Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 52 (2019)

Activation cross sections of alpha-induced reactions on nat In for117m
Sn production†
M. Aikawa,∗1,∗2 M. Saito,∗3,∗2 N. Ukon,∗4,∗2 Y. Komori,∗2 and H. Haba∗2†∗1
∗2
∗3
∗4

Condensed from the article in Nucl. Instrum. Methods Phys.
Res. B 426, 18 (2018)
Faculty of Science, Hokkaido University
RIKEN Nishina Center
Graduate School of Biomedical Science, Hokkaido University
Fukushima Global Medical Science Center, Fukushima Medical University- 192 -200Cross section (mb)The radioisotope 117m Sn (T1/2 = 13.76 d) can beused as a theranostic radioisotope for both medical
therapy and imaging. The production of 117m Sn isof much concern, and the possible production reactions are studied. We focused on one of the reactions,
namely the 115 In(α, x)117m Sn reaction, in this paper.
Three experimental literature1–3) could be found in theEXFOR library.4) The literature data, however, show alarge discrepancy from each other. More reliable andaccurate data are required for practical use. Therefore, we performed a new experiment to measure thecross sections of the 115 In(α, x)117m Sn reaction. In addition, the cross sections of the by-products, 113 Sn and116m, 117, 118m
Sb, were measured.
The experiment was performed at the AVF cyclotronof the RIKEN RI Beam Factory. The stacked foil
technique, activation method, and high resolution γray spectrometry were used to derive the activation
cross sections. Metallic foils of nat In (4.29% 113 Inand 95.71% 115 In) and nat Ti were stacked as a target.
The target was irradiated by a 51.6-MeV α beam for
2 h. The incident beam energy was determined using
the time-of-flight method.5) The beam energy degradation in the stacked target was calculated using theSRIM code.6) The average intensity of the beam was
202.1 nA, which was measured by a Faraday cup. The
irradiated foils were separated and subjected to γ-ray
spectrometry with an HPGe detector.
The excitation function of the nat Ti(α, x)51 Cr monitor reaction was used to assess the beam parameters and the target thicknesses. The excitation function could be derived from measurements of the γ line
at 320.08 keV (Iγ = 9.91%) from the decay of 51 Cr(T1/2 = 27.7025 d). The result is in good agreementwith the recommended values.7) Therefore, we adopted
the measured beam parameters and target thicknesses
without any adjustments.
The measurement of the 156.02-keV γ line (Iγ =2.113%) from the 117m Sn decay was performed for thecross sections of the 115 In(α, x)117m Sn reaction. The
cooling time was longer than 45 h for the complete
decay of the parent nuclei, 117g In (T1/2 = 43.2 min),
117mIn (T1/2 = 116.2 min), and 117 Sb (T1/2 = 2.80 h).
The cumulative cross sections of 117m Sn for nat In targets were obtained from the measurement. The cross

115In(α,x)117mSn150

Fukushima+ (1963)
Qaim+ (1984)
Bhardwaj+ (1992)
TENDL2017
This work

100

5001015202530 35 40
Energy (MeV)

455055

Fig. 1. Excitation function of the 115 In(α, x)117m Sn reaction.

sections were normalized to those for 115 In enrichedtargets, taking into account the negligibly small contribution of the α-capture reaction on 113 In. The resultis shown in Fig. 1 in comparison with the previous experimental data1–3) and the TENDL-2017 data.8) The
present result is almost consistent with the data obtained by Qaim and Döhler (1984).2) The data obtained by Fukushima et al. (1963)1) and TENDL-2017
show smaller amplitudes than the others. On the contrary, the data obtained by Bhardwaj et al. (1992)3)
are much larger than that obtained by the others.
In this work, the cross sections of the 115 In(α,117m
Sn reaction up to 50 MeV were measured usx)
ing the stacked foil activation technique and high resolution γ-ray spectrometry. The measured cross sections were compared with the earlier experimental data
and the TENDL data. One of the three experimental
datasets is in good agreement with our result. Our
result can contribute to the estimation of 117m Sn production.
References
1) S. Fukushimai et al., Bull. Chem. Soc. Jpn. 36, 1225
(1963).
2) S. M. Qaim et al., Int. J. Appl. Radiat. Isot. 35, 645(1984).
3) M. K. Bhardwaj et al., Int. J. Mod. Phys. E 1, 389(1992).
4) N. Otuka et al., Nucl. Data Sheets 120, 272 (2014).
5) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC2014), 3566 (2014).
6) SRIM: the Stopping and Range of Ions in Matter, http://www.srim.org/.
7) A. Hermanne et al., Nucl. Data Sheets 148, 338 (2017).
8) A. J. Koning, D. Rochman, Nucl. Data Sheets 113, 2841
(2012).