022 molecules. That
means the measurements of residual pressure in a vacuum
volume don’t give the knowledge on real quantity of gas
molecules in it. To estimate the real amount of gas
molecules on the surface of vacuum chamber in situ one
can using the thermal desorption method. Such method
had been devised and preliminary tested in Ref. [1].
In present study the systematical measurements were
carried out of outgassing rate of the stainless steel probe,
and estimations were made of the number of molecules
layer on its surface in the U-2M torsatron after pulsed
VHF/RF wall conditioning procedure in different regimes.
Besides the impurity level, the hydrogen retention in the
vacuum chamber walls and its evolution during plasma
device operation can strongly influence on plasma
parameters. So the possibility to use such method for
investigations of hydrogen behavior, namely, hydrogen
gas outgassing and retention in stainless steel, in situ in
the U-2M torsatron was addressed too.
1. EXPERIMENTAL CONDITIONS
The scheme of the experiment and the photo of device
placed on the U-2M flange are shown in Fig. 1. The strip-
like probe (#2) was made of similar to U-2M vacuum
chamber (#1) material, i.e. stainless steel (SS)
12Kh18N10T, analogous to St316 steel. It was placed in
such a way to be flush with the U-2M wall. The probe
dimensions are 10 x 200 x 0.3 mm. Probe was connected
to the massive copper contacts (#3) of the electric power
supply (#6) providing pulsed heating of the probe to a
high temperature. The highest temperature of probe
heating used in this experimental series was 300ºС which
is sufficient to stimulate release of impurities from its
surface. At higher temperatures the gases, mainly
hydrogen, will start to release from the metal bulk. The
measured value was the pressure increase during probe
heating. Then, such characteristics were estimated as the
specific outgassing rate q (Torr·l/s·сm2 ) and the number
of molecules layers N on the probe surface.
Outgassing from the metal surface into a vacuum
volume could be divided on two sub-stages: at the rather
low temperatures up to 300°C, the gases adsorbed on the
metal surface, mainly H2O, CO, N2, CO2 release to the
vacuum volume. Namely investigations of this stage will
be presented in this paper first. When a metal temperature
increases to 350…700°С, others gases, mainly H2, are
emitted. The retained hydrogen atoms diffuse in the metal
bulk, they reach the surface and migrate along it, then
recombine, and desorb in the molecular form. If diffusion
is the most slow part of the process then the gas flow from
the metal obeys to the first Fick’s law, i.e., is proportional
to the gas concentration in the metal [2]. Situation would
be more complicated if the metal surface is not clean but
ISSN 1562-6016. ВАНТ. 2018. №6(118) 13
coated with films of matters with strong chemical bond,
e.g. oxides, carbides, etc. In this case Fick’s law can be
not valid and gas behavior may differ from the classic one
[3, 4], because other processes come to play, such as the
gas motion through the interface boundary, diffusion in
the films material, etc.
a
b
Fig. 1. The scheme of the experiment (a) and photo of
device (b): 1 – U-2M vacuum chamber wall; 2 – stainless
steel probe; 3 – current contacts; 4 – pressure gauge;
5 – time relay; 6 – electric power supply; 7 – VIT-2
vacuum measurement device; 8 – interface module
WAD-AIK-BUS; 9 – computer; 10 – branch pipe
Before SS probe placing in the U-2M chamber it was
calibrated on the heating voltage and specific outgassing
rate at the temperatures of 200…700ºС in the special
stand [5]. Outgassing behavior was investigated by means
of thermal desorption and mass-spectrometry methods
similar to described in the paper [6]. The SS probe
temperature was measured by a W-Re thermocouple
attached into the probe centre. It is necessary to note, that
in this case the measurements were carried out in
stationary regimes of heating. The specific net outgassing
rate (q) was calculated from the equation
q = (P-P0)S/F, (1)
where S=100 l/s was the pumping speed, and F28 cm2
was the area of the heated to 250…300ºC probe surface.
The estimated value of the specific outgassing rate of the
SS probe in the temperature range 250…300ºC was
determined as 8·10-5 Torrls-1cm-2 and was used to
estimate q and N values measured in the U-2M, when the
pulsed regime of probe heating was used. The 5 V applied
voltage during 4 seconds is sufficient to provide probe
heating to the temperature of 250…300ºC.
2. RESULTS, DISCUSSION
Then the probe has been placed in the Uragan-2M
branch pipe (see #10 in Fig. 1,b). It is used without the
thermocouple to provide minimum parasitic outgassing.
U-2M vacuum chamber was pumped to the pressure of
~10-6 Torr by the fore-pump and three turbo molecular
pumps, each with the net pumping speed 0.5 m3/s. Then
the SS probe measurements are used and the heating time
is established as 4 s at the 5 V of applied voltage. The probe
temperature increased up to 300ºC and the pressure increase
in the branch pipe #10 ( see Fig. 1) caused by desorbed gases
was measured.
The measurements of the SS outgassing rate and
number of monolayer estimations were carried out after
such a wall conditioning daily procedure: 1.5…2 hours
VHF/RF steady state or pulsed discharge cleaning
(standard VHF and RF regimes of discharges cleaning
were described in [7-9]) in atmosphere of H2, N2, gases,
and their mixture, then pumping during 1.5…2 hours with
3 turbo molecular pumps, then 1.5..2.5 hours VHF/RF
pulsed discharge cleaning again and long time pumping
during 18 hours with three turbo molecular pumps. The
VHF steady state discharge characteristics were: VHF
(f=140 MHz) generator power was about 3 kW and
applied to Т-like antenna both in regime with magnetic
field and without. The pressure of working gas during
regime without magnetic field was 2·10-2 Torr , and in the
regime with low magnetic field (~ 0.01 T) it was 1·10-4 Torr.
During RF pulse discharge cleaning regime, two RF-
generators with power about 50 kW of each operated at
low magnetic field (up to 0.01 T). Power of the one
generator (f=5 МHz) applied to the frame antenna. Second
generator power (4.8 MHz) applied to the three-half-turn
antenna. Pulse duration was 20 ms and the pulse repetition
rate was 4 pulses/min.
The typical apparatus curves of pressure temporal
behavior are shown in Figs. 2, 3. The small signal in Fig. 3
measured 1 min later after switch off the first pulsed
heating, corresponds to less than one monolayer and it
means that practically all gases adsorbed on the probe
surface had been desorbed during first thermal pulse.
Note, that the time of formation of one monolayer on the
surface at room temperature in vacuum conditions of
10-6 Torr is only about 5 seconds [10].
Fig. 2. Apparatus curve of pressure increase in the
Uragan-2M during SS probe heating to the
temperature of 300ºС: t1 and t2 are the times of switch on
and switch off the heating, initial pressure
is 1.18·10-6 Torr
14 ISSN 1562-6016. ВАНТ. 2018. №6(118)
The specific outgassing rate was estimated from the
above mentioned equation (1).
The estimation of monolayer number on the probe
surface was carried out with the use of the equation:
N=V·L/N, (2)
where V (normal сm3)= qt – the amount of the gas
desorbed from the unitary probe surface; t (s) – time of
the gas desorption; L – number of molecules in the gas
volume of the 1 cm3 (Loshmidt’s number); Nw – the
number of molecules in the monolayer on the unitary
surface. In the calculations it was supposed the water
vapor as the main adsorbed substance and, according to
Ref. [11] data, Nw 5·1014 сm-2. In fact, the mass-
spectrometric measurements made during SS probe
heating to 300ºC temperature in the U-2M-vacuum
chamber and also measurements in the above mentioned
special stand confirmed this assumption. Noticeable
increasing of desorbed CO2 (44 u), 28 u and hydrocarbons
(58 u) was observed, too.
Fig. 3. Apparatus curve of pressure increase in the U-2M
during SS probe heating to the temperature of 300ºС after
1 minute of the first pulsed heating: t1 and t2 are the times
of switch on and switch off the heating
Numerical calculation is applied to the measurement
displayed in Fig. 2. The analysis is based on the gas
balance equation:
d(pV)/dt = Q- pS, (3)
where Q is cumulate outgassing (Torrl/s). In the equation,
the vacuum vessel V volume and the pumping speed S are
assumed to be constant. The outgassing and the pressure
could be split into two parts Q=Q0+Qp and p=p0+pp,
where Q0 and p0 are the stationary solutions of Eq. (3),
and Qp and pp are probe induced variations (non-
stationary). As it is seen from Fig. 3, after heat pulse to
the probe the pressure decreases with the characteristic
time td~10 s. However, it does not return to the initial
value. The residual pressure pp*=pp-pg starting certain
time after heat pulse should obey Eq. (1) with zero
outgassing term. In this case the equation has an analytical
solution
pp*=p1exp[(t-t1)/t0], (4)
where t1 is an arbitrary time moment. The result of
numerical fitting of analytical solution to the experimental
curve is shown in Fig. 4.
The fact that fitting is successful could be explained by
domination of one gas sort in the released gas mixture.
Fitting gives the value of t0=V/S=9.4 s. The corresponding
pumping speed is S=420 l/s. Knowing pumping speed, the
cumulate outgassing is calculated using Eq. (3) Fig. 5.
The above described procedure of measurements and
simplified data processing is applied to the different
conditions in the U-2M vacuum chamber that gives the
dynamics of decreasing of outgassing rate from the
vacuum chamber walls and number of molecules layers
during U-2M chamber wall conditioning (Fig. 6).
Fig. 4. Pressure curve from Fig. 3 (solid line) and fitted
analytical curve (dashed line)
Fig. 5. Cumulate outgassing calculated for the
measurement displayed in Fig. 7
Fig. 6. Uragan-2M wall conditions: green points
correspond to number of molecular layers on the surface
of SS probe; red rhombs correspond to SS probe
outgassing rate at 300ºC after VHF or RF discharge
cleaning and pumping
The figure reflects, in general, positive wall
conditioning tendency with different rates for different
wall conditioning scenarios. It is seen in Fig. 6 (points
21…36) that steady state VHF discharge cleaning in low
(0.01…0.02 T) magnetic field is more effective than the
regime without magnetic field (points 1…17). In turn, the
RF pulse discharge wall conditioning in these conditions
seems more effective than the VHF (points 52…82). The
ISSN 1562-6016. ВАНТ. 2018. №6(118) 15
number of molecules layers was decreased up to less than
one layer for both VHF and RF discharge cleaning. Drastic
increase of the outgassing rate in the point 56 is caused by
pumping void during 16 days. In this time the U-2M
vacuum chamber was filled with nitrogen at the
atmosphere pressure.
Note, if to measure the SS probe outgassing just after
the short time RF/VHF discharge cleaning, the SS
outgassing rates are essentially, in about one order of
magnitude higher, as it is seen in Fig. 7.
It is the evidence that very high impurity flow desorbs
under plasma-surface interactions and that the pumping
facilities do not cope with impurity pumping. As the result
these impurities redeposit on the walls of the vacuum
chamber and branch pipes after finishing of the discharge
cleaning. The subsequent pumping of the U-2M vacuum
chamber during 18 hours leads to obtaining rather high
vacuum with 7·10-7 Torr pressure and to decreasing of the
number of molecules layers on the SS probe surface up to
N=0.5…1 instead of N~100 at the pressure of ~7·10-6 Torr
at the beginning of the wall discharge cleaning campaign.
U-2M wall conditions
1,E-06
1,E-05
1,E-04
1,E-03
1 2 3 4
Number of measurement
S
p
e
c
if
ic
o
u
tg
a
s
s
in
g
ra
te
,
T
o
rr
.l
/s
.c
m
2
0,1
1
10
100
N
u
m
b
e
r
o
f
m
o
le
c
u
le
s
la
y
e
rs
number of molecules layers
Specific outgassing rate
Fig. 7. U-2M wall conditions in different times of
measurements: points with index 1 (RF) and 3 (VHF)
were measured for standard procedure of discharge
cleaning just after 18 hours pumping; points 2 and 4 were
obtained one hour shortly after the discharge cleaning
end both for the VHF(2) or RF(4)
Finally, some words on the possibility to use such
methods for hydrogen behavior (retention and release
from stainless steel) investigations in situ in the U-2M
torsatron. The effective hydrogen diffusion and desorption
starts at the temperatures above 350°C. If after the SS
probe heating to the temperature of 300°C to heat it once
more, but to the temperature of 500°C (by increasing of
voltage or time of electric pulse), the hydrogen atoms in
the metal bulk will diffuse to the surface, where recombine
into molecules and then will desorb.
It is shown in Fig. 8 hydrogen release from the SS
probe during its heating to temperatures of 500…700°C.
The measurement at 500ºC temperature (green point 1)
was carried out after standard cycle of discharge cleaning:
1.5…2 hours RF pulsed discharge cleaning in H2, then
pumping during 1.5…2 hours, then 1.5…2.5 hours RF
pulsed discharge cleaning and long time pumping during
18 hours. After hydrogen release measurement the
operation regime switched to the following: RF power
from two generators was applied to two antennas. One of
them (f = 4.8 MHz, 50 kW) was launched to the frame
antenna and the second one (f = 5 MHz, 120 kW) was
connected to three half-turn antenna. The pressure of
working gas (hydrogen) was within the range 6·10 -6 Torr
to 2·10-5 Torr, the magnetic field was ~0.36 T. Plasma
pulses duration was 5…25 ms, in series of one pulse per
2 min. After two hours work in such a regime, it was
switched off and U-2M vacuum chamber was pumped to
the pressure of about (1…2)·10-6 Torr. Then the
measurement of hydrogen release from the SS probe was
carried out at the same 500ºC temperature (green point 2,
Fig. 7). It is seen that hydrogen release rate increased in
more than one order. Then a few high heating pulses (5 V,
10 s, brown points in Fig. 8) were applied to the probe to
remove hydrogen from the probe bulk. Pulses off-duty
time was two minutes.
1.E-06
1.E-05
1.E-04
1.E-03
1 2 3 4 5 6 7
Number of measurement
H
y
d
ro
g
e
n
r
e
le
a
s
e
r
a
te
,
T
o
rr
.l
/s
.c
m
2
Fig. 8. Hydrogen release from the SS probe: green
color – sample temperature under the measurement was
500ºC; brown color – sample temperature under the
measurement was 600…700ºC
From pulse to pulse the SS probe temperature
increased from 600°C (first pulse) to 700°C (fourth pulse).
Then, after the probe cooling down to the room
temperature, the measurement of hydrogen release rate at
the temperature of 500°C was carried out (point seven in
Fig. 7).
It is seen that after four high heating pulses hydrogen
gas release (hydrogen outgassing rate) decreased in about
four times. So, using proposed method one can effectively
monitor not only the surface conditions but hydrogen
retention with the vacuum chamber wall material, too.
Note, not only hydrogen particles in different states
impact on the U-2M wall surface. It may be nitrogen,
oxygen, carbon, etc. Study of recycling process for those
is also important. In general case this is of a great interest
not only for fusion device but for different plasma
installations, e.g., plasma accelerators, devices for
vacuum-plasma or magnetron deposition, glow discharge
plasma facilities etc.
SUMMARY AND CONCLUSIONS
Using thermal desorption method the investigations
were carried out of the wall conditions, outgassing rate
and estimation of the number of molecules layers, in the
Uragan-2M torsatron in situ after discharge cleaning in
different regimes and pumping. It had been indicated that
the VHF and RF discharge cleaning in low magnetic
fields of 0.01…0.02 T is more effective than the regimes
16 ISSN 1562-6016. ВАНТ. 2018. №6(118)
without magnetic field. After preliminary short time
VHF/RF discharge cleaning and long time pumping the
number of impurity molecules layers was decreased from
100 up to less than one layer. The analysis of the obtained
data allows saying that such method could be used to
monitor the quality of wall conditioning processes during
preparing to plasma experiments.
The proposed method was tested in the high
temperature regime (400…700ºC) to measure hydrogen
outgassing from the SS probe. It was observed the
essential (one order of magnitude) increase of hydrogen
outgassing after two hours exposure by plasma discharge
in working regime. It means that hydrogen concentration
in the SS probe also increased.
It is necessary to note, that using thermal desorption
probe method one can effectively monitor not only surface
conditions but hydrogen retention in the vacuum chamber
wall material, too.
ACKNOWLEDGEMENTS
This work has been carried out within the framework
of the EUROfusion Consortium and has received funding
from the Euratom research and training programme 2014-
2018 under grant agreement № 633053. The views and
opinions expressed herein do not necessarily reflect those
of the European Commission.
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Article received 10.10.2018
IN SITU КОЛИЧЕСТВЕННЫЙ АНАЛИЗ УСЛОВИЙ НА ПОВЕРХНОСТИ СТЕНОК ВАКУУМНОЙ
КАМЕРЫ ТОРСАТРОНА УРАГАН-2М
Г.П. Глазунов, Д.И. Барон, М.Н. Бондаренко, В.Е. Моисеенко, И.Е. Гаркуша, А.Л. Конотопский, А.В. Лозин,
А.И. Лысойван, Т. Wauters
Для оперативной оценки количества примесей на поверхности вакуумной камеры торсатрона Ураган-2М
использован метод, основанный на термодесорбции газов в вакууме с поверхности зонда из нержавеющей стали
при его нагреве до температуры 300С. Проведены исследования газовыделения и оценка числа монослоев
примесей на поверхности зонда в непосредственно торсатроне Ураган-2М. После откачки и чистки ВЧ/УКВ
разрядами в различных режимах количество примесей на поверхности снизилось более чем на два порядка.
Метод испытан также в режиме измерения скорости выделения водорода из зонда до и после воздействия
плазмы импульсных ВЧ-разрядов в рабочем режиме.
IN SITU КІЛЬКІСНИЙ АНАЛІЗ УМОВ НА ПОВЕРХНІ СТІНОК ВАКУУМНОЇ КАМЕРИ
ТОРСАТРОНА УРАГАН-2М
Г.П. Глазунов, Д.І. Барон, М.М. Бондаренко, В.Є. Моiсеєнко, І.Є. Гаркуша, О.Л. Конотопський, О.В. Лозiн,
А.И. Лисойван, Т. Wauters
Для оперативної оцінки кількості домішок на поверхні вакуумної камери торсатрона Ураган-2М використано
метод, що грунтується на термодесорбції газів у вакуумі з поверхні зонда з нержавіючої сталі при його нагріві
до температури 300С. Проведено дослідження газовиділення і оцінка числа моношарів домішок на поверхні
зонда безпосередньо в торсатроні Ураган-2М. Після відкачування і чищення ВЧ/УКВ розрядами в різних
режимах кількість домішок на поверхні знизилася більш ніж на два порядки. Метод випробувано також у
режимі виміру швидкості виділення водню із зонда до і після дії плазми імпульсних ВЧ-розрядів у робочому
режимі.
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