Ⅲ-3. Radiochemistry & Nuclear Chemistry
RIKEN
Accel. Prog. Rep. 56 (2023)

RIKEN Accel. Prog. Rep. 56 (2023)

Production cross sections of 189g Ir in α-particle-induced reactions onnatReG. Damdinsuren,∗1,∗2 M. Aikawa,∗1,∗2,∗3 S. Ebata,∗4,∗2 H. Haba,∗2 S. Takács,∗5,∗2 F. Ditrói,∗5,∗2 andZ. Szücs∗5,∗2

∗1
∗2
∗3∗4
∗5Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Faculty of Science, Hokkaido University
Graduate School of Science and Engineering, Saitama University
Institute for Nuclear Research (ATOMKI)- 181 -and analyzed using dedicated software (SEIKO EG&GGamma Studio). The spectra of each nat Re foil andthe following 27 Al catcher foil were measured severaltimes. The distance between the detector and the foils
was set to keep dead time below 1%.
To assess the beam parameters and target thicknesses, the nat Ti(α, x)51 Cr monitor reaction cross sections were derived. The γ line at 320.08 keV (Iγ =9.910%) from the decay of 51 Cr (T1/2 = 27.7025 d)
was measured after a cooling time of 2 d.
The derived cross sections were compared with theIAEA-recommended values.8) Based on the comparison, the incident beam energy and thickness of thenat
Re foil were corrected within the uncertainties by+0.2 MeV and −1%, respectively.
The measurement of the γ line at 245.1 keV (Iγ =6.0%) emitted with the decay of 189g Ir was performed
after a cooling time of 36 d. The two short-lived
excited states with shorter half-lives (T1/2 = 13.3
and 3.7 ms, IT: 100%) decayed to 189g Ir during theirradiation. The cumulative cross sections of thenatRe(α, x)189g Ir reaction were derived from measured
net counts. The preliminary result of the cross sectionsof 189(g+m1+m2) Ir is shown in Fig. 1, together with theprevious experimental data2–4) and the TENDL-2021
values.5) The experimental data of Singh and Gadkari4) are higher than our data, while the peak position is located at nearly the same energy. The dataof Goncharov et al.2) and Ismail3) are largely diﬀerent
from ours in both peak amplitude and position. TheTENDL-2021 values agree well with ours.
800

Cross section [mb]Iridium-189 has the ground state 189g Ir (T1/2 = 13.2d, ε: 100%) and two short-lived excited states 189m1 Irand 189m2 Ir (T1/2 = 13.3 and 3.7 ms, IT: 100%). The
radionuclide 189g Ir is an Auger electron emitter and canbe used for therapy in nuclear medicine.1) Chargedparticle-induced reactions on osmium and rhenium arepossible production routes of 189g Ir. In this work, wefocused on the α-particle-induced reactions on nat Retargets. In a literature survey, three experimental
studies of the cross sections of the nat Re(α, x)189 Ir
reactions were found.2–4) The previous experimental
data are signiﬁcantly diﬀerent in peak position andamplitude. Therefore, we performed an experiment tomeasure reliable cross sections of the nat Re(α, x)189 Ir
reaction. The result was compared with the experimental data published earlier and the TENDL-2021
values.5)
The experiment was conducted at the AVF cyclotronof the RIKEN RI Beam Factory. The stacked-foil technique, activation method, and high-resolution γ-ray
spectrometry were used. The stacked target consistedof pure metallic foils of nat Re (12.5-µm thick, 99.99%purity), nat Ti (5-µm thick, 99.6% purity), and 27 Al (5µm thick, 99.9% purity). All foils were purchased from
Nilaco Corp., Japan. The nat Ti foils were used for thenatTi(α, x)51 Cr monitor reaction. The 27 Al foils wereinserted to catch reaction products recoiled from thenat
Re and nat Ti foils. The target thicknesses were derived from the measured size and weight of the foils.
The derived thicknesses of nat Re, nat Ti, and 27 Al foils
were 25.3, 2.24, and 1.22 mg/cm2 , respectively. The
original foils were then cut into a size of 10 × 10 mm
to ﬁt in a target holder that served as a Faraday cup.
Fifteen sets of Re-Al-Ti-Al foils were stacked in thetarget holder.
The stacked target was irradiated with a 50.6 ±0.2 MeV α-particle beam for 30 min. The primary beam energy was measured by the time-of-ﬂight
method.6) Energy degradation in the stacked target
was calculated using stopping powers derived from theSRIM code.7) The average beam intensity measured bythe Faraday cup was 203 nA.
The γ-ray spectra were measured using a highresolution HPGe detector (ORTEC GEM-25185-P)

700

natRe(α,x)189(g+m1+m2)Ir600

Ismail (1993)
Singh (2004)
TENDL-2021
This work

500
400
300
200
100001020304050

Energy [MeV]Fig. 1. Cumulative cross sections of the nat Re(α, x)189g Ir
reaction.

The analyses to determine the ﬁnal cross sections ofIr and other co-products are continued. The thick189g

Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 56 (2023)

target yields of the products can be calculated using
the measured cross sections. The ﬁnalized results areexpected to contribute to the practical use of radionuclides in nuclear medicine.
G. Damdinsuren was granted a scholarship by theM-JEED project (Mongolian-Japan Engineering Education Development Program, J11B16).
References
1) D. Filosofov et al., Nucl. Med. Biol. 94, 1 (2021).
2) K. S. Goncharov et al., Sov. J. Nucl. Phys. 32, 319(1980).
3) M. Ismail, Pramana - J. Phys. 40, 227 (1993).
4) N. L. Singh et al., Can. J. Phys. 82, 227 (2004).
5) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
6) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC 2014), (2014), p. 3566.
7) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res.
B 268, 1818 (2010).
8) F. Tárkányi et al., IAEA-TECDOC-1211 (2007).

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