Transmission ERDA in Air with 15 MeV 4He Ions
Ryoya ISHIGAMI, Yoshifumi ITO, Keisuke YASUDA, Masato SASASE and
Satoshi HATORI
The Wakasa Wan Energy Research Center, 64-52-1 Nagatani, Tsuruga, Fukui 914-0192, JAPAN
Abstract. In-air transmission ERDA analysis was demonstrated using 15 MeV 4He beam in the W-MAST in Japan. The
4
He beam was extracted into air through a molybdenum foil with thickness of 5 mm. The diameter of the 4He beam was
about 2 mm after penetration through the foil. Titanium hydride TiHx and titanium deuteride TiDx with thicknesses of 2 mm
were analyzed by transmission ERDA at detection angles y=0° and y≈20°. The samples were placed at a distance from d=
1.8, 7.3, 12.8 and 15.8 cm from the foil. The estimated values x of the TiHx and TiDx were 0.95±0.2 for TiHx, 1.5±0.2 for
TiDx in case of d<10 cm, and 0.95±0.3 for TiHx, 1.5±0.4 for TiDx in case of d>10 cm.
INTRODUCTION
mostly data reported so far. Some data, being not found
elsewhere and being needed, were determined
experimentally.
Experiments using ion beam for element analysis
such as RBS, ERDA, NRA, PIXE have usually been
performed in vacuum. Many experiments of RBS and
PIXE in air were also carried out, where the samples
for the analysis were biological cells, works of art,
archaeological artefacts, etc which were not permitted
to be put in vacuum [1]. Recently, Calligaro et al.
reported ERDA experiments in helium gas at
atmospheric pressure [2]. As well known, ERDA has
been widely used as one of the most important tool in
the measurement of the hydrogen isotopes in the
materials nondestructively. It is expected that ERDA in
air is developed because of not only easy handling but
also of increase of the applicable targets.
In ERDA in air, heavy ion beams with high energy
are required because of suitable length of the beam
range after the extraction to air. Helium-4 ions with
energy of 15 MeV are available for material analysis at
the Wakasa Wan Energy Research Center [3]. We have
already developed the transmission ERDA method for
the deuterium detection in thick titanium foils using the
15 MeV 4He beams in vacuum [4].
In this report, development of transmission ERDA
in air is treated. As far as authors know, there is no
study of such method. We focused here on the
determination of concentrations of hydrogen and
deuterium in titanium foils using the transmission
ERDA in air. In the research, the differential recoil
cross-sections are essentially important. We used
EXPERIMENTAL PROCEDURE
Two samples of titanium hydride (TiHx) and
titanium deuteride (TiDx) foils were prepared by means
of the following procedure for in-air transmission
ERDA experiment. Titanium foils with thickness of 2
mm were placed in hydrogen or deuterium gas at a
pressure of 1 atmosphere for one hour at a temperature
of about 400°C. In the samples prepared by the above
procedure, TiHx and TiDx with 0<x<2 were formed.
ERDA experiment was carried out at the beam line
of irradiation room 2 in W-MAST facility [3]. Figure 1
(a) shows a schematic drawing of the experimental
setup. Helium-4 beam with energy of 15 MeV and
beam current of 15~35 nA are introduced into a
vacuum chamber after passing two apertures of 1 mm
in diameter, where the distance between the apertures
is 135.5 cm. The helium beam, passing through an
annular detector with a hole of 4 mm in diameter
(ORTEC, TC-017-050-300) mounted in the center of
the chamber, is extracted into air through the window
of the thin foil. A detailed drawing of the sectional
view of the extraction portion is shown in Fig. 1 (b). A
gold (Au) film with thickness of 0.45 mm was
deposited on a surface of a molybdenum (Mo) foil with
thickness of 5 mm. The Mo foil with the Au film is
used as the extraction window, where the Au film faces
CP680, Application of Accelerators in Research and Industry: 17th Int'l. Conference, edited by J. L. Duggan and I. L. Morgan
© 2003 American Institute of Physics 0-7354-0149-7/03/$20.00
474
(a)
1355 mm
460 mm
425 mm
ERDA
Detector
d (cm)
15 MeV 4He2+ ions
y≈20°
Aperture
f1 mm
Aperture
f1 mm
Sample
24.8-d (cm)
4
Vacuum Chamber
Carbon pipe
12
9
f2
f30 f10
Annular Detector
36
(b)
24.8-d (cm)
f3
f3
Gold film deposited
on Molybdenum foil
10
Copper pipe
FIGURE 1. A schematic drawing of (a) the experimental apparatus and (b) a section of a copper pipe. The 4He beam was
extracted through the copper pipe. The unit in the figure (b) is the millimeter. The pipe also played a role as a gasket of 48 mm in
outside diameter.
The detection angles y in the transmission ERDA
were chosen to be 0°, 16.6°, 19.4°, 20.0° and 20.6°. A
detector for ERDA was located so that a distance
between the sample and the detector was 24.8-d cm.
Accuracy of the positions of the sample and the
detector was within ±2 mm.
A copper sheet of 1 mm in thickness with an
aperture of 5 mm in diameter was placed in front of the
detector. Energy resolution (FWHM) of the detector
together with the electronic circuit was estimated to be
40 keV from energy measurement of a particles
emitted from 241Am.
to the inside of the chamber. Note that usual RBS
analysis is acceptable when 4He ions with energy of
~15 MeV are scattered by Au target at the scattering
angle of ~180° [5]. Number of 4He ions scattered
backward by the Au was used for the determination of
number of 4He ions extracted into air. For the
elimination of the RBS signals of 4He scattered by
copper, a carbon pipe is inserted inside the copper pipe.
The numbers of 4He ions scattered by the Au film were
measured by use of the annular detector with the active
area of 22.7 mm2. The distance between the Au film
and the annular detector is 460 mm and the solid angle
of detection is 1.07x10-4 str. The number of the 4He
ions extracted into air was found to be (2.7~6.5)x1013
ions during 600 seconds.
The sample of TiHx or TiDx foil is mounted on an
aluminum plate with a hole of 17 mm in diameter at
the distance d from the extraction window of the Mo
foil. The mean energy of the 4He ions after penetration
through the Mo foil was estimated to be 13.94 MeV.
The values d in Fig. 1 (a) were determined to be 1.8,
7.3, 12.8 and 15.8 cm, since the range of 4He ion with
energy of 13.94 MeV in air is about 20 cm. The
energies E of the 4He ions incident to the sample at
these positions were 13.18 MeV, 10.61 MeV, 7.46
MeV, and 5.27 MeV, respectively. Here, the energies
were calculated by use of the stopping power formulae
given by Ziegler [6].
RESULTS AND DISCUSSION
Figure 2 shows energy spectra obtained for the
samples of (a) TiHx and (b) TiDx foils, where the
distance d=7.3 cm and the detection angle y=20.0°.
The energy spectrum obtained for (c) a titanium (Ti)
foil with thickness of 2 mm is also plotted. Here, each
spectrum is normalized from the numbers of the 4He
ions incident on the sample. Energies at peak value in
the spectra of (a) and (b) are 4.69 MeV and 6.73 MeV,
which correspond to the mean energies of proton and
deuteron recoiled by the 4He with energy of 10.61
MeV at the angle of 20.0°, being attenuated in the
samples and in air. The energy spectrum caused of
protons ( or deuterons ) recoiled by the 4He ions was
475
Counts / ch /10 12 4He2+ ions
400
Position d = 7.3 cm
Detection Angle y = 20.0o
300
experimentally. Finally, absolute values of the crosssections at f=0° were found from the polynomials and
experimental values. The detail description of the
cross-section determination will be reported elsewhere.
Here, only the values of the cross-section used here are
listed in Table 1.
The densities of hydrogen and deuterium in the
samples were obtained on the assumption that the
hydrogen and deuterium were uniformly distributed in
the titanium foils. The values x in TiHx and TiDx were
found when the atomic density of metallic titanium
was 5.658x1022 cm-3. Figure 3 shows the values x
plotted for the samples of (A) TiHx and of (B) TiDx,
where distance d in Fig. 1 (a) is used as a parameter in
horizontal axis. The errors in x were evaluated from
many factors; accuracy of the positions of the samples
and the detector, error of the differential recoil crosssections, and errors due to the numbers of detected
protons and deuterons, and due to the counts of the
background. The values x are scattered around 0.95 for
(A) TiHx and around 1.5 for (B) TiDx. The scatter of the
estimated values becomes large with the distance d.
The values x for the measurements at a detection angle
y=0° are smaller than those at angles y≈20°
systematically in both cases of (A) TiHx and of (B)
TiDx. This means that a systematic error was included
(a) TiHx
(b) TiD x
(c) Ti
(a)
200
(b)
100
(c)
0
0
2
4
6
8
10
12
Energy (MeV)
FIGURE 2. Typical ERDA spectra obtained in the
transmission geometry. The samples were (a) TiHx, (b) TiDx
and (c) Ti foils. The distance d from the Mo foil to the
samples is 7.3 cm, and the detection angle is y = 20.0°.
found, after the subtraction of the value (background
noise) obtained for the Ti foil. Total counts due to the
recoiled protons (or deuterons) could yield the
concentrations of hydrogen (or deuterium) in the TiHx
(or TiDx) foil, being taken into account of the
differential recoil cross-sections of proton (or
deuteron) by the 4He as the projectile.
The 4He beam incident into the sample suffered
slight spread in the lateral direction caused by the
multiple scattering in the Mo foil and in air.
Modification in the beam intensity on the sample with
diameter of 17 mm at a distance d=1.8, 7.3, 12.8 and
15.8 cm from the Mo foil was calculated to be 1.0, 1.0,
0.987 and 0.921, respectively. The detail description
about the calculation method of the angular spread of
ion beams can be found in reference 4.
In the determination of the concentrations of
hydrogen and deuterium, the differential recoil crosssections of proton and deuteron by 4He were required,
where the energies E0 of the 4He were 13.18, 10.61,
7.46 and 5.27 MeV and the recoil angles f were 0°,
16.6°, 19.4°, 20.0° and 20.6°. The cross-section data
available in these energy and recoil angle regions are
listed in Table 1. There are many cross-section data in
the region of the energy E0 =3~16 MeV and of the
recoil angle f=10~25°. However, there are a few recoil
cross-sections of proton at f=0°, and no data of
deuteron at f≈0° and E0=9~15 MeV. The crosssections needed here were determined as the following
procedure. Firstly, the recoil cross-sections at f≈20°
were expressed as polynomials of high degrees with
two independent variables, f and E0 by the fitting of
the data reported so far using the least squares.
Secondly, ratios of the recoil cross-sections of proton
and deuteron at f=0° to those at f=17.8° were obtained
TABLE 1. The values of differential recoil cross-sections of
(a) proton and (b) deuteron by 4He used in the determination
of the concentrations of hydrogen and deuterium in the
samples. References in which the cross-section data
available in this experiment are reported are written in the
square brackets.
(a) TiHx
d (cm)
1.8
7.3
12.8
15.8
E0(MeV)
13.18
10.61
7.46
5.27
ds (b/str) 1.00±0.04 1.70±0.04 1.48±0.09 0.70±0.05
df
f (°)
0
0
0
0
[References 7, 8 (E0£8 MeV, f=0°)]
ds (b/str) 0.64±0.04 1.03±0.02 0.94±0.04 0.55±0.03
df
f (°)
19.4
20.0
20.6
16.6
[References 7, 9 (10°£f<25°)]
(b) TiDx
d (cm)
1.8
7.3
12.8
15.8
E0(MeV)
13.18
10.61
7.46
5.27
ds (b/str) 1.12±0.02 1.51±0.03 0.76±0.06 0.40±0.01
df
f (°)
0
0
0
0
[Reference 10 (E0£9 MeV, f=3.2°)]
ds (b/str) 0.46±0.01 0.63±0.01 0.48±0.01 0.38±0.01
df
f (°)
19.4
20.0
20.6
16.6
[References 11 (10°£f<25°)]
476
4
1.6
(a) Hydrogen
1.4
He beam after penetration through the foil was about 2
mm. The measurements were performed at detection
angles y=0° and y≈20°. The samples were placed at a
distance of d=1.8, 7.3, 12.8 and 15.8 cm from the Mo
foil. The estimated values x of the TiHx and TiDx were
0.95±0.2 for TiHx, 1.5±0.2 for TiDx in case of d<10 cm,
and 0.95±0.3 for TiHx, 1.5±0.4 for TiDx in case of d>10
cm.
y = 0°
y ≈ 20°
x in TiH x
1.2
1.0
0.8
0.6
0.4
0.2
ACKNOWLEDGEMENTS
0.0
0
5
10
15
20
The authors would like to thank Y. Hayashi, M.
Yamada, H. Yamada, J. Mori, S. Kimura and T. Hamaji
for their operation of accelerators at W-MAST through
the experiment.
Distance from the Mo foil (cm)
2.5
y = 0°
y ≈ 20°
(b) Deuterium
x in TiD x
2.0
REFERENCES
1.5
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631-634.
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(2002).
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Meth. B51, 311-319 (1990).
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66-69.
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10.Galonsky, A. et al., Phys. Rev. 98, 586-591 (1955).
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Phys. Rev. 75, 1678-1680 (1949); Mani, G. S., and Tarratts,
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1.0
0.5
0.0
0
5
10
15
20
Distance from the Mo foil (cm)
FIGURE 3. The values x in the (A) TiHx and (B) TiDx
plotted vs distance d between the Mo foil and the samples.
in the determination of the concentration. The average
counting rate in the particle detection at a detection
angle y=0° was about 3.2 kc/s at maximum and that at
detection angles y≈20° was less than 2.4 kc/s at
maximum. No counting loss seems to occur even in the
case at the angle y=0°. The reason of the scatter of the
estimated values is not clear, so further investigation
for the reduction of inaccuracy will be needed.
It was concluded that the x estimated using the
transmission ERDA were 0.95±0.2 for TiHx, 1.5±0.2
for TiDx in case of d<10 cm, and 0.95±0.3 for TiHx, 1.5
±0.4 for TiDx in case of d>10 cm.
CONCLUDING REMARKS
The titanium hydride TiHx and titanium deuteride
TiDx with thickness of 2 mm were analyzed by means
of ERDA method with 15 MeV 4He beam in air in
transmission geometry. The 4He beam was extracted
into air through a Mo foil with thickness of 5 mm. The
beam intensity extracted into air was determined from
the analysis of the 4He scattered backward by a gold
thin film deposited on the Mo foil. The diameter of the
477