Radiation resistance investigation of quartz glass KU-1
Results of investigation of the quartz window radiation resistance to fusion reactor conditions are described. The tests of a few selected materials have shown that the best for a visible spectrum region is quartz KU-1 with a large hydroxyl (OH) content. In comparison with other tested types of quar...
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Orlinsk, D.V. Gritsyna, V.T. 2015-05-29T06:16:10Z 2015-05-29T06:16:10Z 2000 Radiation resistance investigation of quartz glass KU-1 / D.V. Orlinski, V.T. Gritsyna // Вопросы атомной науки и техники. — 2000. — № 3. — С. 60-63. — Бібліогр.: 13 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/82370 621.039.66 Results of investigation of the quartz window radiation resistance to fusion reactor conditions are described. The tests of a few selected materials have shown that the best for a visible spectrum region is quartz KU-1 with a large hydroxyl (OH) content. In comparison with other tested types of quartz it has a lowest loss of the transparency, the lowest radioluminescence(RL) intensity and in comparison with other materials (sapphire, cerium glass and spinel) preserved its properties in the widest region of the optical spectrum after neutron, electron and gamma irradiation. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Мagnetic Confinement Radiation resistance investigation of quartz glass KU-1 Article published earlier |
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Radiation resistance investigation of quartz glass KU-1 Orlinsk, D.V. Gritsyna, V.T. Мagnetic Confinement |
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Radiation resistance investigation of quartz glass KU-1 |
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Radiation resistance investigation of quartz glass KU-1 |
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radiation resistance investigation of quartz glass ku-1 |
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Orlinsk, D.V. Gritsyna, V.T. |
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Вопросы атомной науки и техники |
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Results of investigation of the quartz window radiation resistance to fusion reactor conditions are described. The tests of a few selected materials have shown that the best for a visible spectrum region is quartz KU-1 with a large hydroxyl (OH) content. In comparison with other tested types of quartz it has a lowest loss of the transparency, the lowest radioluminescence(RL) intensity and in comparison with other materials (sapphire, cerium glass and spinel) preserved its properties in the widest region of the optical spectrum after neutron, electron and gamma irradiation.
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1562-6016 |
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Radiation resistance investigation of quartz glass KU-1 / D.V. Orlinski, V.T. Gritsyna // Вопросы атомной науки и техники. — 2000. — № 3. — С. 60-63. — Бібліогр.: 13 назв. — англ. |
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2025-11-25T17:46:11Z |
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2025-11-25T17:46:11Z |
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Problems of Atomic Science and Technology. 2000. N 3. Series: Plasma Physics (5). p. 60-63
60
UDC 621.039.66
RADIATION RESISTANCE INVESTIGATION
OF QUARTZ GLASS KU-1
D.V.Orlinski (RRC Kurchatov Institute, Moscow 123182, RF)
V.T.Gritsyna (Kharkiv National University, Kharkiv 61077,Ukraine)
Results of investigation of the quartz window radiation resistance to fusion reactor conditions are described.
The tests of a few selected materials have shown that the best for a visible spectrum region is quartz KU-1 with a
large hydroxyl (OH) content. In comparison with other tested types of quartz it has a lowest loss of the
transparency, the lowest radioluminescence(RL) intensity and in comparison with other materials (sapphire,
cerium glass and spinel) preserved its properties in the widest region of the optical spectrum after neutron,
electron and gamma irradiation.
1. Introduction
Despite of previous numerous investigations [1] a
problem of the transparent material choice for fusion
reactor conditions needs in additional study. Reasons
for this are: (1). The expected neutron fluence for
windows in diagnostic channels may reach of 1018–1019
n/cm2 at ionization dose of 10–100 MGy(Si) (below all
dose units are given for Si) (2). Fusion reactor
radiation conditions (neutron and gamma fluxes and the
ratio between these fluxes) will differ from that of
other sources (3). The choice must be done from
materials of different characteristics.
Therefore the next main problems had to be solved:
(i) The choice of the best material from those which
traditionally are used in thermonuclear devices. (ii) The
study of transparency dependence of the chosen
material (or induced optical density) on fluxes, doses
and type of irradiation. (iii) Radioluminescence (RL)
of material measurement and comparison its intensity
with the plasma visible radiation. (iv). Measurements
the transparency and (RL) in dependence on the
temperature, and search a possibility of thermal
annealing for restoring material characteristics.
Below the results of investigations of some
indicated problems which were accomplished in
European, Japanese and Russian laboratories are
described.
2. The choice of the window material
Materials selected for preliminary tests were three
types of the quartz glass with different content of
hydroxyl – KUVI-S (∼10-4 % OH), KUVI-M (~0.01%
OH) and KU-1 (~0.1% OH); sapphire, aluminum-
magnesium spinel MgAl 2O4 and cerium glass S-96.
Samples of all these materials had diameter of 2 cm
and thickness 0.8 cm.
Several radiation sources were used for tests [2]:
60Co gamma source (dose rate dDγ/dt ≤12 Gy(Si)/s and
dose Dγ ≤1 MGy), pulse electron accelerators LU-40
in Kharkov (pulse duration τ=2.9 µs, repetition
frequency f=12.5-150 Hz, electron energy Ee=10
MeV, average dDγ/dt = 0.15-1.0 kGy/s, Dγ ≤ 8 MGy)
and LU-50 in Sarov (τ=10 ns, f ≤ 2.4 kHz, Ee=50 MeV,
average dDγ/dt ≤ 30 Gy/s, Dγ≤700 kGy); neutron
generator SNEG-13, (neutron flux on samples
dFn/dt ≈ 3x1011 n/cm2s at dDγ/dt ≈ 0.15 Gy/s); nuclear
pool-type reactor (for En > 100 keV,
dFn/dt ≈ 2x1012n/cm2s Dγ ≤ 2.5 MGy). In all cases the
temperature during and after irradiation was not higher
than 30-50oC and the relative transparency was
measured after irradiation at room temperature.
The main results of these tests are as follows: (1).
Transparency of all tested materials is very sensitive to
all kinds of the radiation in a near ultraviolet spectral
region; (2). Spinel and cerium glass totally lost
transparency at the wavelength region λ < 400 nm and
were excluded from further tests, also their
transparencies at λ > 400 nm are almost not sensitive
to irradiation; (3). Sapphire is very sensitive in all
visible region (Fig. 1) and may be used only in an
infrared spectral region [3]; (4). The difference in the
spectral transparency for three types of quartz glasses
is rather weak and all they were left for additional tests.
0
20
40
60
80
100
200 300 400 500 600 700 800
WAVELENGTH, nm
T
R
A
N
S
M
IS
S
IO
N
, %
1.2
1.3
2.2
2.3
1.1
2.1
Fig.1. Optical transmission spectra of sapphire
(curves 1.1 and 2.1), quartz glass KU-1 (1.2 and
2.2) and glass KUVI-S (1.3 and 2.3) before (1.1,
1.2 and 1.3) and after (2.1, 2.2 and 2.3)
irradiation to nuclear reactor neutron fluence of
1018 n/cm2 and γ-dose of 45 MGy [2].
3. Quartz glass optical density measurements
Irradiation of KU-1 samples in the nuclear reactor
up to neutron fluence of 6x1019 n/cm2 (total ionization
dose of ~3 GGy) and with electrons (up to 10 MGy)
have shown that the optical density at λ>350 nm
practically does not changed with exception of a week
absorption band at λ≈620 nm [4]. From the irradiation
61
start the optical density at λ < 350 nm increases
gradually after the dose of ~10 kGy and then, beginning
from ~1MGy, either saturates or even starts to
decrease (Fig.2). Unfortunately time variation was
investigated only under γ-irradiation and only at λ≅215
nm [5,6], so far as all irradiation effects at this
wavelength are most pronounced, and at λ>400 nm are
almost absent [7]. After the irradiation stops the optical
density in the short wavelength region abruptly
decreases and for λ < 350 nm and then shows less
values than measured in situ.
0
0.5
1
1.5
2
2.5
300 310 320 330 340 350 360
Wavelength, nm
∆∆
O
D
, c
m
-1
0,3 GGr
3GGr
Fig. 2. Radiation induced optical) spectra in the
short wavelength region after irradiation to
different total ionization doses [4].
Such results were obtained for the optical
transparency dependence on the neutron flux and
gamma dose rate (Fig.3): the dose rate practically has
no effects in the wavelength region of λ > 400 nm, but
at shorter λ the larger flux leads to the lower
transparency at equal fluences.
0
10
20
30
40
50
60
70
80
90
100
150 200 250 300 350 400
λλ, nm
T
, %
6,4õ10Å11
6,6õ10Å13
Fig.3 Optical spectra in the UV region for two
samples KU-1 with thickness of 2 mm [8]. The
values of the neutron flux under irradiation are
given in frame in units of [n/cm2 c].
Temperature influence on the optical density
during irradiation was studied mainly for λ≅215 nm
[5,6]. At λ ≥ 350 nm its influence is very week [6]. The
higher is the KU-1 sample temperature the faster
increases the optical density during irradiation and the
lower its value is in a saturation region at equal gamma
dose and dose rate. This effect indicates the possibility
to restore the quartz transparency by heating. The direct
check has shown that the transparency of irradiated to
neutron fluence of (1-6)x1019 n/cm2 KU-1 samples
really was restored after gradual heating up to 700-
800oC [8].
4. Radioluminescence of quartz glass KU-1.
It is necessary to be sure that the luminescence of
the chosen window material under neutron and gamma
irradiation will not prevent any optical measurements.
Therefore after the candidate materials where defined,
the study of their luminescence under neutron, electron
and gamma radiation was started. The main difficulties
of such experiments consist in requirement of
measurements in situ and rather low luminescence
intensity. For these measurements the radiation source
should permit the access to the tested samples without
introducing addition radiation sources. This request
excludes the use of stationary nuclear reactors. For low
luminescence intensity measurement it is necessary to
have either very sensitive registration system or high
power radiation source. Actually in experiments were
used 60Co gamma source and neutron generator with
sensitive detection system [9, 10], electron beam from
Van de Graaff accelerator with dose rate of 700 Gy/s
[11] and pulse nuclear reactor with an average dose rate
of 155 kGy/s [12].
To compare luminescence of different materials
the of sapphire, anhydroguide quartz (analog of KUVI-
S) and KU-1 were tested under electron beam [11].
Anhydroguide quartz emission has strongly pronounced
maximum at λ≈450 nm (this maximum was observed
also under X-ray irradiation [5]), which is doubled after
increasing the absorbed dose from 5 to 20 MGy, weak
maximum at λ≈650 nm and maximum in the short
wavelength region. KU-1 glass emission has maximum
around 450 nm and
Fig.4. RL spectra for two types of SiO2 and Union
Carbide UV grade sapphire after 2 h irradiation
with electrons at 15oC, 700 Gy/s, and. ~10-10 dpa/s
[11]
weakly pronounced maximum at 650 nm. Common for
both glasses is increased emission at λ≤300 nm.
Results of absolute measurements of the RL intensity
for tested materials are shown in Fig. 4.
62
Measurements at different temperature T have
shown that KU-1 light emission does not depend on T.
Emission of anhydroguide quartz at ~450 nm decreased
with T and disappears at ~350oC. The spectrum both of
them, corrected for the self-absorption, looks like the
Cherenkov emission (λ-2).
Two identical samples of anhydroguide SiO2 were
irradiated with D-T neutrons and 60Co gammas.
Luminescence results are shown in Fig.5 [9]. The
difference in these spectra consists not only in
emission intensity but also in existence in the lower
spectrum of peak at ~630 nm that is absent in other
spectrum. Data adduced in Table 1 [9,10] allow to
compare luminescence efficiencies for different
materials under irradiation with D-T neutrons and 60Co
gamma quanta. These data show that from the point of
view of minimal RL intensity in a visible spectral
region the best materials are silica glasses and the best
of these - the quartz glass KU-1.
Fig.5. Spectra of photons emitted from high-
purity SiO2 in DT-neutron and 60Co gamma ray
irradiation experiments at room temperature
[9,10]
RL measurements using pulse nuclear reactor have
some advantages as compared with other sources: ratio
of neutron and gamma fluxes is near to expected for the
fusion reactor and pulse character of irradiation allows
to avoid of possible influence of the absorbed dose and
also to measure in one pulse luminescence dependence
on irradiation flux. Luminescence spectrum for this
case is shown in Fig.6. Measurements of the
temperature and preliminary irradiation influence have
shown that temperature increasing from 18 to 100 oC
does not changed luminescence intensity and after
preliminary irradiation up to 6x1018 n/cm2 emission
intensity at λ≈620-670 nm became ~2.5. times larger,
but after further increasing neutron fluence up to
6x1019 n/cm2 intensity decreased by ~20%. Other part
of the spectrum remains unchanged. Results of KU-1
RL measurement at different radiation sources are
given in Table 2.
Comparison of estimated values of plasma
continuum emission and windows RL for expected
ITER conditions has shown [12, 13] that both quartz
types luminescence intensity will not prevent from
plasma diagnostics but sapphire emission intensity is
near the brink of permissible.
5. Discussion
One can see from Fig.1 that mostly radiation induced
absorption is in the UV-region of spectra, and includes
absorption bands at 215 and 260 nm. The 215 nm band
is observed in all silica glasses and is caused by E’
centers, that is formed by trapping a radiolitic hole in
Si-Si bond at the site of oxygen vacancy. The 260-nm
band is more intense for OH- free silica glass (KUVI-
S). It has been attributed to oxygen-related defects,
such as non-bridging oxygen hole centers (NBOHC).
Comparison of influence of reactor’s neutron and
electron irradiation [2,5] on optical absorption leads to
conclusion, that silica glass with high concentration of
OH group (wet glass) is more radiation resistant to
compare with dry glass.
0,0E+00
5,0E-08
1,0E-07
1,5E-07
2,0E-07
2,5E-07
3,0E-07
3000 4000 5000 6000 7000
Wavelength, A
A
ve
ra
ge
r
ad
io
lu
m
in
es
ce
n
ce
i
n
a
p
u
ls
e,
W
/(
cm
A
s
te
r)
Average dose
rate 155 000 Gy/s
Fig.6. RL spectrum of KU-1 glass under irradiation
in the pulse nuclear reactor. Different signs refers to
different measurement cycles [12].
From the spectra of RL under electron excitation
one can distinguish bands in SiO2 at 290, 450 and 650
nm [5]. The nature of indicated bands were discussed in
numerous review papers. Most probable the 650 nm
band is related to NBOHC, the 450 nm is related to the
center of the family of the so-called oxygen-deficiency
centers (ODC’s) - specifically to di-coordinated
silicon -ODC(II). The band at 290 nm also related to
ODC(II) - oxygen di-vacancy. It was found that relative
intensities of bands very sensitive to the source of
irradiation [10,11]. Under electron excitation at dD/dt
= 700 Gy/s the intensity of different bands are
comparable. In DT-neutron experiments dDγ/dt=0.03
Gy/s the intensity of the 450 nm band is the lowest
despite the simultaneous irradiation with neutrons at
the dFn/dt= 4.6x1010 n/cm2s. Under irradiation only in
60Co gamma ray source at higher excitation
dDγ/dt=0.45 Gy/s the intensity of this band increases
by the order of magnitude. Thus, most of this
luminescence comes from the defects (either intrinsic
or newly produced) in electron excitation. From Table
1 one can see that in DT experiments the number
emitted photons per unit of absorbed energy is the
63
lowest for SiO2 to compare with other potentially used
materials for optical windows.
Comparison of the dose rate dependencies of
optical properties of the KU-1 glass irradiated with
pulse electron beam and continuous neutron
bombardment indicates that formation of the stable
optical centers involves the transient processes, that
are dependent on the type of excitation and density of
energy deposition.
The pulsed dose rate at the electron irradiation
comes to instant energy deposition of 2.2 MGy/s [5] in
material that leads to creation the high density of
defects. Post irradiation evolution and interaction
between these transient defects facilitate creation of
the state optical centers. On the other hand, the
continuous irradiation even at the highest neutron dose
rate of 6.6x1013 n/cm2 s produces transient defects
with large spatial separation excluding their mutual
interaction and nonlinear effect of stable center
formation.
6. Conclusion
These investigations were undertaken with the aim
to find and test a suitable material for ITER diagnostic
systems. Obtained data show that in ITER radiation
conditions all types of quartz glass may be used in the
spectral region of 350-2000 nm. Glass KU-1 can stand
at the higher neutron fluence and has a lower RL
intensity than anhydroguide or high purity glass.
At the same time there are some questions which
are left without answers. (i) Expected in a fusion
reactor the irradiation temporal regime can not be
reproduced in test process. (ii) Almost all data on
optical absorption were attained after irradiation.
Optical density in the short wavelength region during
and after irradiation may be different. (iii) The ratio
between neutron and gamma radiation in a fusion
reactor will distinguish from this one used in
experiments. But it is very unlikely that all these
circumstances can change the main result of present
studies – the quartz glass KU-1 is the most suitable
material for diagnostic windows.
References
1. E.J.Friebele. Radiation Effects, in “Optical
Properties of Glass”, Eds D.R.Uhlmann and
N.J.Kreidl (American Chemical Society, 1991)
pp.205-264.
2. D.V.Orlinski, I.V.Altovsky, T.A.Bazilevskaya et al. J.
Nucl. Mater. 212-215 (1994) 1059.
3. A.B.Berlizov, O.V.Kachalov, A.R.Matewosov et al,
“Optical material testing at the nuclear reactor and
at radiating by the steady state gamma rays” in the
ITER Final Report of Russia for the Task Agr. T-28,
1995.
4. DV.Orlinski, K.Yu.Vukolov, Plasma Device and
Operation, 17 (1999) 195
5. V.N.Gritsyna et al., J. Nucl. Mater. 233-237 (1996)
1310.
6. E.R.Hodgson, “Optical windows” in “EU T246
1996-1997 Results”, Garching Technical Meeting,
July 1997
7. V.I.In‘kov et al., J.Nucl. Mater. 256 (1998) 254.
8. K.Yu.Vukolov et al., Problems of Atomic Science
and Technology, Series “Plasma Physics”, Issues 1-
2, Kharkov 1999, p.126.
9. F.Sato, Yu.Oyama, T.Iida et al., Fusion Engin. and
Designs 41 (1998) 207-212.
10. F.Sato, T.Iida, Yu.Oyama et al., J. Nucl. Mater. 258-
263 (1998) 1897-1901.
11. A.Morono and E.Hodgson, ibid. pp.1889-1892.
12. A.Gorshkov, D.Orlinski, V.Sannikov et al., J. Nucl.
Mater. 273 (1999) 145-149.
13. H.Salzmann et al. Design Description Document,
Thomson scattering (core) (WBS 5.5,C.01), 1997,
p.60
Table 1. Number of emitted photons per unit absorbed energy in visible range (350-650 nm)
Sample
Peak wavelength
(nm)
D-T neutrons ++secondary γ-rays
(photons/MeV)
60Co γ-rays
(photons/MeV)
Anhydroguide SiO2 450 17±6 170±60
KU-1 quartz glass 650 14±5 -
Ge doped silica 390 83±30 410±140
Sapphire 410 2500±1000 27000±11000
Table 2. RL in the spectral region of 350-650 nm of KU-1 irradiated from different radiation sources.
Radiation
Source
Operating
condition
Ionizing
dose rate,
(Gy/s)
Displacement
dose rate,
(dpa/s)
Photons number at
350-650 nm
per 1MeV of total
absorbed energy
Ratio of radiated
energy in a region
of 350-650 nm to
absorbed energy
Electron
accelerator
stationary
700
~10-10
80*)
~ 2x10-4
Neutron
generator
stationary
0.5
~10-10
14*)
~ 4x10-5
Neutron
generator
pulse, FWHM
60µs
in one pulse at an
average155,000
~4x10-5
4*)
~ 1x10-5
*) measurement accuracy 30-50 %
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