Ⅰ. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 52 (2019)

Activation cross sections of α-induced reactions on nat Zn for Ge andGa production†
M. Aikawa,∗1,∗2 M. Saito,∗3,∗2,∗4 S. Ebata,∗1,∗5 Y. Komori,∗2 and H. Haba∗2
Gallium-68 (T1/2 = 67.71 min) is used in positronemission tomography (PET). The production of 68 Ga
is important for its application in PET. In addition
to 68 Ga, the production of its long-lived parent, 68 Ge(T1/2 = 270.95 d), is worthy of investigation for a 68 Ga
generator. One of the reactions to produce 68 Ge is the
α-induced reaction on nat Zn. Two sets of experimental data1,2) could be found in the EXchange FORmat(EXFOR) library. The two datasets deviate from eachother. Therefore, we measured the cross sections of
α-induced reactions on nat Zn for 68 Ge production.
The experiment was performed at the AVF cyclotronof the RIKEN RI Beam Factory using standard methods, stacked foil activation method, and oﬀ-line γ-ray
spectrometry. Thin metallic foils of nat Zn (99.9% purity, Nilaco Corp., Japan) and nat Ti (99.6% purity, Nilaco Corp., Japan) were stacked as the target. The
stacked target was irradiated by a 51.5 MeV α beam.
The incident beam energy was measured by the timeof-ﬂight method using a plastic scintillator monitor.3)
The irradiation of the α beam lasted for 2 hours. The
average intensity was 82.0 nA, which was measured bya Faraday cup. The decrease in the energy of projectiles in the target was estimated using the SRIM
code.4) γ spectra from the irradiated foils were measured with a high-resolution HPGe detector.
To assess the beam parameters and target thicknesses, the cross sections of the nat Ti(α, x)51 Cr monitor reaction were derived. Consequently, we could conﬁrm that our results were signiﬁcantly consistent withthe recommended values.5)
The 1077.34-keV γ-line (Iγ = 3.22%) from the 68 Ga
decay was measured after a long cooling time of approximately 80 days. Directly produced 68 Ga could
completely get decayed in this period and the decay of68
Ga was in equilibrium with that of its parent 68 Ge.
The cross sections of 68 Ge are shown in Fig. 1 with previous experimental data1,2) and TENDL-2017 data.6)
The peak position of our result is consistent with theexperimental data, although the amplitude is slightlylarger. The tendency of TENDL-2017 data is diﬀerent
from the experimental data.
The integral yield of 68 Ge was estimated from the†
∗1
∗2
∗3
∗4
∗5nat

Cross section (mb)250

Haasbroek+ (1976)
Nagame+ (1978)
TENDL2017
This workZn(α,x)68Ge

200
150
10050
00

1020

30

4050

Energy (MeV)

Fig. 1. Excitation function of nat Zn(α, x)68 Ge reaction.

Integral yield (kBq/µAh)

10068Haasbroek+ (1976)
Nagame+ (1978)
This work

Ge8060402001015202530 35 40
Energy (MeV)

455055Fig. 2. Integral yield of 68 Ge.

cross sections measured in this work and stopping powers calculated by the SRIM code.4) The derived integral yield is shown in Fig. 2 with the previously obtained experimental data.1,2) The values obtained inour result are greater than other data above 30 MeV
as expected from the cross sections measured in thiswork.
References
1) F. J. Haasbroek et al., CSIR Res. Rep. FIS 91, 1 (1976).
2) Y. Nagame et al., Int. J. Appl. Radiat. Isot. 29, 615(1978).
3) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC2014), 3566 (2014).
4) SRIM: the Stopping and Range of Ions in Matter, http://www.srim.org/.
5) A. Hermanne et al., Nucl. Data Sheets 148, 338 (2017).
6) A. J. Koning et al., Nucl. Data Sheets 113, 2841 (2012).

Condensed from the article in Nucl. Instrum. Methods Phys.
Res. B 427, 91 (2018)
Faculty of Science, Hokkaido University
RIKEN Nishina Center
Graduate School of Science, Hokkaido University
Present address: Graduate School of Biomedical Science,
Hokkaido University
Present address: School of Environment and Society, Tokyo
Institute of Technology- 23 -