Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 53

Production cross sections of 157 Dy in alpha-particle-induced reactions
on natural gadolinium
D. Ichinkhorloo,∗1,∗2,∗3 M. Aikawa,∗1,∗4,∗3 Ts. Zolbadral,∗4,∗2,∗3 T. Murata,∗4,∗3 M. Sakaguchi,∗4,∗3Y. Komori,∗3 T. Yokokita,∗3 and H. Haba∗3
The radioisotope dysprosium-157 (T1/2 = 8.14 h)
can be used for bone scanning (skeletal imaging).1)
This radionuclide can be produced through chargedparticle-induced reactions on natural gadolinium. In
this work, the production cross sections of 157 Dy in thealpha-particle-induced reactions on natural gadolinium
were studied. No previous experimental data were
found in a literature survey. The results were compared with TENDL-2017 data.2)
The experiment was performed at the RIKEN AVF
cyclotron. In the experiment, we used the stacked foil
technique, the activation method, and high-resolution
γ-ray spectrometry to determine the activation crosssections.
The stacked target consisted of 8 × 8 mm2 foils cut
from a larger Gd foil (25 µm, 50 × 50 mm2 , 99.9%
purity, Nilaco Corp., Japan) and Ti foils (5 µm, 50 ×100 mm2 , 99.6% purity, Nilaco Corp., Japan). The
isotopic composition of the natural Gd target is 152 Gd(0.2%), 154 Gd (2.2%), 155 Gd (14.8%), 156 Gd (20.5%),
157
Gd (15.7%), 158 Gd (24.8%), and 160 Gd (21.8%).
The sizes and weights of the larger foils were measured to derive the average thickness. The thicknessof the Gd and Ti foils were found to be 25.4 and2.29 mg/cm2 , respectively. The Ti foils were used toassess beam parameters and target thicknesses usingthe nat Ti(α, x)51 Cr monitor reaction. The cut foils
were stacked in a target holder, which also served as aFaraday cup.
The alpha-particle beam was accelerated to51.1 MeV by the RIKEN AVF cyclotron.
Thebeam energy was measured using the time-of-ﬂight
method.3) The stacked target was irradiated for 60 min
with an average beam intensity of 257.6 nA. The beam
intensity was measured using the Faraday cup. Energy
degradation in the stacked target was calculated using
SRIM code.4)
The γ-rays emitted from the irradiated foils weremeasured using a high-resolution high-purity germanium (HPGe) detector. The γ-ray spectra were analyzed using the software Gamma Studio (SEIKOEG&G). The γ-rays at 326.3 keV (Iγ = 93%) emitted
after the decay of 157 Dy (T1/2 = 8.14 h) was measured
to derive the cross sections of the nat Gd(α, x)157 Dy
∗1
∗2
∗3
∗4
∗5

Faculty of Science, Hokkaido University
Nuclear Research Center, National University of Mongolia
Nishina Center for Accelerator-Based Science, RIKEN
Graduate School of Biomedical Science and Engineering,
Hokkaido University
School of Science, Hokkaido University- 187 -Fig. 1. Excitation function of the nat Gd(α, x)157 Dy reaction.

reaction. The measurements were performed after acooling time of 15 h.
The total uncertainties (8.8%) were estimated fromthe square root of the quadratic summation of eachcomponent: statistical uncertainty (1.5%), target
thickness (2%), target purity (1%), beam intensity(5%), detector eﬃciency (6%), and γ -ray intensity(3.2%).
The cross sections derived from the activity of 157 Dy
are presented in comparison with TENDL-2017 data2)
in Fig. 1. The TENDL-2017 data underestimate ourexperimental cross sections.
In summary, we have performed an experiment tomeasure the activation cross sections of alpha-particleinduced reactions on nat Gd up to 51 MeV at theRIKEN AVF cyclotron. In this work, the production
cross sections of 157 Dy were determined, and the results were compared with the prediction of TALYSbased model calculation, for which data were takenfrom the TENDL-2017 online database.
This work was supported by JSPS KAKENHI Grant
Number 17K07004.
References1) G. Subramanian et al., J. Nucl. Med. 12, 558 (1971).
2) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
3) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC 2014), 3566 (2014).
4) J. F. Ziegler et al., SRIM: the Stopping and Range ofIons in Matter, http://www.srim.org .