Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 53

Activation-cross-section measurement of alpha-induced reactions onnatural dysprosium
T. Murata,∗1,∗2 M. Aikawa,∗1,∗2,∗3 M. Sakaguchi,∗1,∗2 H. Haba,∗2 Y. Komori,∗2 Z. Szűcs,∗4 F. Ditrói,∗4 andS. Takács∗4
Holmium-166 can be used for a liver-cancer treatment
called radioembolization.1) It is worthwhile to investigate the most eﬃcient method for 166 Ho production bycomparing possible production reactions. The alphainduced reaction on dysprosium is one of them. However, there are no available experimental data for thisreaction. Thus, we were motivated to perform an experiment for the nat Dy(α, x)166 Ho reaction.
The experiment was performed using the AVF cyclotron at the RIKEN Beam Factory (Wako, Saitama,Japan). The stacked-foil activation technique and highresolution γ-ray spectrometry were used to measure thecross sections of generated radionuclides. The stackedfoil target consisted of natural dysprosium (99% purity,Goodfellow Co., Ltd., UK) and natural titanium (99.6%purity, Nilaco Corp., Japan). The sizes and weightsof both foils were measured, and the derived average
thicknesses of the natural dysprosium and natural titanium foils were 23.6 µm and 5.1 µm, respectively. Bothfoils were cut into pieces of 8 × 8 mm2 size and inserted into the target holder, which served as a Faradaycup. The target was irradiated with a 50.6-MeV alphabeam. The measured beam intensity was 103.8 pnA.
The beam energy was measured using the time-of-ﬂight(TOF) method.2) The energy degradation in the target
was calculated using the stopping powers obtained fromSRIM code.3)
After one-hour irradiation, the target was removed
from the target holder for oﬀ-line γ-ray spectrometry

Fig. 1. Comparison of the excitation function of thenatTi(α, x)51 Cr monitor reaction with IAEA’s recommended values.4)
∗1
∗2
∗3
∗4

Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Faculty of science, Hokkaido Unviersity
Institute for Nuclear Research, Hungarian Academy of Sciences (ATOMKI)

Fig. 2. Comparison of the excitation function of thenatDy(α, x)166 Ho reaction with the TENDL-2017 data.5)

using a high-purity germanium (HPGe) detector. The
320.08-keV γ-line (T1/2 = 27.704 d, Iγ = 9.91%) wasused to derive the cross sections of the nat Ti(α, x)51 Crmonitor reaction.
Because the cross sections of the monitor reaction
were signiﬁcantly diﬀerent from IAEA’s recommendedvalues,4) an elemental analysis of the dysprosium foil wasconducted via scanning electron microscopy with energy
dispersive spectroscopy (SEM-EDS) using JSM-6610LA
with JED-2300, JEOL Ltd. at Hokkaido Research Organization. The foil was found to contain 4.27% oxygenby mass. The stopping power of natural dysprosium wasmodiﬁed by considering the oxygen compounds. Consequently, the excitation function of the nat Ti(α, x)51 Crreaction showed good agreement with the recommendedvalues4) as shown in Fig. 1. The beam intensity wascorrected by −4% from the measured one.
The γ-line of 80.576 keV (T1/2 = 26.824 h, Iγ =6.56%) was used to derive the excitation function ofthe nat Dy(α, x)166 Ho reaction. The result is shown inFig. 2 with the TENDL-2017 data.5) It was found thatthe TENDL-2017 data5) signiﬁcantly underestimate thecross sections of this reaction.
The production of the radioactive by-products, suchas 167 Ho (T1/2 = 3.003 h), is being analyzed. The results
will be published in a forthcoming paper.
References

1) M. Reinders et al., Semin. Nucl. Med. 49, 237 (2019).
2) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC2014), (2014), p. 3566.
3) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res. B
268, 1818 (2010).
4) A. Hermanne et al., Nucl. Data Sheets 148, 338 (2018).
5) A. J. Koning et al., Nucl. Data Sheets 113, 2841 (2012).

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