Damaging of pure tungsten with different microstructure under sequential QSPA and LHD plasma loads
The cracking thresholds were evaluated for tungsten samples with different microstructure in the course of QSPA Kh – 50 repetitive plasma loads. No damage has been observed on the exposed surfaces under 0.1 MJ/m². Nevertheless, cracks were detected in the bulk of irradiated tungsten (with longitudin...
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| Zitieren: | Damaging of pure tungsten with different microstructure under sequential QSPA and LHD plasma loads / S.S. Herashchenko, O.V. Byrka, V.A. Makhlaj, M. Wirtz, N.N. Aksenov, I.E. Garkusha, Yu.V. Petrov, S.V. Malykhin, S.V. Surovitskiy, S. Masuzaki, M. Tokitani, S.I. Lebedev, P.B. Shevchuk // Problems of atomic science and tecnology. — 2020. — № 6. — С. 78-82. — Бібліогр.: 17 назв. — англ. |
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irk-123456789-1946482023-11-28T12:43:00Z Damaging of pure tungsten with different microstructure under sequential QSPA and LHD plasma loads Herashchenko, S.S. Byrka, O.V. Makhlaj, V.A. Wirtz, M. Aksenov, N.N. Garkusha, I.E. Petrov, Yu.V. Malykhin, S.V. Surovitskiy, S.V. Masuzaki, S. Tokitani, M. Lebedev, S.I. Shevchuk, P.B. Plasma dynamics and plasma-wall interaction The cracking thresholds were evaluated for tungsten samples with different microstructure in the course of QSPA Kh – 50 repetitive plasma loads. No damage has been observed on the exposed surfaces under 0.1 MJ/m². Nevertheless, cracks were detected in the bulk of irradiated tungsten (with longitudinal grain orientation). Increasing heat load up to 0.2 MJ/m² caused the damaging of all types of tungsten targets. The observed cracks propagate to the bulk mainly transversely and parallel to the irradiated surface. The effect of the subsequent exposure with LHD divertor plasma on the tungsten samples was analyzed. The obtained results are discussed. Було оцінено пороги розтріскування для зразків вольфраму з різною мікроструктурою в процесі повторюваних плазмових навантажень КСПП Х–50. При навантаженнях менше 0,1 МДж/м², на відкритих поверхнях зразків вольфраму ушкоджень не спостерігається. Проте, тріщини спостерігаються в обсязі опроміненого зразка вольфраму з поздовжньою орієнтацією зерен. Підвищення теплового навантаження до 0,2 МДж/м² призводить до пошкодження всіх типів вольфрамових мішеней. Тріщини поширюються в обсязі в основному поперечно і паралельно до опромінюваної поверхні. Проаналізовано вплив діверторної плазми LHD на поверхню зразків вольфраму. Порівнюються результати впливу на зразки вольфраму з різною мікроструктурою. Были оценены пороги растрескивания для образцов вольфрама с различной микроструктурой в процессе повторяющихся плазменных нагрузок КСПУ Х–50. При нагрузках менее 0,1 МДж/м² на открытых поверхностях образцов вольфрама повреждений не наблюдается. Тем не менее трещины наблюдаются в объеме облученного образца вольфрама с продольной ориентацией зерен. Повышение тепловой нагрузки до 0,2 МДж/м² приводит к повреждению всех типов вольфрамовых мишеней. Наблюдаемые трещины распространяются в объеме в основном поперечно и параллельно облучаемой поверхности. Проанализировано влияние диверторной плазмы LHD на поверхность образцов вольфрама. Сравниваются результаты воздействия на образцы вольфрама с различной микроструктурой. 2020 Article Damaging of pure tungsten with different microstructure under sequential QSPA and LHD plasma loads / S.S. Herashchenko, O.V. Byrka, V.A. Makhlaj, M. Wirtz, N.N. Aksenov, I.E. Garkusha, Yu.V. Petrov, S.V. Malykhin, S.V. Surovitskiy, S. Masuzaki, M. Tokitani, S.I. Lebedev, P.B. Shevchuk // Problems of atomic science and tecnology. — 2020. — № 6. — С. 78-82. — Бібліогр.: 17 назв. — англ. 1562-6016 PACS: 52.40.Hf http://dspace.nbuv.gov.ua/handle/123456789/194648 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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| language |
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Plasma dynamics and plasma-wall interaction Plasma dynamics and plasma-wall interaction |
| spellingShingle |
Plasma dynamics and plasma-wall interaction Plasma dynamics and plasma-wall interaction Herashchenko, S.S. Byrka, O.V. Makhlaj, V.A. Wirtz, M. Aksenov, N.N. Garkusha, I.E. Petrov, Yu.V. Malykhin, S.V. Surovitskiy, S.V. Masuzaki, S. Tokitani, M. Lebedev, S.I. Shevchuk, P.B. Damaging of pure tungsten with different microstructure under sequential QSPA and LHD plasma loads Вопросы атомной науки и техники |
| description |
The cracking thresholds were evaluated for tungsten samples with different microstructure in the course of QSPA Kh – 50 repetitive plasma loads. No damage has been observed on the exposed surfaces under 0.1 MJ/m². Nevertheless, cracks were detected in the bulk of irradiated tungsten (with longitudinal grain orientation). Increasing heat load up to 0.2 MJ/m² caused the damaging of all types of tungsten targets. The observed cracks propagate to the bulk mainly transversely and parallel to the irradiated surface. The effect of the subsequent exposure with LHD divertor plasma on the tungsten samples was analyzed. The obtained results are discussed. |
| format |
Article |
| author |
Herashchenko, S.S. Byrka, O.V. Makhlaj, V.A. Wirtz, M. Aksenov, N.N. Garkusha, I.E. Petrov, Yu.V. Malykhin, S.V. Surovitskiy, S.V. Masuzaki, S. Tokitani, M. Lebedev, S.I. Shevchuk, P.B. |
| author_facet |
Herashchenko, S.S. Byrka, O.V. Makhlaj, V.A. Wirtz, M. Aksenov, N.N. Garkusha, I.E. Petrov, Yu.V. Malykhin, S.V. Surovitskiy, S.V. Masuzaki, S. Tokitani, M. Lebedev, S.I. Shevchuk, P.B. |
| author_sort |
Herashchenko, S.S. |
| title |
Damaging of pure tungsten with different microstructure under sequential QSPA and LHD plasma loads |
| title_short |
Damaging of pure tungsten with different microstructure under sequential QSPA and LHD plasma loads |
| title_full |
Damaging of pure tungsten with different microstructure under sequential QSPA and LHD plasma loads |
| title_fullStr |
Damaging of pure tungsten with different microstructure under sequential QSPA and LHD plasma loads |
| title_full_unstemmed |
Damaging of pure tungsten with different microstructure under sequential QSPA and LHD plasma loads |
| title_sort |
damaging of pure tungsten with different microstructure under sequential qspa and lhd plasma loads |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2020 |
| topic_facet |
Plasma dynamics and plasma-wall interaction |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/194648 |
| citation_txt |
Damaging of pure tungsten with different microstructure under sequential QSPA and LHD plasma loads / S.S. Herashchenko, O.V. Byrka, V.A. Makhlaj, M. Wirtz, N.N. Aksenov, I.E. Garkusha, Yu.V. Petrov, S.V. Malykhin, S.V. Surovitskiy, S. Masuzaki, M. Tokitani, S.I. Lebedev, P.B. Shevchuk // Problems of atomic science and tecnology. — 2020. — № 6. — С. 78-82. — Бібліогр.: 17 назв. — англ. |
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Вопросы атомной науки и техники |
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ISSN 1562-6016. ВАНТ. 2020. №6(130)
78 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2020, № 6. Series: Plasma Physics (26), p. 78-82.
https://doi.org/10.46813/2020-130-078
DAMAGING OF PURE TUNGSTEN WITH DIFFERENT
MICROSTRUCTURE UNDER SEQUENTIAL QSPA AND LHD
PLASMA LOADS
S.S. Herashchenko
1,2
, O.V. Byrka
1
, V.A. Makhlaj
1,2
, M. Wirtz
3
, N.N. Aksenov
1
,
I.E. Garkusha
1,2
, Yu.V. Petrov
1
, S.V. Malykhin
4
, S.V. Surovitskiy
4
, S. Masuzaki
5
, M. Tokitani
5
,
S.I. Lebedev
1
, P.B. Shevchuk
1
1
Institute of Plasma Physics NSC “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine;
2
V.N. Karazin Kharkiv National University, Kharkiv, Ukraine;
3
Forschungszentrum Julich, EURATOM Association, Julich, Germany;
4
National Technical University “Kharkiv Polytechnic Institute”, Kharkiv, Ukraine;
5
National Institute for Fusion Science, Oroshi 322-6, Toki 509-5292 JAPAN
E-mail: gerashchenko@kipt.kharkov.ua
The cracking thresholds were evaluated for tungsten samples with different microstructure in the course of
QSPA Kh-50 repetitive plasma loads. No damage has been observed on the exposed surfaces under 0.1 MJ/m
2
.
Nevertheless, cracks were detected in the bulk of irradiated tungsten (with longitudinal grain orientation). Increasing
heat load up to 0.2 MJ/m
2
caused the damaging of all types of tungsten targets. The observed cracks propagate to the
bulk mainly transversely and parallel to the irradiated surface. The effect of the subsequent exposure with LHD
divertor plasma on the tungsten samples was analyzed. The obtained results are discussed.
PACS: 52.40.Hf
INTRODUCTION
Tungsten is now considered as a primary material
for the armor of plasma facing components in the
divertor region of fusion devices like ITER and DEMO.
The development of advanced tungsten grades requires
thorough testing and qualification of material in extreme
fusion relevant conditions, including both high heat and
particle fluxes (H isotopes, He and neutron) [1, 2].
Experimental simulations of high-energy fluxes
expected in fusion reactors are carried out in presently
available fusion devices such as ASDEX Upgrade, JET
or Large Helical Device (LHD) [1, 3]. Furthermore,
simulation experiments are also performed using linear
and e-beam facilities, pulsed plasma guns, powerful
quasi-stationary plasma accelerators (QSPA) as test-bed
facilities [4-13].
For pure tungsten as well as for tungsten-based
composites the surface cracking has been extensively
studied within the linear plasma devices and e-beam
facilities [11-13]. The obtained results showed different
kinds of damage appeared depending on the loading
sequence, power density, microstructure of the samples,
and their base temperature. W samples with transversal
grain orientation exhibited the weakest damage
resistance and the increase of their base temperature
could not compensate for the detrimental impact of
deuterium. It is shown that transient heat load led to the
appearance of surface crack meshes, while consecutive
steady-state load induced tensile stresses and opened
existing surface cracks [13].
Incident helium ions might also have a strong impact
on the surface evolution, with the formation of
dislocation loops and bubbles [1, 12]. These changes at
the material surface might promote the hydrogen
retention in the structure, which is one of the major
concerns for next generation devices. Therefore,
understanding of the microstructure changes and its
consequences are of primary importance. Microscopic
damage and helium depth profiles in metals bombarded
by helium atoms have been studied during LHD helium
discharges. From TEM observations, a considerable
amount of dislocation loops and helium bubbles of
about 1…2 nm size are identified [3, 14].
The observation of micro-crack networks in
experiments involving QSPA Kh-50 was attributed to
the surface melting and subsequent re-solidification [5,
15]. It was found that due to the material degradation.
the increasing number of repetitive exposures shifts
down the energy threshold for the crack onset up to 50
percent [15-17]. Even the loads, which are twice less
than the melting energy threshold led to the appearance
of fatigue cracks already after 100 plasma pulses. In this
case, the cracks initiation could be caused by an
accumulation of the stress-induced lattice defects which
harden the material in plasma-affected thin sub-surface
layer [7-9]. Analysis of experimental data confirms that
the origin of crack formation could be attributed to the
plastic deformation of surface layers by the twinning
mechanism. The twinning mechanism is reinforced by
the interaction of twins with hydrogen-filled micro-
pores [8, 9].
Thus, experiments with sequential transient and
stationary heat loads have shown quite a strong
influence of combined impact on plasma facing
materials. Therefore, further evaluation of damaging
thresholds for tungsten in conditions of combined heat
loads relevant to fusion reactor is necessary. This paper
presents the first results on sequential moderate pulsed
plasma loads from the QSPA Kh-50 plasma accelerator
mailto:gerashchenko@kipt.kharkov.ua
ISSN 1562-6016. ВАНТ. 2020. №6(130) 79
and following exposures of as-received and pretreated
samples by ions and charge-exchange particles within
the divertor fluxes in the Large Helical Device.
1. EXPERIMENTAL SETUP AND
DIAGNOSTICS
Plasma-heat load tests of tungsten with energy
density, pulse duration and particle loads relevant to
ITER transient events have been carried out in a
QSPA Kh-50 quasi-stationary plasma accelerator [5, 6].
Samples of pure tungsten with the longitudinal (L) and
transversal (T) grain orientation and in the recrystallized
(R) state were used for the experiments [13]. Samples
have sizes of (12 × 12 × 5) mm
3
. All specimens were
polished to achieve a mirror-like surface. The samples
were supplied by Plansee AG, prepared and delivered
from Forschungszentrum Julich.
The main parameters of the QSPA Kh-50 plasma
streams were as follows: ion impact energy ~ 0.4 keV;
maximum plasma pressure up to 0.32 MPa; the plasma
stream diameter 18 cm. The plasma pulse shape is
triangular with pulse duration of 0.25 ms [15]. The heat
loads onto the exposed surfaces were selected to be
rather moderate: 0.1 MJ∙×m
-2
(heat flux factor
FHF≈6.3 MW∙s
0.5
∙m
-2
) and 0.2 MJ∙m
-2
(FHF≈12.7 MW∙s
0.5
∙m
-2
) to operate below the tungsten
cracking threshold for a small number of plasma pulses
[15]. Before each plasma pulse, the surface temperature
(Tbase) of one series of tungsten targets was kept near
room temperature (RT). The second series of the
samples was preheated before the exposures to Tbase=
400°C with a special heater [5, 16]. The maximum
number of irradiation plasma pulses was 200.
The induced damages have been analyzed by SEM
and laser profilometry after 100 and 200 the QSPA
pulses. Subsequently, the cross sections of the samples
have been investigated by metallographic means to
analyze the crack propagation into the bulk material.
As the second step, an irradiation of both pre-loaded
and original W targets was performed by deuterium
plasma fluxes (average ion flux of 3.7·10
23
m
-2
∙s
-1
, heat flux
of ≤ 10 MW/m
2
) at the divertor region within Large
Helical Device (LHD) at the National Institute of Fusion
Science [3, 14]. The samples were exposed to the
divertor plasma fluxes for 2 s. Subsequently the
irradiated samples were analyzed using SEM+EDS, and
TEM (transmission electron microscopy).
2. EXPERIMENTAL RESULTS
2.1. TUNGSTEN SAMPLES EXPOSED WITH
HEAT LOAD TO 0.1 MJ/m
2
Samples of pure tungsten (longitudinal (L) and
transversal (T) grain orientation and in the recrystallized
state (R)) were exposed to 100 and 200 QSPA plasma
pulses with heat load 0.1 MJ∙m
-2
(heat flux factor
FHF ≈ 6.3 MW∙s
0.5
∙m
-2
).
Plasma irradiation after 100 QSPA pulses with a
surface heat load of 0.1 MJ/m
2
does not cause damages
on the exposed surfaces of all tungsten samples
independently on their microstructure (Fig. 1). Only
slightly increasing surface roughness is observed
(Ra ≤ 1.2 µm). The metallographic analysis shows the
cracks penetration to the bulk of exposed tungsten
sample with longitudinal orientation (Fig. 2). The cracks
propagate to the material in parallel to the sample
surface. The maximum crack depth is about 200 µm.
Fig. 1. SEM image of L sample surface exposed with the
QSPA plasma load of 0.1 MJ/m
2
at Tbase = 400°C
Fig. 2. Optical microscope image of the crack
penetration in the metallographic cross section of L
sample exposed with the plasma load of 0.1 MJ/m
2
at
Tbase = 400°C
Fig. 3. SEM image of R sample surface after the QSPA
exposure with heat load of 0.2 MJ/m
2
at Tbase = RT
An increasing number of QSPA plasma exposures
up to 200 pulses does not significantly affect the
80 ISSN 1562-6016. ВАНТ. 2020. №6(130)
samples’ surface morphology. The metallographic
analysis results are completely identical in both cases.
Fig. 4. Light microscope image of the metallographic
cross section of R sample irradiated by the QSPA
plasma load of 0.2 MJ/m
2
at Tbase = RT
a
b
c
Fig. 5. SEM image of surface of T (a), L (b) and R (c)
sample after the QSPA exposure with heat load of 0.2
MJ/m
2
at Tbase = 400°C
2.2. TUNGSTEN SAMPLES EXPOSED
TO 0.2 MJ/m
2
Increasing heat load up to 0.2 MJ/m
2
causes surface
damage appearance for all types of tungsten targets. A
large number of repetitive plasma loads
(FHF ≈ 12.7 MW×s
0.5
×m
-2
) leads to surface modification
and cracks appearing on affected surfaces.
a
b
c
Fig. 6. Light microscope image of the metallographic
cross section of T (a), L (b) and R (c) sample after the
QSPA exposure with heat load of 0.2 MJ/m
2
at Tbase = 400°C
A rather significant difference has been observed in
the morphology of tungsten samples that exposed at
room temperature. Metallographic analysis for the
recrystallized tungsten sample showed the formation of
a network of cracks on the surface (Fig. 3). Crack
propagation to the bulk along the grains boundaries is
also observed at depths up to 150 µm (Fig. 4). For W
samples with the longitudinal and transversal grain
orientation, there were still no damages detected.
Small cracks were appeared on the surfaces of
exposed tungsten samples pre-heated to 400°C (Fig. 5).
The length of the cracks is varied from 30 to 80 μm.
Increasing surface roughness is observed for all samples
too.
For tungsten samples with transversal grain
orientation, single cracks propagate normally to the
ISSN 1562-6016. ВАНТ. 2020. №6(130) 81
surface. They are observed in the near-surface layer at
depth of up to 50 µm (Fig. 6,a).
Features of the pre-heated L tungsten samples need
to be discussed in more detail. As it is seen from the
metallographic cross section (Figs. 2, 6,b), QSPA
exposures with heat load of 0.1 MJ/m
2
and 0.2 MJ/m
2
lead to crack propagation in the near-surface layer
parallel to the surface. Deep cracks are longer (˃ 1mm)
in both cases. The maximum depth of cracks was almost
200 μm for the heat load of 0.1 and 600 μm for
0.2 MJ/m
2
. All cracks originate in the near-surface layer
and further grow far into depth. Cracks change their
orientation during propagation deviating from their
initial path.
Fig. 7. SEM image of surface of R sample after the
QSPA exposure and plasma fluxes in divertor
region of LHD
2.3. TUNGSTEN SAMPLES EXPOSED TO THE
LHD DIVERTOR PLASMA
Three types of tungsten samples (T, L, R) were
further exposed to plasma fluxes in the divertor region
of LHD both in as-received state and after the pulsed
QSPA plasma loads (200 pulses of 0.1 MJ/m
2
) aiming at
analysis of possible effects from combined exposures.
Fig. 8. TEM probe of R sample surface exposed to
both QSPA plasma and divertor fluxes in LHD
The LHD divertor plasma exposures do not revealed
any synergistic effects on the surfaces of the samples.
Generally, no differences are observed on the surfaces
between initial samples and ones irradiated by the
QSPA Kh-50.
Analysis of the surface morphology of the tungsten
samples indicates the absence of any extra damages.
The grains’ boundaries are clearly visible (Fig. 7).
After plasma exposures, microstructures of samples
were observed by means of TEM. Fig. 8 presents the
TEM probe from the R sample after the consecutive
combination of the QSPA exposure and plasma fluxes
in the LHD divertor.
It should be noted that LHD divertor fluxes resulted
in surface modification and formation of a sub-surface
layer of approximately 10 nm thickness for all exposed
samples. In this layer, so-called bubbles are routinely
observed (Fig. 9). Taking into account the sizes of
bubbles, these bubbles look to be attributed to
deuterium and helium bombardment effects within
LHD.
Fig. 9. TEM image of the cross section of R tungsten
sample after the QSPA exposure and divertor plasma
fluxes in LHD
CONCLUSIONS
Experimental studies of the damage features for pure
tungsten with different microstructure under the
moderate plasma loads have been performed with a
quasi-stationary plasma accelerator QSPA Kh-50. The
heat loads on the surface were below the cracking
threshold (for virgin material). The number of plasma
pulses was 100 and 200.
The repetitive plasma loads lead to surface
modification and cracks appearing on affected surfaces.
The influence of initial microstructure on tungsten
damaging is clearly demonstrated.
No remarkable damage was observed on the exposed
surfaces under 0.1 MJ/m
2
loads. Nevertheless, the
cracks are found to be propagating in the bulk of
exposed tungsten with longitudinal grain orientation.
Increasing heat load up to 0.2 MJ/m
2
causes the
damaging of all types of tungsten targets. Depending on
W material grade, the observed isolated cracks
propagate to the bulk transversely and parallel to the
exposed surface.
Except for some isolated cracks, no crack networks
are observed on the exposed surfaces under the
abovementioned plasma heat loads.
An effect of the LHD divertor plasma exposure on
the surfaces of the tungsten samples was analyzed. LHD
divertor fluxes are contributed to surface modification
and formation of the sub-surface layer of approximately
82 ISSN 1562-6016. ВАНТ. 2020. №6(130)
10 nm in thickness for all exposed samples. In this
layer, bubbles are found to be formed. Analysis of the
sizes of bubbles suggests that these bubbles might be
attributed to deuterium and helium effects in the LHD
exposures.
For the case of moderate transient loads applied, the
LHD divertor plasma exposures do not reveal any
synergistic effects on the surfaces of the samples, which
pre-damaged by the QSPA Kh-50. Influences of
stronger cracking damage and also melting and
resolidification effects from QSPA pulses on material
performance in the divertor region are planned to be
analyzed in our next step experiments.
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 and 2019-2020 under grant
agreement № 633053. The views and opinions
expressed herein do not necessarily reflect those of the
European Commission.
This work has also been supported by National
Academy Science of Ukraine projects Х-2-11-10/2020
and П-2/24-2020.
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3. Q. Zhou et al. // Fusion Engineering and Design.
2020, v. 159, p. 111879.
4. S. Pestchanyi et al. // Fusion Eng. Design 2011, v. 86,
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Article received 15.11.2020
ПОВРЕЖДЕНИЯ ЧИСТОГО ВОЛЬФРАМА С РАЗНОЙ МИКРОСТРУКТУРОЙ ПРИ
ПОСЛЕДОВАТЕЛЬНЫХ ПЛАЗМЕННЫХ НАГРУЗКАХ В КСПУ И LHD
С.С. Геращенко, О.В. Бырка, В.А. Махлай, M. Wirtz, Н.Н. Аксенов, И.Е. Гаркуша, Ю.В. Петров,
С.В. Малыхин, С.В. Суровицкий, S. Masuzaki, M. Tokitani, С.И. Лебедев, П.Б. Шевчук
Были оценены пороги растрескивания для образцов вольфрама с различной микроструктурой в процессе
повторяющихся плазменных нагрузок КСПУ Х-50. При нагрузках менее 0,1 МДж/м
2
на открытых
поверхностях образцов вольфрама повреждений не наблюдается. Тем не менее трещины наблюдаются в
объеме облученного образца вольфрама с продольной ориентацией зерен. Повышение тепловой нагрузки до
0,2 МДж/м
2
приводит к повреждению всех типов вольфрамовых мишеней. Наблюдаемые трещины
распространяются в объеме в основном поперечно и параллельно облучаемой поверхности.
Проанализировано влияние диверторной плазмы LHD на поверхность образцов вольфрама. Сравниваются
результаты воздействия на образцы вольфрама с различной микроструктурой.
ПОШКОДЖЕННЯ ЧИСТОГО ВОЛЬФРАМУ З РІЗНОЮ МІКРОСТРУКТУРОЮ
ПРИ ПОСЛІДОВНИХ ПЛАЗМОВИХ НАВАНТАЖЕННЯХ У КСПП І LHD
С.С. Геращенко, О.В. Бирка, В.О. Махлай, M. Wirtz, М.М. Аксенов, І.Є. Гаркуша, Ю.В. Петров,
С.В. Малихін, С.В. Суровицький, S. Masuzaki, M. Tokitani, С.І. Лебедев, П.Б. Шевчук
Було оцінено пороги розтріскування для зразків вольфраму з різною мікроструктурою в процесі
повторюваних плазмових навантажень КСПП Х-50. При навантаженнях менше 0,1 МДж/м
2
, на відкритих
поверхнях зразків вольфраму ушкоджень не спостерігається. Проте, тріщини спостерігаються в обсязі
опроміненого зразка вольфраму з поздовжньою орієнтацією зерен. Підвищення теплового навантаження до
0,2 МДж/м
2
призводить до пошкодження всіх типів вольфрамових мішеней. Тріщини поширюються в обсязі
в основному поперечно і паралельно до опромінюваної поверхні. Проаналізовано вплив діверторної плазми
LHD на поверхню зразків вольфраму. Порівнюються результати впливу на зразки вольфраму з різною
мікроструктурою.
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