Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 51 (2018)

Activation cross sections of α-induced reactions on nat In for 117m Snproduction
M. Aikawa,∗1,∗2 M. Saito,∗1,∗2 Y. Komori,∗2 and H. Haba∗2∗1∗2

Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center- 220 -

Table 1. Decay data for 117m Sn and related nuclei
Nuclide117m47

Sn

Sc

T1/2

Eγ (keV)Iγ (%)

13.76 d156.022.113

158.56

86.4

159.38168.3

3.3492 d200115

Cross section (mb)The radioisotope (RI) 117m Sn (T1/2 = 13.76d) decays with emission of both conversion electrons (126.82, 129.369, and 151.56 keV) and γ rays
(158.56 keV). Further, this RI can be used as a bone
pain palliation agent, because the electrons and γ rays
are appropriate for therapy and imaging, respectively.
The production reactions of this RI have previously
been investigated and discussed; however, their production in adequate quantities remains of much concern.1) In this study, we focused on one of the reactions,i.e., the 115 In(α,x)117m Sn reaction, the cross sectionsof which have exhibited large discrepancies in previousstudies.2–4) Another experiment measuring the crosssections of the reactions is, therefore, valuable.
The experiment was performed at the Azimuthally
Varying Field cyclotron of the RIKEN RI Beam Factory using well-established methods, e.g., the stacked
foil technique, activation method, and high-resolution
γ-ray spectrometry. Natural In foils (purity: 99.99%;Nilaco, Japan) were stacked with natural Ti monitor
foils (purity: 99.6%; Nilaco, Japan). The thicknessesof the In and Ti foils were estimated from the measured areas and weights of large foils (50 × 50 mm2 )and found to be 16.60 and 2.44 mg/cm2 , respectively.
The stacked target consisted of 11 sets of In-In-Ti-Ti
foils (8 × 8 mm2 ) cut from the large foils. The ﬁrst
foils on the downstream side of the beam were measured to compensate for the losses of the recoil products. However, the In foils were melted because of their
low melting point at 156.6◦ C and could not be separated after α beam irradiation. Each set of In foils
was therefore considered as one foil of 33.3 mg/cm2 .
Irradiation with a 51.6-MeV α beam with an averageintensity of 202.1 nA was performed for 2 h. The intensity and beam energy were measured by a Faraday-cuplike target holder and the time-of-ﬂight method using aplastic scintillator monitor.5) The γ rays emitted fromthe irradiated foils were measured by a high-resolution
high-purity Germanium detector.
The decay data6,7) are summarized in Table 1. Measurement of the 156.02-keV γ-line (Iγ = 2.113%) fromthe 117m Sn decay was performed after a cooling timeof approximately 45 h. The cooling time was set
to be suﬃciently long for decay of the parent nuclei,
117Sb (T1/2 = 2.80 h), 117g In (T1/2 = 43.2 min), and117m
In (T1/2 = 116.2 min). The γ-line at 158.56 keV(Iγ = 86.4%) was not selected to avoid the overlapped
contribution of the 159.377-keV γ-line (Iγ = 68.3%)

In(,x)

117m

Sn

150

Fukushima+ (1963)
Qaim+ (1984)
Bhardwaj+ (1992)
TENDL2015
This work

100500102030

405060

Energy (MeV)

Fig. 1. Excitation function of 115 In(α,x)117m Sn reaction.
The result is compared with previous experimentaldata2–4) and TENDL-2015.8)

from the 47 Sc (T1/2 = 3.3492 d) in the Ti catcher
foils. The 115 In(α,x)117m Sn reaction cross sections estimated from the 115 In abundance (95.71%) are shownin Fig. 1, together with the previous experimental data(open symbols)2–4) and the TENDL-2015 data (dashedline).8) Among the three sets of experimental data,
the present result (ﬁlled symbols) is consistent withQaim et al. (1984).3) More detailed analysis regarding
117m
Sn and other RIs is currently being performed.
References
1) T. Das, S. Banerjee, Clin. Exp. Metastasis 34, 1 (2017).
2) S. Fukushima et al., Bull. Chem. Soc. Jpn. 36, 1225
(1963).
3) S. M. Qaim, H. Döhler, Int. J. Appl. Radiat. Isot. 35,645, (1984).
4) M. K. Bhardwaj et al., Int. J. Mod. Phys. E 1, 389(1992).
5) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC2014), (2014), p.3566.
6) National Nuclear Data Center, The NuDat 2 database,
http://www.nndc.bnl.gov/nudat2/.
7) S. Y. F. Chu et al., The Lund/LBNL nuclear data
search, http://nucleardata.nuclear.lu.se/toi/.
8) A. J. Koning et al., TENDL-2015: TALYS-based evaluated nuclear data library.