III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Production cross-sections of dysprosium-159 radioisotope obtained by
α-particle-induced reactions of natural gadolinium up to 50 MeV†
D. Ichinkhorloo,∗1,∗2,∗3 M. Aikawa,∗1,∗4,∗3 Ts. Zolbadral,∗4,∗2,∗3 T. Murata,∗4,∗3 M. Sakaguchi,∗4,∗3 Y. Komori,∗3T. Yokokita,∗3 and H. Haba∗3Dysprosium and terbium radioisotopes are of interest for diagnosis and therapy in nuclear medicine.
Dysprosium-157 (T1/2 = 8.14 h), dysprosium-159 (T1/2= 144.4 d), and terbium-155 (T1/2 = 5.32 d) can be used
for bone scanning (skeletal imaging),1) determination ofbone mineral,2) and single-photon emission computerized tomography imaging,3) respectively.
Radionuclides can be produced in natural gadoliniumby charged-particle-induced reactions. In this study, theactivation cross-sections of α-particle-induced reactionsin natural gadolinium were investigated. Production
cross-sections of 155, 157, 159 Dy, 153, 155, 156g, 160, 161 Tb,and 153 Gd were determined. The results were comparedwith TENDL-2019 data based on TALYS code calculation.4)
Experiments were conducted at the RIKEN AVF cyclotron, which in the stacked foil technique, the activation method and the high-resolution γ-ray spectrometry
to determine the activation cross-sections.
A stacked target was formed of 8 × 8 mm2 foils cut
from large Gd (25 μm, 50×50 mm2 , 99.9% purity, NilacoCorp., Japan) and Ti foils (5 μm, 50 × 100 mm2 , 99.6%purity, Nilaco Corp., Japan). The isotopic composition of the natural Gd target was 152 Gd (0.2%), 154 Gd(2.2%), 155 Gd (14.8%), 156 Gd (20.5%), 157 Gd (15.6%),
158
Gd (24.8%), and 160 Gd (21.9%).
The sizes and weights of the large foils were measured
to derive the thicknesses of the Gd and Ti foils, whichwere found to be 25.4 and 2.29 mg/cm2 , respectively.
The Ti foils were used in the nat Ti(α, x)51 Cr monitor reaction to assess beam parameters and target thicknesses.
The cut foils were stacked into the target holder, which
was used as a Faraday cup.
An α-particle beam was accelerated to 51.1 MeV bythe RIKEN AVF cyclotron. The beam energy was obtained using the time-of-ﬂight method.5) The stacked
target was irradiated by the beam for 60 min with anaverage intensity of 257.6 nA. The beam intensity wasmeasured using the Faraday cup. Energy degradation in
the stacked target was calculated using the SRIM code.6)
The γ rays emitted from the irradiated foils were measured by a high-resolution high-purity germanium detector.
The γ-ray spectra were analyzed with the Gamma†∗1
∗2
∗3
∗4
∗5

Condensed from the article in Nucl. Instrum. Methods Phys.
Res. B 499, 46 (2021)
Faculty of Science, Hokkaido University
Nuclear Research Center, National University of Mongolia
RIKEN Nishina Center
Graduate School of Biomedical Science and Engineering,
Hokkaido University
School of Science, Hokkaido University

Fig. 1. Excitation function of the nat Gd(α, x)159 Dy reaction
compared to TENDL-2019 data.4)

Studio (SEIKO EG&G) software.
The cross-sections of the nat Gd(α, x)159 Dy reaction
were determined using the γ-ray line at 58.0 keV (Iγ =2.27%) from the 159 Dy decay (T1/2 = 144.4 d). To reduce the γ-ray background from the short-lived radionuclides, the measurements were executed after coolingtimes of 25.4–28.8 d. The mass attenuation coeﬃcient
adopted for the γ-ray line at 58.0 keV was 12.8 cm2 /g.7)
The correction factor using Eq. (1) of Ref. 8) is 1.17. The
cross-sections of the 159 Dy production derived from thecorrected activities are presented with the TENDL-2019
data4) in Fig. 1. Our experimental data show peaks at
approximately 35 and above 50 MeV. The peak amplitudes and positions in the TENDL-2019 data agree withour results. Reported experimental data were no foundin our literature survey.
155, 157
Dy,
Production
cross-sectionsof153, 155, 156g, 160, 161
153
Tb, andGd were also determined.
The results of this study are expected to contribute to
the research and development of nuclear medicine.
References
1) G. Subramanian et al., J. Nucl. Med. 12, 558 (1971).
2) D. V. Rao et al., Med. Phys. 4, 109 (1977).
3) C. Müller et al., J. Nucl. Med. 53, 1951 (2012).
4) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
5) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(2014), p. 3566.
6) J. F. Ziegler et al., SRIM: the Stopping and Range of Ionsin Matter, http://www.srim.org .
7) Photon Interaction Database, National Institute of Standards and Technology (2004), https://physics.nist.
gov/PhysRefData/XrayMassCoef/tab3.html .
8) Z. B. Alfassi et al., Appl. Radiat. Isot. 67, 240 (2009).

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