PR6

Irradiation Effects on Nuclear Advaced Materials Irradiatedby Particles with High Energy
Electron irradiation on W at around 500 ℃ using
KURRI-LINAC(M. Akiyoshi, T. Yoshiie, Q. Xu and K. Sato)
ARS-6
The development of new positron beam system using
KUR(Y. Nagai, K. Inoue, T. Toyama, Y. Shimizu, K. Nagumo,
M. Shimodaira, T. Hirota, K. Sato, T. Yoshiie and Q. Xu)
ARS-7
Radiation damage in bulk amorphous alloys by electron
irradiation(F. Hori, K. Ishii, T. Ishiyama, K. Kobayashi, A. Iwase, Y.
Yokoyama, Q. Xu and K. Sato)
ARS-10
Positron annihilation study of Fe-Cr alloys after neutron
irradiation in KUR(R. Kasada, K. Sato and Q. Xu)
ARS-12
Positron annihilation lifetime measurements austenitic
stainless steels irradiated in the SINQ target irradiation
program(K. Sato, Q. Xu, T. Yoshiie, Y. Dai and K. Kikuchi)
ARS-13
Effects of high energy particle irradiation on hydrogen
retention in refractory metals(K. Tokunaga, M. Matsuyama, S. Abe, H. Osaki, K. Araki, T. Fujiwara, M. Hasegawa, K. Nakamura, Q. Xu and
K. Sato)ARS-14
Dependence of cellular structure formation on ion species(N. Nitta, C. Watanabe, M. Taniwaki, Q. Xu and T.
Yoshiie)Q. Xu
Research Reactor Institute, Kyoto University
OBJECTIVES: Neutron irradiation is usually used toinvestigate radiation effects in solid materials and develop new materials. Unfortunately, because the operation
time of KUR was limit, and the laboratory for neutron-irradiated samples could not be used in 2014, theresearch activities were severely restricted. In the present
report, instead of neutron irradiation, ion, electron and γ
ray irradiations were used to estimate degradation mechanical properties of materials, such as material for optoelectronic and high-power devices.
RESULTS: The allotted research subject (ARS) andthe name of co-researches in each ARS are listed below.
ARS-1
Compensation mechanism of DX-like center in neutrontransmutation doped GaN(K. Kuriyama, T. Nakamura, A. Shikawa, K. Kushida,
and Q. Xu)
ARS-2
Neutron irradiation effects of superconducting magnet
materials at low temperature(T. Nakamoto, M. Yoshida, T. Ogitsu, Y. Makida, K. Sasaki, S. Mihara, K. Yoshimura, H. Nishiguchi, M. Sugano,
M. Iio, Y. Yang, Y. Kuno, M. Aoki, A. Sato, Q. Xu, K.
Sato, Y. Kuriyama and Y. Mori)
Candidate materials, such as Al and Cu alloys, for superconducting magnets of upgraded LHC at CERN andthe muon source for the COMET experiment at J-PARC
were irradiated by LTL at ~10 K. In Al alloys, almost
100% of the defects produced by the irradiation was recovered after warming up to room temperature, however,
several percent of the defects was remained in Cu alloyeven at room temperature.
ARS-3
Study on fine structures formed by high energy particle
irradiation(A. Kinomura, K. Sato, Q. Xu and T. Yoshiie)
ARS-4
Thermoluminescence of Synthesized Calcite(T. Awata, K. Nakashima and Q. Xu)
ARS-5

採択課題番号 26P6

CONCLUSIONS: The defects induced by irradiation
degrade the physical mechanical properties of solid materials. Part of the physical and mechanical properties canbe recovered at high temperatures where defects are mobile. Some experimental results are important for development of large equipment. For example, the results of
ARS-2 indicate that Al alloys can be used in high energy,
high-power accelerator as the material of superconducting magnets since the defects produced by the irradiation
recover when the magnets are warmed up to room temperature.

原子力先進材料における高エネルギー粒子線の照射効果（京大・原子炉）徐 虬

23

プロジェクトPR6-1 Compensation Mechanism of DX-like Center in Neutron Transmutation Doped GaN
K. Kuriyama, T. Nakamura, A. Shinkawa, K. Kushida1,
and Q. Xu2

n = 2(mekBT/2πħ2)3/2exp[(EF-Eg)/kBT],

College of Engineering and Research Center of Ion
Beam Technology, Hosei University
1
Osaka Kyoiku University
2
Research Reactor Institute, Kyoto University

where me is the effective mass of GaN, kB the Boltzmann’s constant. Therefore, the increase of the carrier
concentration with increasing the temperature would be
attributed to the thermal excitation to the conduction bandof electrons trapped in Ni acceptors, as shown in Fig. 1(b).

INTRODUCTION: The 1000 ºϹ annealed neutrontransmutation doped (NTD)-GaN keeps having high resistivity of 108 Ωcm at room temperature. In the present
study, we report the compensation mechanism of DX-likecenter of the neutron transmuted Ge in NTD-GaN.
EXPERIMENTS: GaN epitaxial films on sapphire substrates were irradiated with fast and thermal neutrons atfluences of 6.7 x 1018 cm-2 and 1.4 x 1019 cm-2, respectively. We carried out an alternating current (ac)-Hall
effect measurement and clarified the existence of deepenergy level from the temperature dependence of carrier
concentration in high temperature region.
RESULTS: The resistivity and carrier concentration of
the 1000 ºϹ annealed samples were 2.47 x 106 Ωcm,
4.13 x 1010 cm-3 at 150 ºϹ and 2.37 x 103 Ωcm, 1.60 x1014 cm-3 at 400 ºϹ, respectively. All annealed samples
showed the n-type conduction. The carrier concentration
at both 150 ºϹ and 400 ºϹ were much lower than thecalculated transmuted-Ge concentration (1.24 x 1018cm-3). Fig. 1 (a) and (b) show the schematic diagram of
impurity levels of NTD-GaN. Ge atoms transmuted in
GaN by the two (n,γ) reactions of 69Ga and 71Ga form theDX-like center as donor [1]. Ge is localized at 500 meV
below the bottom of the conduction band from results ofphotoluminescence (PL) measurements [1], supporting
the results of the theoretical calculation [2]. N interstitial(Ni ) atoms generated by NTD-process form the deep
acceptor level at 960 meV below the bottom of the conduction band from present study.14C atoms generated bythe (n,p) reaction are substituted to N sites and forms theacceptor level at 230 meV above the top of the valenceband [3], consistent with the result from the PL measurements[4]. Since the carrier concentration of
NTD-GaN cannot be measured at room temperature,DX-like center of Ge is compensated by both 14C and Ni
acceptors. The Fermi level estimated from the following
equation [5] for a temperature range of 150 - 400 ºϹ was
650 ± 25 meV.

Fig 1. The schematic diagram of impurity levels in
NTD-GaN. (a) the compensation of DX-like center of Ge
donors by 14C and Ni acceptors. (b) the thermal excitationfrom the energy level of N interstitial.
A part of KURRI Progress Report has been publishedin Solid State Communications, 205, 1 (2015).
REFERENCES:[1] K. Kuriyama, T. Tokumasu, Jun Takahashi, H. Kondo,
and M. Okada, Appl. Phys. Lett. 80, 3328 (2002);
Proccedings of 26th Int. Conf. Physics of Semiconductors (Edinburgh, UK) D46 (2002).
[2] P. Boguslawski, J. Bernholc, Phys. Rev. B 56, 9496
(1997).
[3] J. Neugehauer, C. G. Van de Walle, Phys. Rev. B 50,
8067 (1994).
[4] T. Ida, T. Oga, K. Kuriyama, K. Kushida, Q. Xu, andS. Fukutani, AIP Conference Proceedings, 1566, 67(2013) (31st Int. Conf. Physics of Semiconductors,
Zurich, Switzerland, 2012).
[5] G. Burns, in Solid State Physics, (Academic Press, Inc,
1985) Chap.2.

採択課題番号 26P6-1 化合物半導体の照射効果と電気的・光学的物性に関する研究（法政大院）栗山一男、中村 司、新川 輝、（大阪教育大）串田一雅（京大・原子炉）徐 虬
24

プロジェクトPR6-2

Neutron Irradiation Effects of Superconducting Magnet
Materials at Low Temperature

T. Nakamoto, M. Yoshida, T. Ogitsu, Y. Makida, K. Sasaki, S. Mihara, K. Yoshimura, H. Nishiguchi,
M. Sugano, M. Iio, Y. Yang1, Y. Kuno2, M. Aoki2,
A. Sato2, Q. Xu3, K. Sato3, Y. Kuriyama3, and Y. Mori32011 - 2013, CX-1070-SD for 2013 - 2014) showed atemperature drift during neutron exposure due to theirradiation damage. The thermocouple and the Cernox
sensor were placed just behind the samples to measure
the temperature of the helium gas coolant.

J-PARC Center, KEK
1
Department of Applied Quantum Physics & Nuclear
Engineering, Kyushu University
2
Department of Physics, Osaka University
3
Research Reactor Institute, Kyoto University

RESULTS: The fourth irradiation test for the aluminum sample (Al-Y2) and the copper sample was carriedout in April 2014. Another type of aluminum sample with
Ni additive (Al-Ni) was also irradiated at second time.
The irradiation condition is basically same as the previous irradiations. After cooling down to 12 K, the reactor
was turned on to a power of 1 MW. The estimated fastneutron fluence in 53.5 hours operation is 2.7 x 1020 n/m2.
Behavior of the induced resistance by the neutron irradiation is very similar to the previous results. Degradation
rates of the electrical resistivity for both aluminum samples
are
quite
similar:
2.2 x 10-31 "m3
and
-31
3
2.3 x 10 "m for Al-Y2 and Al-Ni, respectively. For
copper sample, the degradation rate is 7.3 x 10-31 "m.
After the irradiation, all samples were warmed up to
room temperature. Anneal effects of the samples were
measured at the subsequent cooling test to 12 K in December 2014 without irradiation. Table 1 lists the summary of irradiation tests so far. For the aluminum samples, the induced resistance was fully recovered to be theoriginal resistance for all cases while the degradation rate
is much higher than copper. This means that the degradedelectrical resistivity of aluminum stabilizer in the superconducting magnet due to the irradiation can be completely recovered by the adequate intervention of warming up to room temperature. For the copper sample,
however, the recovery of the resistance by the thermal
cycle was imperfect for all cases: the recovery rates were
82 % to 96 %. This will concern the safe operation of thesuperconducting magnet at severe radiation environment.

INTRODUCTION: Superconducting magnets will be
subjected to a high neutron fluence of 1021 n/m2 or higher
in the operation lifetime in the high energy particle physics experiments, such as a high luminosity upgrade of the
LHC at CERN and the muon source for the COMET experiment at J-PARC. Since electrical resistivity of a stabilizer at low temperature, which is very sensitive to neutron irradiation, is one of the important parameters for thequench protection of the magnet system. A series of electrical resistivity measurement at neutron irradiation for
the aluminum stabilizer with additives of yttrium takenfrom the prototype superconducting cable as well as
copper stabilizer was started in 2011. In 2014, the fourth
irradiation test with the same samples which were irradiated so far was performed to observe the effect of themultiple irradiations and the thermal cycles to room temperature on the electrical resistivity.
EXPERIMENTS: The irradiation tests have been carried out at a low temperature irradiation facility (LTL) at
E-4 line of KUR. Detailed experimental procedure wasreported in [1]. The aluminum stabilizer samples withdimensions of 1 mm x 1 mm x 70 mm were cut from thesuperconducting cable manufactured by Hitachi Cable.
The copper stabilizer sample has the dimensions of!1mm x 50mm. The electric resistance was measured by
a 4-wire method employing a Keithley 6221 current
source and a Keithley 2182A voltmeter. The temperature
was determined by using a thermocouple of Au(Fe) and
Chromel, since the Cernox sensor (CX-1050-SD for

REFERENCES:[1] M. Yoshida et al., Proc. of ICEC 24-ICMC 2012,685-688, 2013.

Table 1. Summary of irradiation effects on electrical resistivity of stabilizers with multiple neutron irradiations.
Sample, irradiation year
2011
2012
Al-Y2
2013
2014
2013
Al-Ni
2014
2011
2012
Copper
2013
2014

Initial RRR
360
360
368
367
561
566
308
291
285
277

Tirr (K)
12
15
15
14
15
14
12
15
15
14

#tot (>0.1 MeV) (n/m2)
2.6 x 1020
2.6 x 1020
2.6 x 1020
2.7 x 1020
2.6 x 1020
2.7 x 1020
2.6 x 1020
2.6 x 1020
2.6 x 1020
2.7 x 1020$%irr/#tot x10-31 ("m3)
2.8
2.9
2.5
2.2
2.6
2.7
0.93
1.02
0.77
0.73

Recovery Rate (%)
100
100
100
100
100
100
82
92
95
96

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25

PR6-3

Study on Fine Structures Formed by High Energy Particle Irradiation

A. Kinomura*, K. Sato1, Q. Xu1 and T. Yoshiie1

triangle), where the room temperature was assumed to be
27 °C.
Types of major annealed defects are different
depending on the irradiation temperature in the current
temperature range (from room temperature to 400 °C).
Damage peak after thermal annealing at 400 °C was close
to the undamaged level in the RBS/C spectrum, whereas
the damage peak after thermal annealing at 90 °C (in thisstudy) was close to the random level. In spite of thedifference in annealed defects, the Arrhenius plot
provides some insights in terms of the comparison
between neutron-enhanced and ion-beam annealing.
The difference in efficiency between neutron-enhanced
and ion-beam annealing was within one order ofmagnitude, implying that a similar mechanism may be atwork for both of annealing methods.
In summary, the effect of neutron irradiation on
ion-implantation induced damage in Si was investigatedusing the neutron irradiation in KUR. Similar annealing
efficiencies were obtained for neutron-enhanced andion-beam annealing experiments.
ACKNOWLEDGMENT: We would like to thank K.
Yasuda and R. Ishigami of the Wakasa Wan Energy
Research Center and colleagues of AIST for theirassistance on this study.
REFERENCES:[1] A. Kinomura, T. Yoshiie, A. Chayahara, Y. Mokuno,
N. Tsubouchi, Y. Horino, Q. Xu, K. Sato, K. Yasuda, and
R. Ishigami, Nucl. Instrum. Methods Phys. Res. B 334(2014) 48.
[2] A. Kinomura, A. Chayahara, Y. Mokuno, N.
Tsubouchi, Y. Horino, T. Yoshiie, Y. Hayashi, Q. Xu, Y.
Ito, R. Ishigami and K. Yasuda, Appl. Phys. Lett. 88(2006) 241921.

National Institute of Advanced Industrial Science andTechnology (AIST)
1
Research Reactor Institute, Kyoto University*Present address: Research Reactor Institute, Kyoto
University
INTRODUCTION: The effects of ion irradiation havebeen extensively studied for various crystalline materials.
It is known that irradiation causes the damage ofcrystallinity, leading to the degradation of original
material properties.
However, under particular
irradiation conditions, the irradiation effects can induceinteresting phenomena such as ion beam annealing in Si,
where crystallinity of implantation-induced damage
layers are recovered by other ion irradiation. Thus, it isimportant to investigate the irradiation effects ofenergetic particles (ions and neutrons) and the influenceon crystallinity of materials.
EXPERIMENTS:
Neutronenhancedannealing(crystalline recovery) of ion-implantation induced
damage in single-crystalline Si has been investigated tocompare the difference in annealing effects between ion
and neutron irradiations.
Si ion implantation to(100)-oriented Si was performed at 200 keV to a dose of
5×1014 cm-2 to introduce irradiation damage in the sample.
The Si-implanted sample was encapsulated in an Al
capsule with He ambient gas and neutron irradiated for
12 weeks in the core irradiation facility of the Kyoto
University Reactor (KUR) operating at 5 MW. Control
samples were thermally annealed at 90 °C in a quartz
tube furnace with flowing Ar gas for the same annealing
time as the neutron irradiation. The damage levels ofsamples were measured by Rutherford backscatteringwith channeling (RBS/C) using a 2 MeV He ion beam.
RESULTS: Sample temperatures cannot be directly
measured during reactor operation in the case of the KUR
core irradiation facility. In this study, the sample
temperature during the neutron irradiation was estimatedto be below 90 °C by solving a partial differential
equation describing the heat flow inside the sample
capsule made of Al. Since the thermal annealing rate
for heavily damaged Si was nearly constant around 90 °C,
the error of estimated temperature rise does not affect theresult of this irradiation experiment.
The samples before and after irradiation were
measured and damage levels were calculated by taking
account of dechanneling fractions in RBS/C spectra.
Annealing efficiencies obtained in this and previous
studies [1, 2] were plotted (closed circles), under theassumption that the irradiation temperature in this study
was 90 °C. For comparison, efficiencies of ion beamannealing of disorder were also calculated from the databy other groups and plotted in Fig. 4 (closed square andFig. 1 Annealing efficiencies of neutron and ion-beamirradiations.
Closed circles (neutron), triangle andsquare (ion) correspond to the original efficiencies.
Open circles (neutron), triangle and squares (ion)correspond to the efficiencies corrected based on
displacement-rate dependence.

採択課題番号 26P6-3 高エネルギー粒子照射に関わる材料の微細構造の研究（産総研）木野村淳 （京大・原子炉）佐藤紘一、徐
、義家敏正
26

プロジェクトPR6-4

Thermoluminescence of Synthesized Calcite

T. Awata, K. Iwasaki, S. Tanaka, Q. Xu1

X-, Y- and Z- axes indicate emission wavelength (nm) of
emission, temperature and intensity, respectively. Thereis one peak at 620nm starting from 285K same result as

Department of Physics, Naruto University of Education
1
Research Reactor Institute, Kyoto University
INTRODUCTION: We reported that thermoluminescence (TL) of natural calcite (CaCO3) irradiated by
gamma rays [1-2]. In that result, it was shown that thealmost spectra of TL had only one orange emission peakat 620nm, and that may be originated from a small
amount of impurity of Mn2+ in Calcite [3]. In this study,
we have artificially synthesized calcite with different
kinds of impurity using chemical reaction in water solution, and compared TL spectra of these with natural calcite, and to clear the relationship with emission and kindsof impurity.

Fig. 2 TL 3D spectrum of synthesized calcite with Mn
irradiated by gamma rays.
former our experiment of natural calcite [2]. It is clearthat 620nm emission peak at calcite is originating fromexistence of small amount of Mn. This result is supported
by study of Medlin [3]. Figure 3 shows those TL spectraof synthesized calcite with Mn, Mn+Ce and Mn+Pb at
maximum intensity temperature. Mn and Mn+Pb spectra
looks alike, and have one peak at 620nm same as former
our experiment. As Mn+Ce spectra, it has one peak at
640nm which is different from other two samples. Comparing this result with photoluminescence one makes it
possible to be clear that reason.

EXPERIMENTS: Calcites were synthesized by achemical reaction method in water solution [4]. 1.5% of(NH4)2CO3･H2O(1.5g in 100mL pure water) and 1.8% of
CaCl2･6H2O (2g in 100mL pure water) with 0.01g element impurity were mixed at room temperature. After
mixed, these solutions were precipitated by holding for
two weeks, and filtering. After filtering, samples wereshaped by a tablet machine. We have made three samples
with different element impurities (Mn, Mn+Ce, Mn+Pb).
These samples were irradiated 60Co gamma rays for 1h(about 20kGy) at 77K using KUR gamma-ray facility.
The thermoluminescence spectra were measured by aphoto-spectrometer (Princeton Instrument Spectra Pro
300i) with a temperature controlled system (77K to413K).

4[ 10 ] 5

Intensity (arb.)

4

RESULTS and DISCUSSION: Fi gur e 1 s ho ws t hethermoluminescence picture of synthesized calcite with
an impurity Mn and Mn+Ce by gamma rays irradiation.
This picture was taken by stereo microscope after pick-

Mn
Mn+Ce
Mn+Pb

3
2
1
0

400

500

600
700
wave length (nm)800

Fig.3 TL spectra of synthesized calcite with Mn,
Mn+Ce and Mn+Pb.
REFERENCES:[1] T. Awata, T. Kishino, F. Maki and Q. Xu, KURRI
Progress Report 2011, p.143.
[2] T. Awata, K. Nakashima and Q. Xu, KURRI Progress
Report 2013 p.169.
[3] W. L. Medlin, J. Opt. Soc. Am. 53(1963)1276.
[4] G. R. Fonda, J. Phys. Chem. 44(1940)435.

Fig. 1 Thermoluminescence of synthesized calcite with
an impurity of Mn (left) and Mn+Ce (right).
ing out from liquid nitrogen. Both pictures show orange
emission almost same as natural calcite with Mn element[2]. Figure 2 shows a 3D thermoluminescence spectrumof calcite with Mn impurity irradiated by rays at 77K
from 93K to 413K with heating speed at 0.32K/second.

採択課題番号 26P6-4
イオン性結晶材料の放射線誘起発光機構（鳴門教育大学）粟田高明、岩崎健太郎、 田中聡（京大・原子炉）徐虬
27

プロジェクトPR6-5

Electron irradiation on W around 500℃ using KURRI-LINAC

M. Akiyoshi1, T. Yoshiie2, Q. Xu2, K. Sato2

nuclear reaction will activate Ag atoms very strongly, so
it cannot be used. In addition, conventional (horizontal)
graphite sheet (Panasonic PGS graphite sheet,
EYGS-182310 t=0.10mm, TC=700W/m・K) is used tospread heat horizontally.
The piled graphite sheets and specimen holders aretighten with screws and nuts made by Ti to avoid radio
activation. This pile is put between Al square tubes withthe vertical-graphite seats. All specimens and Cu plates
are coated by BN spray to avoid surficial oxidation. In
addition, a Cu aperture was put in front of the specimen
pile to trim down the beam irradiated on out side of thespecimen that heats the pile wastefully.
Pure W specimens (Nilaco) was cut into φ10 and thethickness was 0.5mm (2 pieces) and 1.0mm (1 peace). α-Al2O3, β-SiC specimens （φ10×0.5mm）are also
irradiated.

1

Faculty of Engineering, Kyoto University(from 2015.04: Radiation Research Center, Osaka Prefecture University )2
Research Reactor Institute, Kyoto University
INTRODUCTION:
It is well known that irradiation induced damages inceramics showed significant degradation in thermal diffusivity unlike metals. In addition, the dependence ofthermal diffusivity on measurement temperature is affected with irradiation induced damages. Therefore,
thermal diffusivity during the irradiation is still not estimated. To resolve this problem, kinetic analysis is required where most important information is the behaviorof point defects. Electron irradiation is the best choice toinduce simple Frenkel pairs.
In these days, W (tungsten) material is considered as a
candidate for divertor material in future fusion reactor. W
is metal, of cause, but showed a similar behavior ofthermal diffusivity. It shows relatively small thermal diffusivity arisen from low electron conductivity, but shows
dependence on measurement temperature like ceramics
caused by phonon-phonon scattering.
In this study, we irradiated W specimen using KURRI-LINAC and check the specimen temperature during
the irradiation, and also radio-activity of specimens.

RESULTS:The beam condition was Acc. Energy: 32MeV, Pulse
length 4s, Peak current: 550mA. The frequency wasonce increased to 110Hz, but specimens showed a trendof over heating, so the frequency was settled down to100Hz. Even at that frequency, the total beam energy was
7.0kW in several cm2 that can compare with the heat flux
on divertor in the fusion reactor ITER which is planed as
10MW/m2. This irradiation system got over this high heat
flux and achieved reliable irradiation at around 550℃.
The irradiation damage induced by the electron irradiation is calculated. For the most ceramics, 2.82×1020
electrons in 2cm2 accelerated to 32MeV induces defects
up to 1.00 × 10-2dpa (target mass M=16amu, atomic
number Z=8, knock on energy Ed=30eV). W is far heavier (M=183.8amu) and knock on energy is larger(Ed=100eV), but the collision cross section is 48.4barn
while ceramics shows only 18.7barn. It is said that the Edof W is a little smaller, and if it is 80eV, the cross section
is 60.1barn. Therefore, induced damage in W is larger
than typical ceramics, 1.48×10-2dpa (Ed: 100eV) ～1.95
×10-2dpa(Ed: 80eV).
After the irradiation, radio-activity of the specimen
holder and specimens was investigated. The whole irradiation holder showed over 100mSv/h in the surface at 17h
after the beam stop, 55mSv/h at 33h and 38mSv/h at 40hthat corresponds t1/2 = 13.7h. The half-time of W-185 is
75.1day and W-187 is 23.7h while Cu-64 is 12.7h, so themost of the activity was assumed to be arisen from
Cu-64.

EXPERIMENTS:
In the previous work, 30MeV electron accelerator
KURRI-Linac is used to induce point-defects in bulk
specimens of typical structural ceramics to 1.5x1024e/m2
which correspond to 0.01dpa in typical ceramics. The
irradiation was performed in a new irradiation systemconstructed to achieve an irradiation at around 400℃
where interstitial atoms have enough mobility to migrate.
In the previous work, ceramic specimens were irradiatedusing this irradiation system. In the system, a specimen issettled in a Cu specimen-holder, and holders are piled
between Cu heat spread plates and graphite heat spreadseats. Usually, a graphite seat spreads heat well horizontally, but the graphite seat in this system is `Vertical-Graphite' (produced by Hitachi Chemical) of which
thermal conductivity vertical to the seat is 90W/m・K.
This vertical-graphite sheet was 0.15mm in thickness andwas cut into φ10 that cover the specimen to have goodthermal contact on the surface. In conventional system,
heat contact is achieved by thermal grease that contains
Ag powders. But in this system, neutrons from photo-

採択課題番号 26P6-5
電子線照射後セラミックス中の欠陥評価
プロジェクト（京大・工）秋吉 優史、高木 郁二（京大・原子炉）義家 敏正、徐 虫L、佐藤 紘一
28

PR6-6

The Development of New Positron Beam System Using KUR

Y. Nagai, K. Inoue, T. Toyama, Y. Shimizu, K. Nagumo,
M. Shimodaira, T. Hirota, K Sato1, T. Yoshiie1, Q. Xu1

blocks. After passing the bends, the slow positrons aretransported to sample chamber at an energy up to 20 keV.

Institute for Materials Research, Tohoku University,
1
Research Reactor Institute, Kyoto University

INTRODUCTION: Positron annihilation spectroscopy
is well-known to be a powerful to detect vacancy-type
defects. In 2000 years, it is found that the positron is also
sensitive to (sub)nano embedded particles (SNEPs) withhigher positron affinities than that of the host, even if the
SNEPs are free from open-volume defects. The representative case is ultrafine Cu precipitates in Fe.
We are developing a new positron annihilation apparatus, positron age-momentum correlation (AMOC), tostudy the correlation between the Cu precipitates and thevacancy-type defect induced by neutron irradiation in thelight water reactor pressure vessel (RPV) steels, which isimportant to understand the irradiation induced
embrittlement of the RPV steels due to long-term
in-service exposure to neutron irradiation. For this study,
an intense positron source is required to achieve higher
count rates because typically it takes more than one week
for one spectrum by the conventional AMOC system using 22Na positron source.
In this work, a new positron beam facility with highpositron intensity is constructed at the Kyoto University
Research Reactor (KUR), which is the first reactor based
positron beam in Japan[1].
EXPERIMENTS and RESULTS: An in-pile positronsource was installed at the B-1 hole (20 cm in diameter)
in KUR. The positron beam line consists of two parts:
one is located inside the reactor, and the other is locatedoutside the reactor as shown in Fig. 1 [1,2]. Positrons are
generated by pair production from high-energy γ-rays.
The γ-ray flux and the thermal neutron flux at the positron source position are about 1.5×1012 n/cm2 and 105
Gy/h, respectively, at 5 MW. A W converter of 1 mm
thick and 3 cm diameter and W moderators with a Cd
shroud are used to obtain slow positrons as shown in Fig.
2. In order to enhance the positron generation, a 1 mm
thick Cd shroud covered with an Al plate was mounted
on the top of the magnetic field to cap the converter andmoderator, because high energy γ-ray are generated by
the 113Cd(n, γ)114Cd reaction. The moderators were annealed after the W strips were set in lattices. When annealing, they were encased in covered boxes of 50
μm-thick W foil and the boxes were irradiated on the
covering lids with electron beam welder at KEK in Tsukuba [3]. The annealing temperature was elevated to approximately 2400℃. The vacuum of the welder chamber
was about 10-5 torr. The slow positrons emitted from themoderator were subsequently accelerated up to 30 eV andconfined magnetic fields of several mT. In order to eliminate the background of fast neutrons and γ-rays from thereactor core, the slow positron beam passes two bends inshields consisting of polyethylene, concrete and lead

Figure 1: A schematic diagram of KUR positron
beam system [1,2].

Figure 2: A schematic diagram of the in-pile positron source at KUR [1,2].
Figure 3 shows the positron beam spot recorded using
a microchannel plate (MCP). The beam has a slightly
elliptical shape and the major and minor axes have length
about 2.0 and 1.5cm, respectively. The lattice structure of
W moderator is clearly visible. The positron beam intensity is determined about 106 e+/s at 1 MW by Ge detector.

Figure 3: The observation of positron beam from
KUR using microchannel plate.
REFERENCES:[1] Q Xu et al, J. Phys. Conf. Ser. 505 (2014) 012030.
[2] K Sato et al, Nucl. Inst. Meth. Phys. Resear. B 342(2015) 104.
[3] K Wada et al, Eur. Phys. J. D 66 (2012) 37.

採択課題番号 26P6-6
KUR を用いた新しい陽電子源の開発と材料研究への応用
プロジェクト（東北大・金研）永井康介、井上耕治、外山健、清水康雄、南雲一章、下平昌樹、廣田太一（京大・原子炉）義家敏正、徐虬、佐藤紘一
29

PR6-7

Radiation Damage in Bulk Amorphous Alloys by Electron Irradiation

F.Hori, K.Ishii, T.Ishiyama, K.Kobayashi, A.Iwase,
Y.Yokoyama1, Q.Xu2 and K.Sato2

RESULTS: The mean positron lifetime τ of all
as-quenched sample was about 165 2 psec. Before
irradiation, no difference of positron lifetime for different
amorphous alloy systems was observed. This shows that
open volume existing in amorphous is apparently same.
However, the CDB spectra of these alloys before
irradiation are not necessarily same. Take into account forthese facts, it can be deduced that total electron density ofopen volume in any amorphous alloy is almost same but
the real size of open space and chemical ratio around it
depending on alloy composition is not same for various

Dept. of Mater. Sci., Osaka Prefecture University
2
Institute of Materials Research, Tohoku University
1
Research Reactor Institute, Kyoto University
INTRODUCTION: Bulk amorphous alloys are
expected to be useful for various applications because
they have superior mechanical properties such as
strength, hardness and corrosion resistance. We havebeen suggested that the properties of bulk glassy alloys
can be improved by high energetic particles irradiation.
So far, we have reported that effects of free volume
and mechanical properties on the bulk amorphousalloys depend upon the irradiation species [1,2]. Alsochange in free volume by the irradiation strongly reflects
various properties such as hardness and ductility of bulk

compositional alloys. Figure 1 shows the change inpositron annihilation lifetime by electron irradiation as
a function of Zr composition ratio in bulk amorphousalloys. It found that the increasing trend of positron

lifetime becomes smaller with increasing of Zr
contents. Especially, we found that radiationinduced open volume change is suppressed in glassy
alloys including more than 60% Zr atoms.

amorphous alloys. Recent years, eutectic ZrCuAl bulk
glassy alloy shows the degradation of ductility andtoughness by annealing but that for hypoeutectic
remains unchanged after annealing. In order toestimate irradiation effects for various compositionalbulk amorphous alloys, we performed electron
irradiation for various kinds of ZrCuAl bulk amorphousalloys. Before and after irradiation, we have examined
X-ray diffraction, differential scanning calorimetry (DSC)
and positron annihilation.
EXPERIMENTS: ZrxCu90-xAl10 (x=50, 55, 60, 65)bulk amorphous alloys with 8 mm in diameter and 60 mm
in length were prepared by a tilt casting technique. For
positron annihilation measurements, alloy samples were
cut into the size of about 0.5 mm thickness disk. 8 MeV
electron irradiations with total dose of 2x1018 e/cm2 was
performed for these alloys at 320 K by LINAC at
Research Reactor Institute, Kyoto University. During
irradiation, samples were cooled in water flow path.
Irradiated samples were examined by X-ray diffraction,
positron annihilation lifetime and coincidence Doppler
broadening measurements at room temperature. The
positron annihilation lifetime spectra consist of more than
1.0 x 106 counts. The positron lifetime spectra wereanalyzed by using POSITRONFIT program.

Fig. 1 Change of positron lifetime for various compositions of
ZrCuAl bulk amorphous alloys by 8 MeV electron irradiation.
REFERENCES[1] N.Onodera, A.Ishii, Y.Fukumoto, A.Iwase, Y.Yokoyama,
and F.Hori, Nucl. Inst. & Meth. B. 282 (2012) 1[2] F.Hori, N.Onodera, A.Ishii, Y.Fukumoto, A.Iwase,
A.Kawasuso, A.Yabuuchi, M.Maekawa and Y.Yokoyama, J.
Phys.: Conf. 262 (2011) 012025

	
 採択課題番号 26P6-7	
 金属合金における照射効果の研究
	
  	
  	
  	
 
	
 
プロジェクト
（阪府大・工）堀史説、石井康嗣、石山大志、小林一基、岩瀬彰宏、（東北大・金研）横山嘉彦	
 	
 (京大・原子炉)徐虫 L	
 、佐藤紘一	 30

PR6-8

Positron Annihilation Study of Fe-Cr Alloys after Neutron Irradiation in KUR

R. Kasada1, K. Sato2, Q. Xu31018 n/cm2). Positron annihilation lifetime spectrometry
was carried out for investigating open-volume type defects produced by irradiation.

1

Institute of Advanced Energy, Kyoto University
Department of Mechanical Engineering, Kagoshima
University
3
Research Reactor Institute, Kyoto University

2

Results and Discussions: Results of positron annihilation lifetime spectrometry is shown in Table 1. There isno meaningful difference in the mean lifetime of unirradiated Fe-Cr binary alloys. After the neutron irradiation
in KUR, the mean lifetime of pure Fe and Fe-xCr alloys
for x ≤ 85 slightly increased but not decomposed into
multi-components. On the other hand, that of Fe-91Cr
and pure Cr showed two- and three components, respectively. This results indicate that Fe atom suppress vacancy cluster formation in the Fe-Cr binary alloys from aview of the Cr-rich side. Further investigation is needed
for understanding the effect of Cr (or Fe) atom on theformation of vacancy type cluster in Fe-Cr alloys.

INTRODUCTION: Ferritic steels containing Cr are
expected to be used for the first-wall component of thefusion reactors as well as for the fuel pin cladding of theGeneration IV nuclear fission systems [1]. However,high-Cr steels may suffer from thermal aging embrittlement, which is well-known 475 °C embrittlement. This ismainly due to hardening phenomenon through the phaseseparation of Fe and Cr as shown in the phase diagram.
In the previous study [2], we applied a positron annihilation spectrometry to detect the phase separation in the
Fe-Cr alloys after thermal aging at 475 °C.
The present collaborative research has investigate theneutron irradiation effect on the positron annihilation
lifetime of Fe-Cr alloys.

REFERENCES:[1] A. Kimura, et al., Journal of Nuclear Science andTechnology, 44 (2007) 323-328.
[2] R. Kasada and K. Sato, submitted to J. Alloys andCompounds.

Experimental Procedure: Materials used in the present
study are Fe-xCr binary alloys. Neutron irradiation onthese materials was carried out at 300 °C up to 199 h in
KUR. The displacement damage is 2.1 × 10-3 dpa (5.1 ×

Table 1 Results of positron annihilation lifetime spectrometry of Fe-Cr
alloys before and after neutron irradiation in KUR.
Materials
Fe
Fe-9Cr
Fe-15Cr
Fe-30Cr
Fe-45Cr
Fe-50Cr
Fe-70CrFe-85Cr
Fe-91Cr
Cr

Unirr.
τm (ps)104 ± 1
107 ± 1105 ± 1105 ± 1105 ± 1105 ± 1105 ± 1104 ± 1105 ± 1103 ± 1Irr.
τ1 (ps)109 ± 1109 ± 1109 ± 1109 ± 1109 ± 1108 ± 1
107 ± 1110 ± 1113 ± 124 ± 4I1 (%)

τ2 (ps)I2 (%)

τ3 (ps)I3 (%)

93 ± 19±1383 ± 9156 ± 27±1
48 ± 1502 ± 343 ± 1

採択課題番号26P6-10
鉄クロム系合金の相平衡に及ぼす照射影響
プロジェクト（京大・エネ理工研）笠田竜太（鹿児島大・理工）佐藤紘一（京大・原子炉）徐虬

31

PR6-9Positron Annihilation Lifetime Measurements of Austenitic Stainless Steels
Irradiated in the SINQ Target Irradiation Program

K. Sato, Q. Xu1, T. Yoshiie1, Y. Dai2 and K. Kikuchi3

100 K from 423 to 1323 K. After annealing, samples
were cooled down by air cooling. Cool time to room
temperature was about 20 minutes.

Graduate School of Science and Engineering, Kagoshima
University
1
Research Reactor Institute, Kyoto University
2
Spallation Neutron Source Division, Paul Scherrer Institut
3
Frontier Research Center for Applied Atomic Sciences,
Ibaraki University

RESULTS: Short and long lifetime component in thetwo component analysis was 150 (6) ps and 237 (7) ps,
respectively. Intensity of short and long lifetime component was 49 (7) % and 51 (7) %, respectively. Errors areshown in parentheses. The long lifetimes result from theformation of vacancy-cluster–He-atom (Vm-Hen) complexes (large open space defects), while the short lifetimes denote the formation of stacking fault tetrahedra(SFTs), dislocation loop, and single-vacancy–He-atom(V-Hen) complexes (small open space defects). The experimental value of 230 ps is slightly smaller than thecalculated positron lifetime of 249 ps for 4-vacancy clusters (V4) in Ni. Yet the vacancy cluster size is not likely
to be less than 4, because many He atoms formed in thesamples during irradiation. The positron lifetime of the
He bubbles decreases as the number of He atoms in avacancy cluster increases. Thus the exact vacancy cluster
size cannot be determined, because they are too small tobe directly observed by TEM.
The positron lifetime does not change after isochronal annealing up to 623 K. The spectra only show one
component for annealing between 723 and 923 K, butthey resolve into two components when annealed above
1023 K. It is expected that Vm-Hen complexes absorb He
atoms by annealing at temperatures up to 623 K. Because
the complexes incorporate many He atoms after irradiation, the lifetime decrease caused by absorption of helium
may become saturated. In this stage, the He bubble concentration does not change because the long lifetime intensity is almost constant. SFTs and V-Hen complexes are
expected to dissociate after annealing at 623 K. These
defects, which have a short lifetime for annealing at up to523 K, tend to aggregate and Vm-Hen complexes areformed. It is impossible to resolve them into two components. A small increase in the mean lifetime arises because of both the growth of Vm-Hen complexes and theirrelease of H atoms. The Vm-Hen complexes dissociate
after annealing at 1023 K. In this stage, the absorption ofvacancies is larger than that of He atoms, and therefore,
the long lifetime increases.

INTRODUCTION: Austenitic stainless steels havebeen known as highly corrosion resistant materials andimportant nuclear materials. There have been a number ofstudies on the void swelling behavior of them [1,2]. Recent theoretical and experimental analyses have revealed
the importance of incubation period, a transient stage
before the steady growth of voids. However, experimental results of void swelling in austenitic stainlesssteels have been limited to high dose. Because most ofexperimental studies have been performed by transmission electron microscopy after observable void formation,and point defects and their clusters under the resolution
limits are impossible to detect. Therefore, point defectprocesses during the incubation period are not clear. In
this study, the effect of alloying elements on defectstructures in austenitic stainless steels and their model
metals during the incubation period was studied after
neutron irradiation by using positron annihilation lifetime
measurement.
EXPERIMENTS: Titanium-doped 316-type austenitic
stainless steel, called Japanese Primary Candidate Alloy(JPCA), and the reduced activated ferritic/martensitic
steel F82H were used in this study. The JPCA was irradiated in the first SINQ (Swiss Spallation Neutron Source)
target irradiation program (STIP-I). More details of the
STIP-I experiments have been previously reported [3].
Irradiation position was F21. Irradiation temperature was
413K, and irradiation dose was 6.3dpa. After implementing a fatigue test on JPCA at room temperature, the positron annihilation lifetimes of the undeformed area of thesample were measured at the Research Reactor Institute,
Kyoto University. A three-detector system using a fast
digital oscilloscope and BaF2 scintillators [4] was adopted for the positron annihilation lifetime measurements,
thereby reducing the background counts and making it
possible to measure highly radioactive samples. The time
resolution of the system was 150 ps (full width at half
maximum). Each spectrum was accumulated to a total of
1.5 × 106 counts. The resulting spectra were analyzed
using the PALSfit program [5]. The isochronal annealingof the positron annihilation lifetime was examined every

REFERENCES:[1] F.A. Garner, Materials Science and Technology, Vol.
10 (VCH Weinheim, 1994), p. 419.
[2] T. Okita et al., J. Nucl. Mater. 307−311 (2002) 322.
[3] Y. Dai and G.S. Bauer, J. Nucl. Mater. 296 (2001) 43.
[4] H. Saito et al., Nucl. Instr. Meth. Phys. Res. A 487(2002) 612.
[5] J.V. Olsen et al., Phys. Stat. Sol. C 4 (2007) 4004.

採択課題番号 26P6-12 電子照射と中性子照射によって形成した金属中の格子欠陥と プロジェクト
ガス原子の相互作用の解明（鹿児島大院・理工）佐藤紘一（京大・原子炉）徐虬、義家敏正（九大・応力研）大澤一人（産総研）大島永康
32

PR6-10 Effects of High Energy Particle Irradiation on Hydrogen Retention in Refractory Metals
K. Tokunaga, M. Matsuyama1, S. Abe1, H. Osaki2, K.
Araki, T. Fujiwara, M. Hasegawa, K. Nakamura, Q. Xu3
and K. Sato3

gas was about 5 %. Temperatures of pre-heating and T
exposures were 100 oC. After the exposure to T gas, T
amount retained in surface layers of the sample was
evaluated by -ray-induced X-ray spectrometry (BIXS)
and imaging plate (IP) measurements.

Research Institute for Applied Mechanics, Kyushu University
1
Hydrogen Isotope Research Center, University of Toyama
2Interdisciplinary Graduate School of Engineering Sciences, Kyushu University
3
Research Reactor Institute, Kyoto University

RESULTS: Temperature of the W samples during theelectron irradiation was 85 oC. Figure 1 shows the resultof the IP measurement of ITER grade W(1) (IG W(1))
and ITER grade W(3)(IG W(3)). The IP images indicatethat amount of T on the surface of IG W(3) is larger thanthat of the surface of IG W(1). Comparison with thestandard samples shows that amount of T of the surfaceof IG W(1) and IG W(2) are 0.0604 kBq/mm2 and 0.166
kBq/mm2, respectively. Figure 2 show line analyses of
PLS value of the surface of IG W(3) (a) and IG W(1) (b)after the T exposure. It can be seen that line profiles arealmost constant. These result indicates that T is easy todiffuse parallel direction for rolling direction. Electron
beam irradiation effect will be discussed by comparing
with the result of un-irradiated W samples.

INTRODUCTION: It is of importance to clarify phenomena of implantation, retention, diffusion and permeation of tritium on surface of the armor materials of thefirst wall/blanket and the divertor on fusion device from aviewpoint of precise control of fuel particles, reduction oftritium inventory and safe waste management of materials contaminated with tritium (T). Refractory metals suchas tungsten (W) is potential candidate for an armor of thefirst wall and the divertor plate of the fusion reactor because of its low erosion yield and good thermal properties.
The armor material will be subjected to heavy thermalloads in the steady state or transient mode combined withhigh energy neutron irradiation that will cause serious
material degradation. In addition, high energy runaway
electrons would bombard the armor materials along theequatorial plane in fusion device. It is considered thatthese cause radiation damage and enhance tritium retention. In the present works, T exposure experiments havebeen carried out on W samples which were irradiated byhigh energy electrons using LINAC in KURRI of Research Reactor Institute, Kyoto University to investigate
effects of high energy electrons irradiation and microstructure on tritium retention of W.

Fig. 1. Tritium image of ITER grade W(3) (IGW(3) and ITER grade W(1)(IG W(1). Bottom parts
are standard samples.

PLS/hr

PLS/hr

EXPERIMENTS: W samples used in the present experiments were two oriented ITER grade W. One was W
sample (ITER grade W(1)) which the surface were manufactured to be oriented parallel to the rolling surface androlling direction. The other was W sample (ITER grade
W(3)) which the surface were manufactured to be oriented perpendicular to the rolling surface and rolling direction. The sizes of W samples were 10mm x 10mm x
1mm. The surface of the both samples were polished tobe mirrored． High energy electrons irradiation has been
carried out using LINAC in KURRI of Research Reactor
Institute, Kyoto University. An energy of electron irradiated was 10 MeV and DPA was 3.26 x 10-3. Temperatureduring the irradiation was measured by thermocouples
which was contacted with a backside of the W samples.
After the electron beam irradiation, T exposure experiments have been carried out using a T exposure device in
University of Toyama. Pressure of the T gas was 1.3 kPa
and T exposure was kept for 4 h. T concentration in the

0.014
0.012
0.010
0.008
0.006
0.004
0.002
0.000

0.014
0.012
0.010
0.008
0.006
0.004
0.002
0.000

IG W(3)

(a)

0

2

4
6
8
Position (mm)12IG W(1)

(b)

0

10

2

4
6
8
Position (mm)1012Fig. 2. Line analyses of IG W(3) (a) and IG W(1) (b)after tritium exposure.

採択課題番号 26P6-13

高融点金属における水素吸蔵特性に及ぼす
プロジェクト高エネルギー粒子線照射効果（九大・応用研）徳永和俊、荒木邦明（九大・総理工）尾崎浩詔（京大・原子炉） 徐 虬、佐藤紘一

33

PR6-11

Depenedence of Cellular Structure Formation on Ion Species

N. Nitta1, C. Watanabe1, M. Taniwaki1, Q. Xu2, T.
Yshiie2
1School of Environmental Science and Engineering,
Kochi University of Technology
2
Research Reactor Institute, Kyoto University
INTRODUCTION: Fine cellular structure is formed on
GaSb, InSb and Ge semiconductors by ion irradiation asshown by Fig. 1[1]-[6]. The authors proposed an idea that
this structure is formed by the behavior of point defects
induced by ion irradiation, that is, first the voids form
from the oversaturated vacancies and they develop byabsorbing point defects induced continuously during ion
irradiation. This idea has been proved by intense studies
on the ion dose dependence and temperature dependenceof the cellular structure. However, the authors do nothave detailed understanding over all the cell formation
process. Especially, the details of the formation mechanism of voids are not yet clear. Though the authors havesurely observed the voids prior to the development of thecellular structure, the diameter of these voids are so large(30-50 nm) and the smaller voids are not yet found, thenlarge voids appear suddenly during ion irradiation, notdeveloping from small voids. Therefore another effect on
voids formation, for example, the thermal spike, is suspected. Thermal spike effect depends on the mass of ions,then, the authors aim to investigate the ion mass dependence of the voids formation and development in this work.
In addition, the chemical effect of implanted ions is studied.

100nm
Fig. 1. FE-SEM image of GaSb surface by 60
keV Sn+ implanted GaSb to a dose of 1.2  1015
ions/cm2 at 150 K.
irradiated sample have small diameters less than 30 nm,
but some of the voids (the density is about 2/1 m2) haveabout 100 nm diameter. These relatively large voids are
removed their top surfaces but seem to consist of single
void.
In Si irradiated wafer, some small contrasts which mightshow the voids were observed, and their density was
about 2/1m2. However, in Al ion irradiated samples, thevoid contrast was not observed. These atom masses are sosmall (26.98 and 28.09) that the ion range is large anddistribution is wide, therefore it is considered that the
point defects density is too small for voids formation anddevelopment.
By SEM study which has been performed until now, it
was assured that the atomic mass of irradiated ion affects
the voids formation and development. However, from
SEM study we cannot know much under the surface, then,the details are not yet clarified. The authors will study
under the surface by cross-sectional TEM in order to understand the void formation mechanism.

EXPERIMENTS: The GaSb (001) wafers were implanted by C, Si, Ge, Pb (IV elements as Sn), Al and P
ions by accelerated by 60 kV voltage to the dose of 10 15
ions/cm2. The wafers were kept at 100-110 K during ion
irradiation. The surface morphology of the implanted
wafers was observed by a FE-SEM.

REFERENCES:[1] 新田紀子, 谷脇雅文, 鈴木朝夫, 林 禎彦, 佐藤
裕 樹 , 義 家 敏 正 , 日 本 金 属 学 会 誌 , 64 (2000),
1141-1147.
[2] N. Nitta, M. Taniwaki, T. Suzuki, Y. Hayashi, Y. Satohand T. Yoshiie, Materials Transactions, 43 (2002),
674-680.
[3] N. Nitta, M. Taniwaki, Y. Hayashi and T. Yoshiie, J.
Appl. Phys., 92 (2002), 1799-1802.
[4] N. Nitta, M. Taniwaki, Y. Hayashi and T. Yoshiie,
Physica B, 376-377 (2006), 881-885.
[6] N. Nitta, T. Hasegawa, H. Yasuda, Y. Hayashi, T. Yoshiie, and M. Taniwaki, Materials Transactions 52,(2011) 127-129.

RESULTS: Voids removed their top surfaces were observed on the relatively large mass ions (Ge and Pb) irradiated wafer surfaces, and they were scarcely formed thesmall mass ions (Si and Al) irradiated surfaces.
In the case of Pb with the largest atom mass (207.2), thediameter of voids was widely distributed from 10 nm 300 nm. The density of voids with a diameter of 100 nm
and over are 4.4/1 m2, and they are formed by coalesceof neighboring voids (these void diameters are less thanabout 100 nm), consequently, the maximum diameter ofindividual voids is 100 nm at most.
Most of the voids observed in Ge (atomic mass =72.64)

採択課題番号 26P6-14
化合物半導体のイオンビーム照射効果（高知工科大・環境）新田紀子、谷脇雅文（京大・原子炉）徐 虬、義家敏正
34

プロジェクト